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rust/bench_data/glorious_old_parser
Aleksey Kladov 61f15b72ac Add parsing benchmark
2021-02-09 21:52:34 +03:00

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use crate::ast::{AngleBracketedArgs, ParenthesizedArgs, AttrStyle, BareFnTy};
use crate::ast::{GenericBound, TraitBoundModifier};
use crate::ast::Unsafety;
use crate::ast::{Mod, AnonConst, Arg, Arm, Guard, Attribute, BindingMode, TraitItemKind};
use crate::ast::Block;
use crate::ast::{BlockCheckMode, CaptureBy, Movability};
use crate::ast::{Constness, Crate};
use crate::ast::Defaultness;
use crate::ast::EnumDef;
use crate::ast::{Expr, ExprKind, RangeLimits};
use crate::ast::{Field, FnDecl, FnHeader};
use crate::ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
use crate::ast::{GenericParam, GenericParamKind};
use crate::ast::GenericArg;
use crate::ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind};
use crate::ast::{Label, Lifetime, Lit, LitKind};
use crate::ast::Local;
use crate::ast::MacStmtStyle;
use crate::ast::{Mac, Mac_, MacDelimiter};
use crate::ast::{MutTy, Mutability};
use crate::ast::{Pat, PatKind, PathSegment};
use crate::ast::{PolyTraitRef, QSelf};
use crate::ast::{Stmt, StmtKind};
use crate::ast::{VariantData, StructField};
use crate::ast::StrStyle;
use crate::ast::SelfKind;
use crate::ast::{TraitItem, TraitRef, TraitObjectSyntax};
use crate::ast::{Ty, TyKind, TypeBinding, GenericBounds};
use crate::ast::{Visibility, VisibilityKind, WhereClause, CrateSugar};
use crate::ast::{UseTree, UseTreeKind};
use crate::ast::{BinOpKind, UnOp};
use crate::ast::{RangeEnd, RangeSyntax};
use crate::{ast, attr};
use crate::ext::base::DummyResult;
use crate::source_map::{self, SourceMap, Spanned, respan};
use crate::parse::{self, SeqSep, classify, token};
use crate::parse::lexer::{TokenAndSpan, UnmatchedBrace};
use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
use crate::parse::token::DelimToken;
use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
use crate::util::parser::{AssocOp, Fixity};
use crate::print::pprust;
use crate::ptr::P;
use crate::parse::PResult;
use crate::ThinVec;
use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
use crate::symbol::{Symbol, keywords};
use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
use rustc_target::spec::abi::{self, Abi};
use syntax_pos::{Span, MultiSpan, BytePos, FileName};
use log::{debug, trace};
use std::borrow::Cow;
use std::cmp;
use std::mem;
use std::path::{self, Path, PathBuf};
use std::slice;
#[derive(Debug)]
/// Whether the type alias or associated type is a concrete type or an existential type
pub enum AliasKind {
/// Just a new name for the same type
Weak(P<Ty>),
/// Only trait impls of the type will be usable, not the actual type itself
Existential(GenericBounds),
}
bitflags::bitflags! {
struct Restrictions: u8 {
const STMT_EXPR = 1 << 0;
const NO_STRUCT_LITERAL = 1 << 1;
}
}
type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
/// Specifies how to parse a path.
#[derive(Copy, Clone, PartialEq)]
pub enum PathStyle {
/// In some contexts, notably in expressions, paths with generic arguments are ambiguous
/// with something else. For example, in expressions `segment < ....` can be interpreted
/// as a comparison and `segment ( ....` can be interpreted as a function call.
/// In all such contexts the non-path interpretation is preferred by default for practical
/// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
/// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
Expr,
/// In other contexts, notably in types, no ambiguity exists and paths can be written
/// without the disambiguator, e.g., `x<y>` - unambiguously a path.
/// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
Type,
/// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
/// visibilities or attributes.
/// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
/// (paths in "mod" contexts have to be checked later for absence of generic arguments
/// anyway, due to macros), but it is used to avoid weird suggestions about expected
/// tokens when something goes wrong.
Mod,
}
#[derive(Clone, Copy, PartialEq, Debug)]
enum SemiColonMode {
Break,
Ignore,
Comma,
}
#[derive(Clone, Copy, PartialEq, Debug)]
enum BlockMode {
Break,
Ignore,
}
/// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
/// dropped into the token stream, which happens while parsing the result of
/// macro expansion). Placement of these is not as complex as I feared it would
/// be. The important thing is to make sure that lookahead doesn't balk at
/// `token::Interpolated` tokens.
macro_rules! maybe_whole_expr {
($p:expr) => {
if let token::Interpolated(nt) = $p.token.clone() {
match *nt {
token::NtExpr(ref e) | token::NtLiteral(ref e) => {
$p.bump();
return Ok((*e).clone());
}
token::NtPath(ref path) => {
$p.bump();
let span = $p.span;
let kind = ExprKind::Path(None, (*path).clone());
return Ok($p.mk_expr(span, kind, ThinVec::new()));
}
token::NtBlock(ref block) => {
$p.bump();
let span = $p.span;
let kind = ExprKind::Block((*block).clone(), None);
return Ok($p.mk_expr(span, kind, ThinVec::new()));
}
_ => {},
};
}
}
}
/// As maybe_whole_expr, but for things other than expressions
macro_rules! maybe_whole {
($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
if let token::Interpolated(nt) = $p.token.clone() {
if let token::$constructor($x) = (*nt).clone() {
$p.bump();
return Ok($e);
}
}
};
}
fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> {
if let Some(ref mut rhs) = rhs {
lhs.append(rhs);
}
lhs
}
#[derive(Debug, Clone, Copy, PartialEq)]
enum PrevTokenKind {
DocComment,
Comma,
Plus,
Interpolated,
Eof,
Ident,
Other,
}
trait RecoverQPath: Sized {
const PATH_STYLE: PathStyle = PathStyle::Expr;
fn to_ty(&self) -> Option<P<Ty>>;
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self;
fn to_string(&self) -> String;
}
impl RecoverQPath for Ty {
const PATH_STYLE: PathStyle = PathStyle::Type;
fn to_ty(&self) -> Option<P<Ty>> {
Some(P(self.clone()))
}
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: TyKind::Path(qself, path), id: self.id }
}
fn to_string(&self) -> String {
pprust::ty_to_string(self)
}
}
impl RecoverQPath for Pat {
fn to_ty(&self) -> Option<P<Ty>> {
self.to_ty()
}
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: PatKind::Path(qself, path), id: self.id }
}
fn to_string(&self) -> String {
pprust::pat_to_string(self)
}
}
impl RecoverQPath for Expr {
fn to_ty(&self) -> Option<P<Ty>> {
self.to_ty()
}
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: ExprKind::Path(qself, path),
id: self.id, attrs: self.attrs.clone() }
}
fn to_string(&self) -> String {
pprust::expr_to_string(self)
}
}
/* ident is handled by common.rs */
#[derive(Clone)]
pub struct Parser<'a> {
pub sess: &'a ParseSess,
/// the current token:
pub token: token::Token,
/// the span of the current token:
pub span: Span,
/// the span of the previous token:
meta_var_span: Option<Span>,
pub prev_span: Span,
/// the previous token kind
prev_token_kind: PrevTokenKind,
restrictions: Restrictions,
/// Used to determine the path to externally loaded source files
crate directory: Directory<'a>,
/// Whether to parse sub-modules in other files.
pub recurse_into_file_modules: bool,
/// Name of the root module this parser originated from. If `None`, then the
/// name is not known. This does not change while the parser is descending
/// into modules, and sub-parsers have new values for this name.
pub root_module_name: Option<String>,
crate expected_tokens: Vec<TokenType>,
token_cursor: TokenCursor,
desugar_doc_comments: bool,
/// Whether we should configure out of line modules as we parse.
pub cfg_mods: bool,
/// This field is used to keep track of how many left angle brackets we have seen. This is
/// required in order to detect extra leading left angle brackets (`<` characters) and error
/// appropriately.
///
/// See the comments in the `parse_path_segment` function for more details.
crate unmatched_angle_bracket_count: u32,
crate max_angle_bracket_count: u32,
/// List of all unclosed delimiters found by the lexer. If an entry is used for error recovery
/// it gets removed from here. Every entry left at the end gets emitted as an independent
/// error.
crate unclosed_delims: Vec<UnmatchedBrace>,
}
#[derive(Clone)]
struct TokenCursor {
frame: TokenCursorFrame,
stack: Vec<TokenCursorFrame>,
}
#[derive(Clone)]
struct TokenCursorFrame {
delim: token::DelimToken,
span: DelimSpan,
open_delim: bool,
tree_cursor: tokenstream::Cursor,
close_delim: bool,
last_token: LastToken,
}
/// This is used in `TokenCursorFrame` above to track tokens that are consumed
/// by the parser, and then that's transitively used to record the tokens that
/// each parse AST item is created with.
///
/// Right now this has two states, either collecting tokens or not collecting
/// tokens. If we're collecting tokens we just save everything off into a local
/// `Vec`. This should eventually though likely save tokens from the original
/// token stream and just use slicing of token streams to avoid creation of a
/// whole new vector.
///
/// The second state is where we're passively not recording tokens, but the last
/// token is still tracked for when we want to start recording tokens. This
/// "last token" means that when we start recording tokens we'll want to ensure
/// that this, the first token, is included in the output.
///
/// You can find some more example usage of this in the `collect_tokens` method
/// on the parser.
#[derive(Clone)]
enum LastToken {
Collecting(Vec<TreeAndJoint>),
Was(Option<TreeAndJoint>),
}
impl TokenCursorFrame {
fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
TokenCursorFrame {
delim: delim,
span: sp,
open_delim: delim == token::NoDelim,
tree_cursor: tts.clone().into_trees(),
close_delim: delim == token::NoDelim,
last_token: LastToken::Was(None),
}
}
}
impl TokenCursor {
fn next(&mut self) -> TokenAndSpan {
loop {
let tree = if !self.frame.open_delim {
self.frame.open_delim = true;
TokenTree::open_tt(self.frame.span.open, self.frame.delim)
} else if let Some(tree) = self.frame.tree_cursor.next() {
tree
} else if !self.frame.close_delim {
self.frame.close_delim = true;
TokenTree::close_tt(self.frame.span.close, self.frame.delim)
} else if let Some(frame) = self.stack.pop() {
self.frame = frame;
continue
} else {
return TokenAndSpan { tok: token::Eof, sp: syntax_pos::DUMMY_SP }
};
match self.frame.last_token {
LastToken::Collecting(ref mut v) => v.push(tree.clone().into()),
LastToken::Was(ref mut t) => *t = Some(tree.clone().into()),
}
match tree {
TokenTree::Token(sp, tok) => return TokenAndSpan { tok: tok, sp: sp },
TokenTree::Delimited(sp, delim, tts) => {
let frame = TokenCursorFrame::new(sp, delim, &tts);
self.stack.push(mem::replace(&mut self.frame, frame));
}
}
}
}
fn next_desugared(&mut self) -> TokenAndSpan {
let (sp, name) = match self.next() {
TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, name),
tok => return tok,
};
let stripped = strip_doc_comment_decoration(&name.as_str());
// Searches for the occurrences of `"#*` and returns the minimum number of `#`s
// required to wrap the text.
let mut num_of_hashes = 0;
let mut count = 0;
for ch in stripped.chars() {
count = match ch {
'"' => 1,
'#' if count > 0 => count + 1,
_ => 0,
};
num_of_hashes = cmp::max(num_of_hashes, count);
}
let delim_span = DelimSpan::from_single(sp);
let body = TokenTree::Delimited(
delim_span,
token::Bracket,
[TokenTree::Token(sp, token::Ident(ast::Ident::from_str("doc"), false)),
TokenTree::Token(sp, token::Eq),
TokenTree::Token(sp, token::Literal(
token::StrRaw(Symbol::intern(&stripped), num_of_hashes), None))
]
.iter().cloned().collect::<TokenStream>().into(),
);
self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new(
delim_span,
token::NoDelim,
&if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
[TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body]
.iter().cloned().collect::<TokenStream>().into()
} else {
[TokenTree::Token(sp, token::Pound), body]
.iter().cloned().collect::<TokenStream>().into()
},
)));
self.next()
}
}
#[derive(Clone, PartialEq)]
crate enum TokenType {
Token(token::Token),
Keyword(keywords::Keyword),
Operator,
Lifetime,
Ident,
Path,
Type,
Const,
}
impl TokenType {
fn to_string(&self) -> String {
match *self {
TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)),
TokenType::Keyword(kw) => format!("`{}`", kw.name()),
TokenType::Operator => "an operator".to_string(),
TokenType::Lifetime => "lifetime".to_string(),
TokenType::Ident => "identifier".to_string(),
TokenType::Path => "path".to_string(),
TokenType::Type => "type".to_string(),
TokenType::Const => "const".to_string(),
}
}
}
/// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
/// `IDENT<<u8 as Trait>::AssocTy>`.
///
/// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
/// that `IDENT` is not the ident of a fn trait.
fn can_continue_type_after_non_fn_ident(t: &token::Token) -> bool {
t == &token::ModSep || t == &token::Lt ||
t == &token::BinOp(token::Shl)
}
/// Information about the path to a module.
pub struct ModulePath {
name: String,
path_exists: bool,
pub result: Result<ModulePathSuccess, Error>,
}
pub struct ModulePathSuccess {
pub path: PathBuf,
pub directory_ownership: DirectoryOwnership,
warn: bool,
}
pub enum Error {
FileNotFoundForModule {
mod_name: String,
default_path: String,
secondary_path: String,
dir_path: String,
},
DuplicatePaths {
mod_name: String,
default_path: String,
secondary_path: String,
},
UselessDocComment,
InclusiveRangeWithNoEnd,
}
impl Error {
fn span_err<S: Into<MultiSpan>>(self,
sp: S,
handler: &errors::Handler) -> DiagnosticBuilder<'_> {
match self {
Error::FileNotFoundForModule { ref mod_name,
ref default_path,
ref secondary_path,
ref dir_path } => {
let mut err = struct_span_err!(handler, sp, E0583,
"file not found for module `{}`", mod_name);
err.help(&format!("name the file either {} or {} inside the directory \"{}\"",
default_path,
secondary_path,
dir_path));
err
}
Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
let mut err = struct_span_err!(handler, sp, E0584,
"file for module `{}` found at both {} and {}",
mod_name,
default_path,
secondary_path);
err.help("delete or rename one of them to remove the ambiguity");
err
}
Error::UselessDocComment => {
let mut err = struct_span_err!(handler, sp, E0585,
"found a documentation comment that doesn't document anything");
err.help("doc comments must come before what they document, maybe a comment was \
intended with `//`?");
err
}
Error::InclusiveRangeWithNoEnd => {
let mut err = struct_span_err!(handler, sp, E0586,
"inclusive range with no end");
err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)");
err
}
}
}
}
#[derive(Debug)]
enum LhsExpr {
NotYetParsed,
AttributesParsed(ThinVec<Attribute>),
AlreadyParsed(P<Expr>),
}
impl From<Option<ThinVec<Attribute>>> for LhsExpr {
fn from(o: Option<ThinVec<Attribute>>) -> Self {
if let Some(attrs) = o {
LhsExpr::AttributesParsed(attrs)
} else {
LhsExpr::NotYetParsed
}
}
}
impl From<P<Expr>> for LhsExpr {
fn from(expr: P<Expr>) -> Self {
LhsExpr::AlreadyParsed(expr)
}
}
/// Creates a placeholder argument.
fn dummy_arg(span: Span) -> Arg {
let ident = Ident::new(keywords::Invalid.name(), span);
let pat = P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
span,
});
let ty = Ty {
node: TyKind::Err,
span,
id: ast::DUMMY_NODE_ID
};
Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID }
}
#[derive(Copy, Clone, Debug)]
enum TokenExpectType {
Expect,
NoExpect,
}
impl<'a> Parser<'a> {
pub fn new(sess: &'a ParseSess,
tokens: TokenStream,
directory: Option<Directory<'a>>,
recurse_into_file_modules: bool,
desugar_doc_comments: bool)
-> Self {
let mut parser = Parser {
sess,
token: token::Whitespace,
span: syntax_pos::DUMMY_SP,
prev_span: syntax_pos::DUMMY_SP,
meta_var_span: None,
prev_token_kind: PrevTokenKind::Other,
restrictions: Restrictions::empty(),
recurse_into_file_modules,
directory: Directory {
path: Cow::from(PathBuf::new()),
ownership: DirectoryOwnership::Owned { relative: None }
},
root_module_name: None,
expected_tokens: Vec::new(),
token_cursor: TokenCursor {
frame: TokenCursorFrame::new(
DelimSpan::dummy(),
token::NoDelim,
&tokens.into(),
),
stack: Vec::new(),
},
desugar_doc_comments,
cfg_mods: true,
unmatched_angle_bracket_count: 0,
max_angle_bracket_count: 0,
unclosed_delims: Vec::new(),
};
let tok = parser.next_tok();
parser.token = tok.tok;
parser.span = tok.sp;
if let Some(directory) = directory {
parser.directory = directory;
} else if !parser.span.is_dummy() {
if let FileName::Real(mut path) = sess.source_map().span_to_unmapped_path(parser.span) {
path.pop();
parser.directory.path = Cow::from(path);
}
}
parser.process_potential_macro_variable();
parser
}
fn next_tok(&mut self) -> TokenAndSpan {
let mut next = if self.desugar_doc_comments {
self.token_cursor.next_desugared()
} else {
self.token_cursor.next()
};
if next.sp.is_dummy() {
// Tweak the location for better diagnostics, but keep syntactic context intact.
next.sp = self.prev_span.with_ctxt(next.sp.ctxt());
}
next
}
/// Converts the current token to a string using `self`'s reader.
pub fn this_token_to_string(&self) -> String {
pprust::token_to_string(&self.token)
}
fn token_descr(&self) -> Option<&'static str> {
Some(match &self.token {
t if t.is_special_ident() => "reserved identifier",
t if t.is_used_keyword() => "keyword",
t if t.is_unused_keyword() => "reserved keyword",
token::DocComment(..) => "doc comment",
_ => return None,
})
}
fn this_token_descr(&self) -> String {
if let Some(prefix) = self.token_descr() {
format!("{} `{}`", prefix, self.this_token_to_string())
} else {
format!("`{}`", self.this_token_to_string())
}
}
fn unexpected_last<T>(&self, t: &token::Token) -> PResult<'a, T> {
let token_str = pprust::token_to_string(t);
Err(self.span_fatal(self.prev_span, &format!("unexpected token: `{}`", token_str)))
}
crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
match self.expect_one_of(&[], &[]) {
Err(e) => Err(e),
Ok(_) => unreachable!(),
}
}
/// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
pub fn expect(&mut self, t: &token::Token) -> PResult<'a, bool /* recovered */> {
if self.expected_tokens.is_empty() {
if self.token == *t {
self.bump();
Ok(false)
} else {
let token_str = pprust::token_to_string(t);
let this_token_str = self.this_token_descr();
let mut err = self.fatal(&format!("expected `{}`, found {}",
token_str,
this_token_str));
let sp = if self.token == token::Token::Eof {
// EOF, don't want to point at the following char, but rather the last token
self.prev_span
} else {
self.sess.source_map().next_point(self.prev_span)
};
let label_exp = format!("expected `{}`", token_str);
match self.recover_closing_delimiter(&[t.clone()], err) {
Err(e) => err = e,
Ok(recovered) => {
return Ok(recovered);
}
}
let cm = self.sess.source_map();
match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
(Ok(ref a), Ok(ref b)) if a.line == b.line => {
// When the spans are in the same line, it means that the only content
// between them is whitespace, point only at the found token.
err.span_label(self.span, label_exp);
}
_ => {
err.span_label(sp, label_exp);
err.span_label(self.span, "unexpected token");
}
}
Err(err)
}
} else {
self.expect_one_of(slice::from_ref(t), &[])
}
}
fn recover_closing_delimiter(
&mut self,
tokens: &[token::Token],
mut err: DiagnosticBuilder<'a>,
) -> PResult<'a, bool> {
let mut pos = None;
// we want to use the last closing delim that would apply
for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
&& Some(self.span) > unmatched.unclosed_span
{
pos = Some(i);
}
}
match pos {
Some(pos) => {
// Recover and assume that the detected unclosed delimiter was meant for
// this location. Emit the diagnostic and act as if the delimiter was
// present for the parser's sake.
// Don't attempt to recover from this unclosed delimiter more than once.
let unmatched = self.unclosed_delims.remove(pos);
let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
// We want to suggest the inclusion of the closing delimiter where it makes
// the most sense, which is immediately after the last token:
//
// {foo(bar {}}
// - ^
// | |
// | help: `)` may belong here (FIXME: #58270)
// |
// unclosed delimiter
if let Some(sp) = unmatched.unclosed_span {
err.span_label(sp, "unclosed delimiter");
}
err.span_suggestion_short(
self.sess.source_map().next_point(self.prev_span),
&format!("{} may belong here", delim.to_string()),
delim.to_string(),
Applicability::MaybeIncorrect,
);
err.emit();
self.expected_tokens.clear(); // reduce errors
Ok(true)
}
_ => Err(err),
}
}
/// Expect next token to be edible or inedible token. If edible,
/// then consume it; if inedible, then return without consuming
/// anything. Signal a fatal error if next token is unexpected.
pub fn expect_one_of(
&mut self,
edible: &[token::Token],
inedible: &[token::Token],
) -> PResult<'a, bool /* recovered */> {
fn tokens_to_string(tokens: &[TokenType]) -> String {
let mut i = tokens.iter();
// This might be a sign we need a connect method on Iterator.
let b = i.next()
.map_or(String::new(), |t| t.to_string());
i.enumerate().fold(b, |mut b, (i, a)| {
if tokens.len() > 2 && i == tokens.len() - 2 {
b.push_str(", or ");
} else if tokens.len() == 2 && i == tokens.len() - 2 {
b.push_str(" or ");
} else {
b.push_str(", ");
}
b.push_str(&a.to_string());
b
})
}
if edible.contains(&self.token) {
self.bump();
Ok(false)
} else if inedible.contains(&self.token) {
// leave it in the input
Ok(false)
} else {
let mut expected = edible.iter()
.map(|x| TokenType::Token(x.clone()))
.chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
.chain(self.expected_tokens.iter().cloned())
.collect::<Vec<_>>();
expected.sort_by_cached_key(|x| x.to_string());
expected.dedup();
let expect = tokens_to_string(&expected[..]);
let actual = self.this_token_to_string();
let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
let short_expect = if expected.len() > 6 {
format!("{} possible tokens", expected.len())
} else {
expect.clone()
};
(format!("expected one of {}, found `{}`", expect, actual),
(self.sess.source_map().next_point(self.prev_span),
format!("expected one of {} here", short_expect)))
} else if expected.is_empty() {
(format!("unexpected token: `{}`", actual),
(self.prev_span, "unexpected token after this".to_string()))
} else {
(format!("expected {}, found `{}`", expect, actual),
(self.sess.source_map().next_point(self.prev_span),
format!("expected {} here", expect)))
};
let mut err = self.fatal(&msg_exp);
if self.token.is_ident_named("and") {
err.span_suggestion_short(
self.span,
"use `&&` instead of `and` for the boolean operator",
"&&".to_string(),
Applicability::MaybeIncorrect,
);
}
if self.token.is_ident_named("or") {
err.span_suggestion_short(
self.span,
"use `||` instead of `or` for the boolean operator",
"||".to_string(),
Applicability::MaybeIncorrect,
);
}
let sp = if self.token == token::Token::Eof {
// This is EOF, don't want to point at the following char, but rather the last token
self.prev_span
} else {
label_sp
};
match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt {
TokenType::Token(t) => Some(t.clone()),
_ => None,
}).collect::<Vec<_>>(), err) {
Err(e) => err = e,
Ok(recovered) => {
return Ok(recovered);
}
}
let cm = self.sess.source_map();
match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
(Ok(ref a), Ok(ref b)) if a.line == b.line => {
// When the spans are in the same line, it means that the only content between
// them is whitespace, point at the found token in that case:
//
// X | () => { syntax error };
// | ^^^^^ expected one of 8 possible tokens here
//
// instead of having:
//
// X | () => { syntax error };
// | -^^^^^ unexpected token
// | |
// | expected one of 8 possible tokens here
err.span_label(self.span, label_exp);
}
_ if self.prev_span == syntax_pos::DUMMY_SP => {
// Account for macro context where the previous span might not be
// available to avoid incorrect output (#54841).
err.span_label(self.span, "unexpected token");
}
_ => {
err.span_label(sp, label_exp);
err.span_label(self.span, "unexpected token");
}
}
Err(err)
}
}
/// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
fn interpolated_or_expr_span(&self,
expr: PResult<'a, P<Expr>>)
-> PResult<'a, (Span, P<Expr>)> {
expr.map(|e| {
if self.prev_token_kind == PrevTokenKind::Interpolated {
(self.prev_span, e)
} else {
(e.span, e)
}
})
}
fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
let mut err = self.struct_span_err(self.span,
&format!("expected identifier, found {}",
self.this_token_descr()));
if let token::Ident(ident, false) = &self.token {
if ident.is_reserved() && !ident.is_path_segment_keyword() &&
ident.name != keywords::Underscore.name()
{
err.span_suggestion(
self.span,
"you can escape reserved keywords to use them as identifiers",
format!("r#{}", ident),
Applicability::MaybeIncorrect,
);
}
}
if let Some(token_descr) = self.token_descr() {
err.span_label(self.span, format!("expected identifier, found {}", token_descr));
} else {
err.span_label(self.span, "expected identifier");
if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
err.span_suggestion(
self.span,
"remove this comma",
String::new(),
Applicability::MachineApplicable,
);
}
}
err
}
pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
self.parse_ident_common(true)
}
fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
match self.token {
token::Ident(ident, _) => {
if self.token.is_reserved_ident() {
let mut err = self.expected_ident_found();
if recover {
err.emit();
} else {
return Err(err);
}
}
let span = self.span;
self.bump();
Ok(Ident::new(ident.name, span))
}
_ => {
Err(if self.prev_token_kind == PrevTokenKind::DocComment {
self.span_fatal_err(self.prev_span, Error::UselessDocComment)
} else {
self.expected_ident_found()
})
}
}
}
/// Checks if the next token is `tok`, and returns `true` if so.
///
/// This method will automatically add `tok` to `expected_tokens` if `tok` is not
/// encountered.
crate fn check(&mut self, tok: &token::Token) -> bool {
let is_present = self.token == *tok;
if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
is_present
}
/// Consumes a token 'tok' if it exists. Returns whether the given token was present.
pub fn eat(&mut self, tok: &token::Token) -> bool {
let is_present = self.check(tok);
if is_present { self.bump() }
is_present
}
fn check_keyword(&mut self, kw: keywords::Keyword) -> bool {
self.expected_tokens.push(TokenType::Keyword(kw));
self.token.is_keyword(kw)
}
/// If the next token is the given keyword, eats it and returns
/// `true`. Otherwise, returns `false`.
pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool {
if self.check_keyword(kw) {
self.bump();
true
} else {
false
}
}
fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> bool {
if self.token.is_keyword(kw) {
self.bump();
true
} else {
false
}
}
/// If the given word is not a keyword, signals an error.
/// If the next token is not the given word, signals an error.
/// Otherwise, eats it.
fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<'a, ()> {
if !self.eat_keyword(kw) {
self.unexpected()
} else {
Ok(())
}
}
fn check_ident(&mut self) -> bool {
if self.token.is_ident() {
true
} else {
self.expected_tokens.push(TokenType::Ident);
false
}
}
fn check_path(&mut self) -> bool {
if self.token.is_path_start() {
true
} else {
self.expected_tokens.push(TokenType::Path);
false
}
}
fn check_type(&mut self) -> bool {
if self.token.can_begin_type() {
true
} else {
self.expected_tokens.push(TokenType::Type);
false
}
}
fn check_const_arg(&mut self) -> bool {
if self.token.can_begin_const_arg() {
true
} else {
self.expected_tokens.push(TokenType::Const);
false
}
}
/// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=`
/// and continues. If a `+` is not seen, returns `false`.
///
/// This is used when token-splitting `+=` into `+`.
/// See issue #47856 for an example of when this may occur.
fn eat_plus(&mut self) -> bool {
self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
match self.token {
token::BinOp(token::Plus) => {
self.bump();
true
}
token::BinOpEq(token::Plus) => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
self.bump_with(token::Eq, span);
true
}
_ => false,
}
}
/// Checks to see if the next token is either `+` or `+=`.
/// Otherwise returns `false`.
fn check_plus(&mut self) -> bool {
if self.token.is_like_plus() {
true
}
else {
self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
false
}
}
/// Expects and consumes an `&`. If `&&` is seen, replaces it with a single
/// `&` and continues. If an `&` is not seen, signals an error.
fn expect_and(&mut self) -> PResult<'a, ()> {
self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
match self.token {
token::BinOp(token::And) => {
self.bump();
Ok(())
}
token::AndAnd => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
Ok(self.bump_with(token::BinOp(token::And), span))
}
_ => self.unexpected()
}
}
/// Expects and consumes an `|`. If `||` is seen, replaces it with a single
/// `|` and continues. If an `|` is not seen, signals an error.
fn expect_or(&mut self) -> PResult<'a, ()> {
self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
match self.token {
token::BinOp(token::Or) => {
self.bump();
Ok(())
}
token::OrOr => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
Ok(self.bump_with(token::BinOp(token::Or), span))
}
_ => self.unexpected()
}
}
fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
match suffix {
None => {/* everything ok */}
Some(suf) => {
let text = suf.as_str();
if text.is_empty() {
self.span_bug(sp, "found empty literal suffix in Some")
}
let msg = format!("{} with a suffix is invalid", kind);
self.struct_span_err(sp, &msg)
.span_label(sp, msg)
.emit();
}
}
}
/// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
/// `<` and continue. If `<-` is seen, replaces it with a single `<`
/// and continue. If a `<` is not seen, returns false.
///
/// This is meant to be used when parsing generics on a path to get the
/// starting token.
fn eat_lt(&mut self) -> bool {
self.expected_tokens.push(TokenType::Token(token::Lt));
let ate = match self.token {
token::Lt => {
self.bump();
true
}
token::BinOp(token::Shl) => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
self.bump_with(token::Lt, span);
true
}
token::LArrow => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
self.bump_with(token::BinOp(token::Minus), span);
true
}
_ => false,
};
if ate {
// See doc comment for `unmatched_angle_bracket_count`.
self.unmatched_angle_bracket_count += 1;
self.max_angle_bracket_count += 1;
debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
}
ate
}
fn expect_lt(&mut self) -> PResult<'a, ()> {
if !self.eat_lt() {
self.unexpected()
} else {
Ok(())
}
}
/// Expects and consumes a single `>` token. if a `>>` is seen, replaces it
/// with a single `>` and continues. If a `>` is not seen, signals an error.
fn expect_gt(&mut self) -> PResult<'a, ()> {
self.expected_tokens.push(TokenType::Token(token::Gt));
let ate = match self.token {
token::Gt => {
self.bump();
Some(())
}
token::BinOp(token::Shr) => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
Some(self.bump_with(token::Gt, span))
}
token::BinOpEq(token::Shr) => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
Some(self.bump_with(token::Ge, span))
}
token::Ge => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
Some(self.bump_with(token::Eq, span))
}
_ => None,
};
match ate {
Some(_) => {
// See doc comment for `unmatched_angle_bracket_count`.
if self.unmatched_angle_bracket_count > 0 {
self.unmatched_angle_bracket_count -= 1;
debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
}
Ok(())
},
None => self.unexpected(),
}
}
/// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
/// passes through any errors encountered. Used for error recovery.
fn eat_to_tokens(&mut self, kets: &[&token::Token]) {
let handler = self.diagnostic();
if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets,
SeqSep::none(),
TokenExpectType::Expect,
|p| Ok(p.parse_token_tree())) {
handler.cancel(err);
}
}
/// Parses a sequence, including the closing delimiter. The function
/// `f` must consume tokens until reaching the next separator or
/// closing bracket.
pub fn parse_seq_to_end<T, F>(&mut self,
ket: &token::Token,
sep: SeqSep,
f: F)
-> PResult<'a, Vec<T>> where
F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
{
let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
if !recovered {
self.bump();
}
Ok(val)
}
/// Parses a sequence, not including the closing delimiter. The function
/// `f` must consume tokens until reaching the next separator or
/// closing bracket.
pub fn parse_seq_to_before_end<T, F>(
&mut self,
ket: &token::Token,
sep: SeqSep,
f: F,
) -> PResult<'a, (Vec<T>, bool)>
where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
{
self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
}
fn parse_seq_to_before_tokens<T, F>(
&mut self,
kets: &[&token::Token],
sep: SeqSep,
expect: TokenExpectType,
mut f: F,
) -> PResult<'a, (Vec<T>, bool /* recovered */)>
where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
{
let mut first = true;
let mut recovered = false;
let mut v = vec![];
while !kets.iter().any(|k| {
match expect {
TokenExpectType::Expect => self.check(k),
TokenExpectType::NoExpect => self.token == **k,
}
}) {
match self.token {
token::CloseDelim(..) | token::Eof => break,
_ => {}
};
if let Some(ref t) = sep.sep {
if first {
first = false;
} else {
match self.expect(t) {
Ok(false) => {}
Ok(true) => {
recovered = true;
break;
}
Err(mut e) => {
// Attempt to keep parsing if it was a similar separator
if let Some(ref tokens) = t.similar_tokens() {
if tokens.contains(&self.token) {
self.bump();
}
}
e.emit();
// Attempt to keep parsing if it was an omitted separator
match f(self) {
Ok(t) => {
v.push(t);
continue;
},
Err(mut e) => {
e.cancel();
break;
}
}
}
}
}
}
if sep.trailing_sep_allowed && kets.iter().any(|k| {
match expect {
TokenExpectType::Expect => self.check(k),
TokenExpectType::NoExpect => self.token == **k,
}
}) {
break;
}
let t = f(self)?;
v.push(t);
}
Ok((v, recovered))
}
/// Parses a sequence, including the closing delimiter. The function
/// `f` must consume tokens until reaching the next separator or
/// closing bracket.
fn parse_unspanned_seq<T, F>(
&mut self,
bra: &token::Token,
ket: &token::Token,
sep: SeqSep,
f: F,
) -> PResult<'a, Vec<T>> where
F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
{
self.expect(bra)?;
let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
if !recovered {
self.eat(ket);
}
Ok(result)
}
/// Advance the parser by one token
pub fn bump(&mut self) {
if self.prev_token_kind == PrevTokenKind::Eof {
// Bumping after EOF is a bad sign, usually an infinite loop.
self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
}
self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
// Record last token kind for possible error recovery.
self.prev_token_kind = match self.token {
token::DocComment(..) => PrevTokenKind::DocComment,
token::Comma => PrevTokenKind::Comma,
token::BinOp(token::Plus) => PrevTokenKind::Plus,
token::Interpolated(..) => PrevTokenKind::Interpolated,
token::Eof => PrevTokenKind::Eof,
token::Ident(..) => PrevTokenKind::Ident,
_ => PrevTokenKind::Other,
};
let next = self.next_tok();
self.span = next.sp;
self.token = next.tok;
self.expected_tokens.clear();
// check after each token
self.process_potential_macro_variable();
}
/// Advance the parser using provided token as a next one. Use this when
/// consuming a part of a token. For example a single `<` from `<<`.
fn bump_with(&mut self, next: token::Token, span: Span) {
self.prev_span = self.span.with_hi(span.lo());
// It would be incorrect to record the kind of the current token, but
// fortunately for tokens currently using `bump_with`, the
// prev_token_kind will be of no use anyway.
self.prev_token_kind = PrevTokenKind::Other;
self.span = span;
self.token = next;
self.expected_tokens.clear();
}
pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
F: FnOnce(&token::Token) -> R,
{
if dist == 0 {
return f(&self.token)
}
f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
Some(tree) => match tree {
TokenTree::Token(_, tok) => tok,
TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim),
},
None => token::CloseDelim(self.token_cursor.frame.delim),
})
}
fn look_ahead_span(&self, dist: usize) -> Span {
if dist == 0 {
return self.span
}
match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
Some(TokenTree::Token(span, _)) => span,
Some(TokenTree::Delimited(span, ..)) => span.entire(),
None => self.look_ahead_span(dist - 1),
}
}
pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
self.sess.span_diagnostic.struct_span_fatal(self.span, m)
}
pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
self.sess.span_diagnostic.struct_span_fatal(sp, m)
}
fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
err.span_err(sp, self.diagnostic())
}
fn bug(&self, m: &str) -> ! {
self.sess.span_diagnostic.span_bug(self.span, m)
}
fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
self.sess.span_diagnostic.span_err(sp, m)
}
fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
self.sess.span_diagnostic.struct_span_err(sp, m)
}
crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
self.sess.span_diagnostic.span_bug(sp, m)
}
fn cancel(&self, err: &mut DiagnosticBuilder<'_>) {
self.sess.span_diagnostic.cancel(err)
}
crate fn diagnostic(&self) -> &'a errors::Handler {
&self.sess.span_diagnostic
}
/// Is the current token one of the keywords that signals a bare function type?
fn token_is_bare_fn_keyword(&mut self) -> bool {
self.check_keyword(keywords::Fn) ||
self.check_keyword(keywords::Unsafe) ||
self.check_keyword(keywords::Extern)
}
/// Parses a `TyKind::BareFn` type.
fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
/*
[unsafe] [extern "ABI"] fn (S) -> T
^~~~^ ^~~~^ ^~^ ^
| | | |
| | | Return type
| | Argument types
| |
| ABI
Function Style
*/
let unsafety = self.parse_unsafety();
let abi = if self.eat_keyword(keywords::Extern) {
self.parse_opt_abi()?.unwrap_or(Abi::C)
} else {
Abi::Rust
};
self.expect_keyword(keywords::Fn)?;
let (inputs, variadic) = self.parse_fn_args(false, true)?;
let ret_ty = self.parse_ret_ty(false)?;
let decl = P(FnDecl {
inputs,
output: ret_ty,
variadic,
});
Ok(TyKind::BareFn(P(BareFnTy {
abi,
unsafety,
generic_params,
decl,
})))
}
/// Parses asyncness: `async` or nothing.
fn parse_asyncness(&mut self) -> IsAsync {
if self.eat_keyword(keywords::Async) {
IsAsync::Async {
closure_id: ast::DUMMY_NODE_ID,
return_impl_trait_id: ast::DUMMY_NODE_ID,
}
} else {
IsAsync::NotAsync
}
}
/// Parses unsafety: `unsafe` or nothing.
fn parse_unsafety(&mut self) -> Unsafety {
if self.eat_keyword(keywords::Unsafe) {
Unsafety::Unsafe
} else {
Unsafety::Normal
}
}
/// Parses the items in a trait declaration.
pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
maybe_whole!(self, NtTraitItem, |x| x);
let attrs = self.parse_outer_attributes()?;
let (mut item, tokens) = self.collect_tokens(|this| {
this.parse_trait_item_(at_end, attrs)
})?;
// See `parse_item` for why this clause is here.
if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
item.tokens = Some(tokens);
}
Ok(item)
}
fn parse_trait_item_(&mut self,
at_end: &mut bool,
mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
let lo = self.span;
let (name, node, generics) = if self.eat_keyword(keywords::Type) {
self.parse_trait_item_assoc_ty()?
} else if self.is_const_item() {
self.expect_keyword(keywords::Const)?;
let ident = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
let default = if self.eat(&token::Eq) {
let expr = self.parse_expr()?;
self.expect(&token::Semi)?;
Some(expr)
} else {
self.expect(&token::Semi)?;
None
};
(ident, TraitItemKind::Const(ty, default), ast::Generics::default())
} else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
// trait item macro.
(keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
} else {
let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
let ident = self.parse_ident()?;
let mut generics = self.parse_generics()?;
let d = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
// This is somewhat dubious; We don't want to allow
// argument names to be left off if there is a
// definition...
// We don't allow argument names to be left off in edition 2018.
p.parse_arg_general(p.span.rust_2018(), true)
})?;
generics.where_clause = self.parse_where_clause()?;
let sig = ast::MethodSig {
header: FnHeader {
unsafety,
constness,
abi,
asyncness,
},
decl: d,
};
let body = match self.token {
token::Semi => {
self.bump();
*at_end = true;
debug!("parse_trait_methods(): parsing required method");
None
}
token::OpenDelim(token::Brace) => {
debug!("parse_trait_methods(): parsing provided method");
*at_end = true;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(inner_attrs.iter().cloned());
Some(body)
}
token::Interpolated(ref nt) => {
match **nt {
token::NtBlock(..) => {
*at_end = true;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(inner_attrs.iter().cloned());
Some(body)
}
_ => {
let token_str = self.this_token_descr();
let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
token_str));
err.span_label(self.span, "expected `;` or `{`");
return Err(err);
}
}
}
_ => {
let token_str = self.this_token_descr();
let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
token_str));
err.span_label(self.span, "expected `;` or `{`");
return Err(err);
}
};
(ident, ast::TraitItemKind::Method(sig, body), generics)
};
Ok(TraitItem {
id: ast::DUMMY_NODE_ID,
ident: name,
attrs,
generics,
node,
span: lo.to(self.prev_span),
tokens: None,
})
}
/// Parses an optional return type `[ -> TY ]` in a function declaration.
fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
if self.eat(&token::RArrow) {
Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true)?))
} else {
Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
}
}
/// Parses a type.
pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
self.parse_ty_common(true, true)
}
/// Parses a type in restricted contexts where `+` is not permitted.
///
/// Example 1: `&'a TYPE`
/// `+` is prohibited to maintain operator priority (P(+) < P(&)).
/// Example 2: `value1 as TYPE + value2`
/// `+` is prohibited to avoid interactions with expression grammar.
fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
self.parse_ty_common(false, true)
}
fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool)
-> PResult<'a, P<Ty>> {
maybe_whole!(self, NtTy, |x| x);
let lo = self.span;
let mut impl_dyn_multi = false;
let node = if self.eat(&token::OpenDelim(token::Paren)) {
// `(TYPE)` is a parenthesized type.
// `(TYPE,)` is a tuple with a single field of type TYPE.
let mut ts = vec![];
let mut last_comma = false;
while self.token != token::CloseDelim(token::Paren) {
ts.push(self.parse_ty()?);
if self.eat(&token::Comma) {
last_comma = true;
} else {
last_comma = false;
break;
}
}
let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
self.expect(&token::CloseDelim(token::Paren))?;
if ts.len() == 1 && !last_comma {
let ty = ts.into_iter().nth(0).unwrap().into_inner();
let maybe_bounds = allow_plus && self.token.is_like_plus();
match ty.node {
// `(TY_BOUND_NOPAREN) + BOUND + ...`.
TyKind::Path(None, ref path) if maybe_bounds => {
self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
}
TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
let path = match bounds[0] {
GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
};
self.parse_remaining_bounds(Vec::new(), path, lo, true)?
}
// `(TYPE)`
_ => TyKind::Paren(P(ty))
}
} else {
TyKind::Tup(ts)
}
} else if self.eat(&token::Not) {
// Never type `!`
TyKind::Never
} else if self.eat(&token::BinOp(token::Star)) {
// Raw pointer
TyKind::Ptr(self.parse_ptr()?)
} else if self.eat(&token::OpenDelim(token::Bracket)) {
// Array or slice
let t = self.parse_ty()?;
// Parse optional `; EXPR` in `[TYPE; EXPR]`
let t = match self.maybe_parse_fixed_length_of_vec()? {
None => TyKind::Slice(t),
Some(length) => TyKind::Array(t, AnonConst {
id: ast::DUMMY_NODE_ID,
value: length,
}),
};
self.expect(&token::CloseDelim(token::Bracket))?;
t
} else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
// Reference
self.expect_and()?;
self.parse_borrowed_pointee()?
} else if self.eat_keyword_noexpect(keywords::Typeof) {
// `typeof(EXPR)`
// In order to not be ambiguous, the type must be surrounded by parens.
self.expect(&token::OpenDelim(token::Paren))?;
let e = AnonConst {
id: ast::DUMMY_NODE_ID,
value: self.parse_expr()?,
};
self.expect(&token::CloseDelim(token::Paren))?;
TyKind::Typeof(e)
} else if self.eat_keyword(keywords::Underscore) {
// A type to be inferred `_`
TyKind::Infer
} else if self.token_is_bare_fn_keyword() {
// Function pointer type
self.parse_ty_bare_fn(Vec::new())?
} else if self.check_keyword(keywords::For) {
// Function pointer type or bound list (trait object type) starting with a poly-trait.
// `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
// `for<'lt> Trait1<'lt> + Trait2 + 'a`
let lo = self.span;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
if self.token_is_bare_fn_keyword() {
self.parse_ty_bare_fn(lifetime_defs)?
} else {
let path = self.parse_path(PathStyle::Type)?;
let parse_plus = allow_plus && self.check_plus();
self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
}
} else if self.eat_keyword(keywords::Impl) {
// Always parse bounds greedily for better error recovery.
let bounds = self.parse_generic_bounds(None)?;
impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
} else if self.check_keyword(keywords::Dyn) &&
(self.span.rust_2018() ||
self.look_ahead(1, |t| t.can_begin_bound() &&
!can_continue_type_after_non_fn_ident(t))) {
self.bump(); // `dyn`
// Always parse bounds greedily for better error recovery.
let bounds = self.parse_generic_bounds(None)?;
impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
} else if self.check(&token::Question) ||
self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
// Bound list (trait object type)
TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
TraitObjectSyntax::None)
} else if self.eat_lt() {
// Qualified path
let (qself, path) = self.parse_qpath(PathStyle::Type)?;
TyKind::Path(Some(qself), path)
} else if self.token.is_path_start() {
// Simple path
let path = self.parse_path(PathStyle::Type)?;
if self.eat(&token::Not) {
// Macro invocation in type position
let (delim, tts) = self.expect_delimited_token_tree()?;
let node = Mac_ { path, tts, delim };
TyKind::Mac(respan(lo.to(self.prev_span), node))
} else {
// Just a type path or bound list (trait object type) starting with a trait.
// `Type`
// `Trait1 + Trait2 + 'a`
if allow_plus && self.check_plus() {
self.parse_remaining_bounds(Vec::new(), path, lo, true)?
} else {
TyKind::Path(None, path)
}
}
} else {
let msg = format!("expected type, found {}", self.this_token_descr());
return Err(self.fatal(&msg));
};
let span = lo.to(self.prev_span);
let ty = Ty { node, span, id: ast::DUMMY_NODE_ID };
// Try to recover from use of `+` with incorrect priority.
self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
let ty = self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)?;
Ok(P(ty))
}
fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
if parse_plus {
self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
bounds.append(&mut self.parse_generic_bounds(None)?);
}
Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
}
fn maybe_report_ambiguous_plus(&mut self, allow_plus: bool, impl_dyn_multi: bool, ty: &Ty) {
if !allow_plus && impl_dyn_multi {
let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
self.struct_span_err(ty.span, "ambiguous `+` in a type")
.span_suggestion(
ty.span,
"use parentheses to disambiguate",
sum_with_parens,
Applicability::MachineApplicable
).emit();
}
}
fn maybe_recover_from_bad_type_plus(&mut self, allow_plus: bool, ty: &Ty) -> PResult<'a, ()> {
// Do not add `+` to expected tokens.
if !allow_plus || !self.token.is_like_plus() {
return Ok(())
}
self.bump(); // `+`
let bounds = self.parse_generic_bounds(None)?;
let sum_span = ty.span.to(self.prev_span);
let mut err = struct_span_err!(self.sess.span_diagnostic, sum_span, E0178,
"expected a path on the left-hand side of `+`, not `{}`", pprust::ty_to_string(ty));
match ty.node {
TyKind::Rptr(ref lifetime, ref mut_ty) => {
let sum_with_parens = pprust::to_string(|s| {
use crate::print::pprust::PrintState;
s.s.word("&")?;
s.print_opt_lifetime(lifetime)?;
s.print_mutability(mut_ty.mutbl)?;
s.popen()?;
s.print_type(&mut_ty.ty)?;
s.print_type_bounds(" +", &bounds)?;
s.pclose()
});
err.span_suggestion(
sum_span,
"try adding parentheses",
sum_with_parens,
Applicability::MachineApplicable
);
}
TyKind::Ptr(..) | TyKind::BareFn(..) => {
err.span_label(sum_span, "perhaps you forgot parentheses?");
}
_ => {
err.span_label(sum_span, "expected a path");
},
}
err.emit();
Ok(())
}
// Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: T, allow_recovery: bool)
-> PResult<'a, T> {
// Do not add `::` to expected tokens.
if !allow_recovery || self.token != token::ModSep {
return Ok(base);
}
let ty = match base.to_ty() {
Some(ty) => ty,
None => return Ok(base),
};
self.bump(); // `::`
let mut segments = Vec::new();
self.parse_path_segments(&mut segments, T::PATH_STYLE, true)?;
let span = ty.span.to(self.prev_span);
let path_span = span.to(span); // use an empty path since `position` == 0
let recovered = base.to_recovered(
Some(QSelf { ty, path_span, position: 0 }),
ast::Path { segments, span },
);
self.diagnostic()
.struct_span_err(span, "missing angle brackets in associated item path")
.span_suggestion( // this is a best-effort recovery
span, "try", recovered.to_string(), Applicability::MaybeIncorrect
).emit();
Ok(recovered)
}
fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
let mutbl = self.parse_mutability();
let ty = self.parse_ty_no_plus()?;
return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
}
fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
let mutbl = if self.eat_keyword(keywords::Mut) {
Mutability::Mutable
} else if self.eat_keyword(keywords::Const) {
Mutability::Immutable
} else {
let span = self.prev_span;
let msg = "expected mut or const in raw pointer type";
self.struct_span_err(span, msg)
.span_label(span, msg)
.help("use `*mut T` or `*const T` as appropriate")
.emit();
Mutability::Immutable
};
let t = self.parse_ty_no_plus()?;
Ok(MutTy { ty: t, mutbl: mutbl })
}
fn is_named_argument(&mut self) -> bool {
let offset = match self.token {
token::Interpolated(ref nt) => match **nt {
token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
_ => 0,
}
token::BinOp(token::And) | token::AndAnd => 1,
_ if self.token.is_keyword(keywords::Mut) => 1,
_ => 0,
};
self.look_ahead(offset, |t| t.is_ident()) &&
self.look_ahead(offset + 1, |t| t == &token::Colon)
}
/// Skips unexpected attributes and doc comments in this position and emits an appropriate
/// error.
fn eat_incorrect_doc_comment(&mut self, applied_to: &str) {
if let token::DocComment(_) = self.token {
let mut err = self.diagnostic().struct_span_err(
self.span,
&format!("documentation comments cannot be applied to {}", applied_to),
);
err.span_label(self.span, "doc comments are not allowed here");
err.emit();
self.bump();
} else if self.token == token::Pound && self.look_ahead(1, |t| {
*t == token::OpenDelim(token::Bracket)
}) {
let lo = self.span;
// Skip every token until next possible arg.
while self.token != token::CloseDelim(token::Bracket) {
self.bump();
}
let sp = lo.to(self.span);
self.bump();
let mut err = self.diagnostic().struct_span_err(
sp,
&format!("attributes cannot be applied to {}", applied_to),
);
err.span_label(sp, "attributes are not allowed here");
err.emit();
}
}
/// This version of parse arg doesn't necessarily require identifier names.
fn parse_arg_general(&mut self, require_name: bool, is_trait_item: bool) -> PResult<'a, Arg> {
maybe_whole!(self, NtArg, |x| x);
if let Ok(Some(_)) = self.parse_self_arg() {
let mut err = self.struct_span_err(self.prev_span,
"unexpected `self` argument in function");
err.span_label(self.prev_span,
"`self` is only valid as the first argument of an associated function");
return Err(err);
}
let (pat, ty) = if require_name || self.is_named_argument() {
debug!("parse_arg_general parse_pat (require_name:{})",
require_name);
self.eat_incorrect_doc_comment("method arguments");
let pat = self.parse_pat(Some("argument name"))?;
if let Err(mut err) = self.expect(&token::Colon) {
// If we find a pattern followed by an identifier, it could be an (incorrect)
// C-style parameter declaration.
if self.check_ident() && self.look_ahead(1, |t| {
*t == token::Comma || *t == token::CloseDelim(token::Paren)
}) {
let ident = self.parse_ident().unwrap();
let span = pat.span.with_hi(ident.span.hi());
err.span_suggestion(
span,
"declare the type after the parameter binding",
String::from("<identifier>: <type>"),
Applicability::HasPlaceholders,
);
} else if require_name && is_trait_item {
if let PatKind::Ident(_, ident, _) = pat.node {
err.span_suggestion(
pat.span,
"explicitly ignore parameter",
format!("_: {}", ident),
Applicability::MachineApplicable,
);
}
err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)");
}
return Err(err);
}
self.eat_incorrect_doc_comment("a method argument's type");
(pat, self.parse_ty()?)
} else {
debug!("parse_arg_general ident_to_pat");
let parser_snapshot_before_ty = self.clone();
self.eat_incorrect_doc_comment("a method argument's type");
let mut ty = self.parse_ty();
if ty.is_ok() && self.token != token::Comma &&
self.token != token::CloseDelim(token::Paren) {
// This wasn't actually a type, but a pattern looking like a type,
// so we are going to rollback and re-parse for recovery.
ty = self.unexpected();
}
match ty {
Ok(ty) => {
let ident = Ident::new(keywords::Invalid.name(), self.prev_span);
let pat = P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Ident(
BindingMode::ByValue(Mutability::Immutable), ident, None),
span: ty.span,
});
(pat, ty)
}
Err(mut err) => {
// Recover from attempting to parse the argument as a type without pattern.
err.cancel();
mem::replace(self, parser_snapshot_before_ty);
let pat = self.parse_pat(Some("argument name"))?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
let mut err = self.diagnostic().struct_span_err_with_code(
pat.span,
"patterns aren't allowed in methods without bodies",
DiagnosticId::Error("E0642".into()),
);
err.span_suggestion_short(
pat.span,
"give this argument a name or use an underscore to ignore it",
"_".to_owned(),
Applicability::MachineApplicable,
);
err.emit();
// Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
let pat = P(Pat {
node: PatKind::Wild,
span: pat.span,
id: ast::DUMMY_NODE_ID
});
(pat, ty)
}
}
};
Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID })
}
/// Parses a single function argument.
crate fn parse_arg(&mut self) -> PResult<'a, Arg> {
self.parse_arg_general(true, false)
}
/// Parses an argument in a lambda header (e.g., `|arg, arg|`).
fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
let pat = self.parse_pat(Some("argument name"))?;
let t = if self.eat(&token::Colon) {
self.parse_ty()?
} else {
P(Ty {
id: ast::DUMMY_NODE_ID,
node: TyKind::Infer,
span: self.prev_span,
})
};
Ok(Arg {
ty: t,
pat,
id: ast::DUMMY_NODE_ID
})
}
fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
if self.eat(&token::Semi) {
Ok(Some(self.parse_expr()?))
} else {
Ok(None)
}
}
/// Matches `token_lit = LIT_INTEGER | ...`.
fn parse_lit_token(&mut self) -> PResult<'a, LitKind> {
let out = match self.token {
token::Interpolated(ref nt) => match **nt {
token::NtExpr(ref v) | token::NtLiteral(ref v) => match v.node {
ExprKind::Lit(ref lit) => { lit.node.clone() }
_ => { return self.unexpected_last(&self.token); }
},
_ => { return self.unexpected_last(&self.token); }
},
token::Literal(lit, suf) => {
let diag = Some((self.span, &self.sess.span_diagnostic));
let (suffix_illegal, result) = parse::lit_token(lit, suf, diag);
if suffix_illegal {
let sp = self.span;
self.expect_no_suffix(sp, lit.literal_name(), suf)
}
result.unwrap()
}
token::Dot if self.look_ahead(1, |t| match t {
token::Literal(parse::token::Lit::Integer(_) , _) => true,
_ => false,
}) => { // recover from `let x = .4;`
let lo = self.span;
self.bump();
if let token::Literal(
parse::token::Lit::Integer(val),
suffix,
) = self.token {
let suffix = suffix.and_then(|s| {
let s = s.as_str().get();
if ["f32", "f64"].contains(&s) {
Some(s)
} else {
None
}
}).unwrap_or("");
self.bump();
let sp = lo.to(self.prev_span);
let mut err = self.diagnostic()
.struct_span_err(sp, "float literals must have an integer part");
err.span_suggestion(
sp,
"must have an integer part",
format!("0.{}{}", val, suffix),
Applicability::MachineApplicable,
);
err.emit();
return Ok(match suffix {
"f32" => ast::LitKind::Float(val, ast::FloatTy::F32),
"f64" => ast::LitKind::Float(val, ast::FloatTy::F64),
_ => ast::LitKind::FloatUnsuffixed(val),
});
} else {
unreachable!();
};
}
_ => { return self.unexpected_last(&self.token); }
};
self.bump();
Ok(out)
}
/// Matches `lit = true | false | token_lit`.
crate fn parse_lit(&mut self) -> PResult<'a, Lit> {
let lo = self.span;
let lit = if self.eat_keyword(keywords::True) {
LitKind::Bool(true)
} else if self.eat_keyword(keywords::False) {
LitKind::Bool(false)
} else {
let lit = self.parse_lit_token()?;
lit
};
Ok(source_map::Spanned { node: lit, span: lo.to(self.prev_span) })
}
/// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
maybe_whole_expr!(self);
let minus_lo = self.span;
let minus_present = self.eat(&token::BinOp(token::Minus));
let lo = self.span;
let literal = self.parse_lit()?;
let hi = self.prev_span;
let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
if minus_present {
let minus_hi = self.prev_span;
let unary = self.mk_unary(UnOp::Neg, expr);
Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
} else {
Ok(expr)
}
}
fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
match self.token {
token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
let span = self.span;
self.bump();
Ok(Ident::new(ident.name, span))
}
_ => self.parse_ident(),
}
}
fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
match self.token {
token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
let span = self.span;
self.bump();
Ok(Ident::new(ident.name, span))
}
_ => self.parse_ident(),
}
}
/// Parses a qualified path.
/// Assumes that the leading `<` has been parsed already.
///
/// `qualified_path = <type [as trait_ref]>::path`
///
/// # Examples
/// `<T>::default`
/// `<T as U>::a`
/// `<T as U>::F::a<S>` (without disambiguator)
/// `<T as U>::F::a::<S>` (with disambiguator)
fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
let lo = self.prev_span;
let ty = self.parse_ty()?;
// `path` will contain the prefix of the path up to the `>`,
// if any (e.g., `U` in the `<T as U>::*` examples
// above). `path_span` has the span of that path, or an empty
// span in the case of something like `<T>::Bar`.
let (mut path, path_span);
if self.eat_keyword(keywords::As) {
let path_lo = self.span;
path = self.parse_path(PathStyle::Type)?;
path_span = path_lo.to(self.prev_span);
} else {
path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
path_span = self.span.to(self.span);
}
// See doc comment for `unmatched_angle_bracket_count`.
self.expect(&token::Gt)?;
if self.unmatched_angle_bracket_count > 0 {
self.unmatched_angle_bracket_count -= 1;
debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
}
self.expect(&token::ModSep)?;
let qself = QSelf { ty, path_span, position: path.segments.len() };
self.parse_path_segments(&mut path.segments, style, true)?;
Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
}
/// Parses simple paths.
///
/// `path = [::] segment+`
/// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
///
/// # Examples
/// `a::b::C<D>` (without disambiguator)
/// `a::b::C::<D>` (with disambiguator)
/// `Fn(Args)` (without disambiguator)
/// `Fn::(Args)` (with disambiguator)
pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
self.parse_path_common(style, true)
}
crate fn parse_path_common(&mut self, style: PathStyle, enable_warning: bool)
-> PResult<'a, ast::Path> {
maybe_whole!(self, NtPath, |path| {
if style == PathStyle::Mod &&
path.segments.iter().any(|segment| segment.args.is_some()) {
self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
}
path
});
let lo = self.meta_var_span.unwrap_or(self.span);
let mut segments = Vec::new();
let mod_sep_ctxt = self.span.ctxt();
if self.eat(&token::ModSep) {
segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
}
self.parse_path_segments(&mut segments, style, enable_warning)?;
Ok(ast::Path { segments, span: lo.to(self.prev_span) })
}
/// Like `parse_path`, but also supports parsing `Word` meta items into paths for
/// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
/// attributes.
pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
let meta_ident = match self.token {
token::Interpolated(ref nt) => match **nt {
token::NtMeta(ref meta) => match meta.node {
ast::MetaItemKind::Word => Some(meta.ident.clone()),
_ => None,
},
_ => None,
},
_ => None,
};
if let Some(path) = meta_ident {
self.bump();
return Ok(path);
}
self.parse_path(style)
}
fn parse_path_segments(&mut self,
segments: &mut Vec<PathSegment>,
style: PathStyle,
enable_warning: bool)
-> PResult<'a, ()> {
loop {
let segment = self.parse_path_segment(style, enable_warning)?;
if style == PathStyle::Expr {
// In order to check for trailing angle brackets, we must have finished
// recursing (`parse_path_segment` can indirectly call this function),
// that is, the next token must be the highlighted part of the below example:
//
// `Foo::<Bar as Baz<T>>::Qux`
// ^ here
//
// As opposed to the below highlight (if we had only finished the first
// recursion):
//
// `Foo::<Bar as Baz<T>>::Qux`
// ^ here
//
// `PathStyle::Expr` is only provided at the root invocation and never in
// `parse_path_segment` to recurse and therefore can be checked to maintain
// this invariant.
self.check_trailing_angle_brackets(&segment, token::ModSep);
}
segments.push(segment);
if self.is_import_coupler() || !self.eat(&token::ModSep) {
return Ok(());
}
}
}
fn parse_path_segment(&mut self, style: PathStyle, enable_warning: bool)
-> PResult<'a, PathSegment> {
let ident = self.parse_path_segment_ident()?;
let is_args_start = |token: &token::Token| match *token {
token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren) => true,
_ => false,
};
let check_args_start = |this: &mut Self| {
this.expected_tokens.extend_from_slice(
&[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
);
is_args_start(&this.token)
};
Ok(if style == PathStyle::Type && check_args_start(self) ||
style != PathStyle::Mod && self.check(&token::ModSep)
&& self.look_ahead(1, |t| is_args_start(t)) {
// Generic arguments are found - `<`, `(`, `::<` or `::(`.
if self.eat(&token::ModSep) && style == PathStyle::Type && enable_warning {
self.diagnostic().struct_span_warn(self.prev_span, "unnecessary path disambiguator")
.span_label(self.prev_span, "try removing `::`").emit();
}
let lo = self.span;
// We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
// it isn't, then we reset the unmatched angle bracket count as we're about to start
// parsing a new path.
if style == PathStyle::Expr {
self.unmatched_angle_bracket_count = 0;
self.max_angle_bracket_count = 0;
}
let args = if self.eat_lt() {
// `<'a, T, A = U>`
let (args, bindings) =
self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
self.expect_gt()?;
let span = lo.to(self.prev_span);
AngleBracketedArgs { args, bindings, span }.into()
} else {
// `(T, U) -> R`
self.bump(); // `(`
let (inputs, recovered) = self.parse_seq_to_before_tokens(
&[&token::CloseDelim(token::Paren)],
SeqSep::trailing_allowed(token::Comma),
TokenExpectType::Expect,
|p| p.parse_ty())?;
if !recovered {
self.bump(); // `)`
}
let span = lo.to(self.prev_span);
let output = if self.eat(&token::RArrow) {
Some(self.parse_ty_common(false, false)?)
} else {
None
};
ParenthesizedArgs { inputs, output, span }.into()
};
PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
} else {
// Generic arguments are not found.
PathSegment::from_ident(ident)
})
}
crate fn check_lifetime(&mut self) -> bool {
self.expected_tokens.push(TokenType::Lifetime);
self.token.is_lifetime()
}
/// Parses a single lifetime `'a` or panics.
crate fn expect_lifetime(&mut self) -> Lifetime {
if let Some(ident) = self.token.lifetime() {
let span = self.span;
self.bump();
Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
} else {
self.span_bug(self.span, "not a lifetime")
}
}
fn eat_label(&mut self) -> Option<Label> {
if let Some(ident) = self.token.lifetime() {
let span = self.span;
self.bump();
Some(Label { ident: Ident::new(ident.name, span) })
} else {
None
}
}
/// Parses mutability (`mut` or nothing).
fn parse_mutability(&mut self) -> Mutability {
if self.eat_keyword(keywords::Mut) {
Mutability::Mutable
} else {
Mutability::Immutable
}
}
fn parse_field_name(&mut self) -> PResult<'a, Ident> {
if let token::Literal(token::Integer(name), None) = self.token {
self.bump();
Ok(Ident::new(name, self.prev_span))
} else {
self.parse_ident_common(false)
}
}
/// Parse ident (COLON expr)?
fn parse_field(&mut self) -> PResult<'a, Field> {
let attrs = self.parse_outer_attributes()?;
let lo = self.span;
// Check if a colon exists one ahead. This means we're parsing a fieldname.
let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
t == &token::Colon || t == &token::Eq
}) {
let fieldname = self.parse_field_name()?;
// Check for an equals token. This means the source incorrectly attempts to
// initialize a field with an eq rather than a colon.
if self.token == token::Eq {
self.diagnostic()
.struct_span_err(self.span, "expected `:`, found `=`")
.span_suggestion(
fieldname.span.shrink_to_hi().to(self.span),
"replace equals symbol with a colon",
":".to_string(),
Applicability::MachineApplicable,
)
.emit();
}
self.bump(); // `:`
(fieldname, self.parse_expr()?, false)
} else {
let fieldname = self.parse_ident_common(false)?;
// Mimic `x: x` for the `x` field shorthand.
let path = ast::Path::from_ident(fieldname);
let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
(fieldname, expr, true)
};
Ok(ast::Field {
ident: fieldname,
span: lo.to(expr.span),
expr,
is_shorthand,
attrs: attrs.into(),
})
}
fn mk_expr(&mut self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
}
fn mk_unary(&mut self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
ExprKind::Unary(unop, expr)
}
fn mk_binary(&mut self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
ExprKind::Binary(binop, lhs, rhs)
}
fn mk_call(&mut self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
ExprKind::Call(f, args)
}
fn mk_index(&mut self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
ExprKind::Index(expr, idx)
}
fn mk_range(&mut self,
start: Option<P<Expr>>,
end: Option<P<Expr>>,
limits: RangeLimits)
-> PResult<'a, ast::ExprKind> {
if end.is_none() && limits == RangeLimits::Closed {
Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
} else {
Ok(ExprKind::Range(start, end, limits))
}
}
fn mk_assign_op(&mut self, binop: ast::BinOp,
lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
ExprKind::AssignOp(binop, lhs, rhs)
}
pub fn mk_mac_expr(&mut self, span: Span, m: Mac_, attrs: ThinVec<Attribute>) -> P<Expr> {
P(Expr {
id: ast::DUMMY_NODE_ID,
node: ExprKind::Mac(source_map::Spanned {node: m, span: span}),
span,
attrs,
})
}
fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
let delim = match self.token {
token::OpenDelim(delim) => delim,
_ => {
let msg = "expected open delimiter";
let mut err = self.fatal(msg);
err.span_label(self.span, msg);
return Err(err)
}
};
let tts = match self.parse_token_tree() {
TokenTree::Delimited(_, _, tts) => tts,
_ => unreachable!(),
};
let delim = match delim {
token::Paren => MacDelimiter::Parenthesis,
token::Bracket => MacDelimiter::Bracket,
token::Brace => MacDelimiter::Brace,
token::NoDelim => self.bug("unexpected no delimiter"),
};
Ok((delim, tts.into()))
}
/// At the bottom (top?) of the precedence hierarchy,
/// Parses things like parenthesized exprs, macros, `return`, etc.
///
/// N.B., this does not parse outer attributes, and is private because it only works
/// correctly if called from `parse_dot_or_call_expr()`.
fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
maybe_whole_expr!(self);
// Outer attributes are already parsed and will be
// added to the return value after the fact.
//
// Therefore, prevent sub-parser from parsing
// attributes by giving them a empty "already parsed" list.
let mut attrs = ThinVec::new();
let lo = self.span;
let mut hi = self.span;
let ex: ExprKind;
// Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
match self.token {
token::OpenDelim(token::Paren) => {
self.bump();
attrs.extend(self.parse_inner_attributes()?);
// (e) is parenthesized e
// (e,) is a tuple with only one field, e
let mut es = vec![];
let mut trailing_comma = false;
let mut recovered = false;
while self.token != token::CloseDelim(token::Paren) {
es.push(self.parse_expr()?);
recovered = self.expect_one_of(
&[],
&[token::Comma, token::CloseDelim(token::Paren)],
)?;
if self.eat(&token::Comma) {
trailing_comma = true;
} else {
trailing_comma = false;
break;
}
}
if !recovered {
self.bump();
}
hi = self.prev_span;
ex = if es.len() == 1 && !trailing_comma {
ExprKind::Paren(es.into_iter().nth(0).unwrap())
} else {
ExprKind::Tup(es)
};
}
token::OpenDelim(token::Brace) => {
return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
}
token::BinOp(token::Or) | token::OrOr => {
return self.parse_lambda_expr(attrs);
}
token::OpenDelim(token::Bracket) => {
self.bump();
attrs.extend(self.parse_inner_attributes()?);
if self.eat(&token::CloseDelim(token::Bracket)) {
// Empty vector.
ex = ExprKind::Array(Vec::new());
} else {
// Nonempty vector.
let first_expr = self.parse_expr()?;
if self.eat(&token::Semi) {
// Repeating array syntax: [ 0; 512 ]
let count = AnonConst {
id: ast::DUMMY_NODE_ID,
value: self.parse_expr()?,
};
self.expect(&token::CloseDelim(token::Bracket))?;
ex = ExprKind::Repeat(first_expr, count);
} else if self.eat(&token::Comma) {
// Vector with two or more elements.
let remaining_exprs = self.parse_seq_to_end(
&token::CloseDelim(token::Bracket),
SeqSep::trailing_allowed(token::Comma),
|p| Ok(p.parse_expr()?)
)?;
let mut exprs = vec![first_expr];
exprs.extend(remaining_exprs);
ex = ExprKind::Array(exprs);
} else {
// Vector with one element.
self.expect(&token::CloseDelim(token::Bracket))?;
ex = ExprKind::Array(vec![first_expr]);
}
}
hi = self.prev_span;
}
_ => {
if self.eat_lt() {
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
hi = path.span;
return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
}
if self.span.rust_2018() && self.check_keyword(keywords::Async)
{
if self.is_async_block() { // check for `async {` and `async move {`
return self.parse_async_block(attrs);
} else {
return self.parse_lambda_expr(attrs);
}
}
if self.check_keyword(keywords::Move) || self.check_keyword(keywords::Static) {
return self.parse_lambda_expr(attrs);
}
if self.eat_keyword(keywords::If) {
return self.parse_if_expr(attrs);
}
if self.eat_keyword(keywords::For) {
let lo = self.prev_span;
return self.parse_for_expr(None, lo, attrs);
}
if self.eat_keyword(keywords::While) {
let lo = self.prev_span;
return self.parse_while_expr(None, lo, attrs);
}
if let Some(label) = self.eat_label() {
let lo = label.ident.span;
self.expect(&token::Colon)?;
if self.eat_keyword(keywords::While) {
return self.parse_while_expr(Some(label), lo, attrs)
}
if self.eat_keyword(keywords::For) {
return self.parse_for_expr(Some(label), lo, attrs)
}
if self.eat_keyword(keywords::Loop) {
return self.parse_loop_expr(Some(label), lo, attrs)
}
if self.token == token::OpenDelim(token::Brace) {
return self.parse_block_expr(Some(label),
lo,
BlockCheckMode::Default,
attrs);
}
let msg = "expected `while`, `for`, `loop` or `{` after a label";
let mut err = self.fatal(msg);
err.span_label(self.span, msg);
return Err(err);
}
if self.eat_keyword(keywords::Loop) {
let lo = self.prev_span;
return self.parse_loop_expr(None, lo, attrs);
}
if self.eat_keyword(keywords::Continue) {
let label = self.eat_label();
let ex = ExprKind::Continue(label);
let hi = self.prev_span;
return Ok(self.mk_expr(lo.to(hi), ex, attrs));
}
if self.eat_keyword(keywords::Match) {
let match_sp = self.prev_span;
return self.parse_match_expr(attrs).map_err(|mut err| {
err.span_label(match_sp, "while parsing this match expression");
err
});
}
if self.eat_keyword(keywords::Unsafe) {
return self.parse_block_expr(
None,
lo,
BlockCheckMode::Unsafe(ast::UserProvided),
attrs);
}
if self.is_do_catch_block() {
let mut db = self.fatal("found removed `do catch` syntax");
db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
return Err(db);
}
if self.is_try_block() {
let lo = self.span;
assert!(self.eat_keyword(keywords::Try));
return self.parse_try_block(lo, attrs);
}
if self.eat_keyword(keywords::Return) {
if self.token.can_begin_expr() {
let e = self.parse_expr()?;
hi = e.span;
ex = ExprKind::Ret(Some(e));
} else {
ex = ExprKind::Ret(None);
}
} else if self.eat_keyword(keywords::Break) {
let label = self.eat_label();
let e = if self.token.can_begin_expr()
&& !(self.token == token::OpenDelim(token::Brace)
&& self.restrictions.contains(
Restrictions::NO_STRUCT_LITERAL)) {
Some(self.parse_expr()?)
} else {
None
};
ex = ExprKind::Break(label, e);
hi = self.prev_span;
} else if self.eat_keyword(keywords::Yield) {
if self.token.can_begin_expr() {
let e = self.parse_expr()?;
hi = e.span;
ex = ExprKind::Yield(Some(e));
} else {
ex = ExprKind::Yield(None);
}
} else if self.token.is_keyword(keywords::Let) {
// Catch this syntax error here, instead of in `parse_ident`, so
// that we can explicitly mention that let is not to be used as an expression
let mut db = self.fatal("expected expression, found statement (`let`)");
db.span_label(self.span, "expected expression");
db.note("variable declaration using `let` is a statement");
return Err(db);
} else if self.token.is_path_start() {
let pth = self.parse_path(PathStyle::Expr)?;
// `!`, as an operator, is prefix, so we know this isn't that
if self.eat(&token::Not) {
// MACRO INVOCATION expression
let (delim, tts) = self.expect_delimited_token_tree()?;
let hi = self.prev_span;
let node = Mac_ { path: pth, tts, delim };
return Ok(self.mk_mac_expr(lo.to(hi), node, attrs))
}
if self.check(&token::OpenDelim(token::Brace)) {
// This is a struct literal, unless we're prohibited
// from parsing struct literals here.
let prohibited = self.restrictions.contains(
Restrictions::NO_STRUCT_LITERAL
);
if !prohibited {
return self.parse_struct_expr(lo, pth, attrs);
}
}
hi = pth.span;
ex = ExprKind::Path(None, pth);
} else {
if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
// Don't complain about bare semicolons after unclosed braces
// recovery in order to keep the error count down. Fixing the
// delimiters will possibly also fix the bare semicolon found in
// expression context. For example, silence the following error:
// ```
// error: expected expression, found `;`
// --> file.rs:2:13
// |
// 2 | foo(bar(;
// | ^ expected expression
// ```
self.bump();
return Ok(self.mk_expr(self.span, ExprKind::Err, ThinVec::new()));
}
match self.parse_literal_maybe_minus() {
Ok(expr) => {
hi = expr.span;
ex = expr.node.clone();
}
Err(mut err) => {
self.cancel(&mut err);
let msg = format!("expected expression, found {}",
self.this_token_descr());
let mut err = self.fatal(&msg);
err.span_label(self.span, "expected expression");
return Err(err);
}
}
}
}
}
let expr = Expr { node: ex, span: lo.to(hi), id: ast::DUMMY_NODE_ID, attrs };
let expr = self.maybe_recover_from_bad_qpath(expr, true)?;
return Ok(P(expr));
}
fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
let struct_sp = lo.to(self.prev_span);
self.bump();
let mut fields = Vec::new();
let mut base = None;
attrs.extend(self.parse_inner_attributes()?);
while self.token != token::CloseDelim(token::Brace) {
if self.eat(&token::DotDot) {
let exp_span = self.prev_span;
match self.parse_expr() {
Ok(e) => {
base = Some(e);
}
Err(mut e) => {
e.emit();
self.recover_stmt();
}
}
if self.token == token::Comma {
let mut err = self.sess.span_diagnostic.mut_span_err(
exp_span.to(self.prev_span),
"cannot use a comma after the base struct",
);
err.span_suggestion_short(
self.span,
"remove this comma",
String::new(),
Applicability::MachineApplicable
);
err.note("the base struct must always be the last field");
err.emit();
self.recover_stmt();
}
break;
}
let mut recovery_field = None;
if let token::Ident(ident, _) = self.token {
if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
// Use in case of error after field-looking code: `S { foo: () with a }`
let mut ident = ident.clone();
ident.span = self.span;
recovery_field = Some(ast::Field {
ident,
span: self.span,
expr: self.mk_expr(self.span, ExprKind::Err, ThinVec::new()),
is_shorthand: false,
attrs: ThinVec::new(),
});
}
}
let mut parsed_field = None;
match self.parse_field() {
Ok(f) => parsed_field = Some(f),
Err(mut e) => {
e.span_label(struct_sp, "while parsing this struct");
e.emit();
// If the next token is a comma, then try to parse
// what comes next as additional fields, rather than
// bailing out until next `}`.
if self.token != token::Comma {
self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
if self.token != token::Comma {
break;
}
}
}
}
match self.expect_one_of(&[token::Comma],
&[token::CloseDelim(token::Brace)]) {
Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
// only include the field if there's no parse error for the field name
fields.push(f);
}
Err(mut e) => {
if let Some(f) = recovery_field {
fields.push(f);
}
e.span_label(struct_sp, "while parsing this struct");
e.emit();
self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
self.eat(&token::Comma);
}
}
}
let span = lo.to(self.span);
self.expect(&token::CloseDelim(token::Brace))?;
return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
}
fn parse_or_use_outer_attributes(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, ThinVec<Attribute>> {
if let Some(attrs) = already_parsed_attrs {
Ok(attrs)
} else {
self.parse_outer_attributes().map(|a| a.into())
}
}
/// Parses a block or unsafe block.
fn parse_block_expr(&mut self, opt_label: Option<Label>,
lo: Span, blk_mode: BlockCheckMode,
outer_attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
self.expect(&token::OpenDelim(token::Brace))?;
let mut attrs = outer_attrs;
attrs.extend(self.parse_inner_attributes()?);
let blk = self.parse_block_tail(lo, blk_mode)?;
return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
}
/// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
fn parse_dot_or_call_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
let b = self.parse_bottom_expr();
let (span, b) = self.interpolated_or_expr_span(b)?;
self.parse_dot_or_call_expr_with(b, span, attrs)
}
fn parse_dot_or_call_expr_with(&mut self,
e0: P<Expr>,
lo: Span,
mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
// Stitch the list of outer attributes onto the return value.
// A little bit ugly, but the best way given the current code
// structure
self.parse_dot_or_call_expr_with_(e0, lo)
.map(|expr|
expr.map(|mut expr| {
attrs.extend::<Vec<_>>(expr.attrs.into());
expr.attrs = attrs;
match expr.node {
ExprKind::If(..) | ExprKind::IfLet(..) => {
if !expr.attrs.is_empty() {
// Just point to the first attribute in there...
let span = expr.attrs[0].span;
self.span_err(span,
"attributes are not yet allowed on `if` \
expressions");
}
}
_ => {}
}
expr
})
)
}
// Assuming we have just parsed `.`, continue parsing into an expression.
fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
let segment = self.parse_path_segment(PathStyle::Expr, true)?;
self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
Ok(match self.token {
token::OpenDelim(token::Paren) => {
// Method call `expr.f()`
let mut args = self.parse_unspanned_seq(
&token::OpenDelim(token::Paren),
&token::CloseDelim(token::Paren),
SeqSep::trailing_allowed(token::Comma),
|p| Ok(p.parse_expr()?)
)?;
args.insert(0, self_arg);
let span = lo.to(self.prev_span);
self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
}
_ => {
// Field access `expr.f`
if let Some(args) = segment.args {
self.span_err(args.span(),
"field expressions may not have generic arguments");
}
let span = lo.to(self.prev_span);
self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
}
})
}
/// This function checks if there are trailing angle brackets and produces
/// a diagnostic to suggest removing them.
///
/// ```ignore (diagnostic)
/// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
/// ^^ help: remove extra angle brackets
/// ```
fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: token::Token) {
// This function is intended to be invoked after parsing a path segment where there are two
// cases:
//
// 1. A specific token is expected after the path segment.
// eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
// `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
// 2. No specific token is expected after the path segment.
// eg. `x.foo` (field access)
//
// This function is called after parsing `.foo` and before parsing the token `end` (if
// present). This includes any angle bracket arguments, such as `.foo::<u32>` or
// `Foo::<Bar>`.
// We only care about trailing angle brackets if we previously parsed angle bracket
// arguments. This helps stop us incorrectly suggesting that extra angle brackets be
// removed in this case:
//
// `x.foo >> (3)` (where `x.foo` is a `u32` for example)
//
// This case is particularly tricky as we won't notice it just looking at the tokens -
// it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
// have already been parsed):
//
// `x.foo::<u32>>>(3)`
let parsed_angle_bracket_args = segment.args
.as_ref()
.map(|args| args.is_angle_bracketed())
.unwrap_or(false);
debug!(
"check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
parsed_angle_bracket_args,
);
if !parsed_angle_bracket_args {
return;
}
// Keep the span at the start so we can highlight the sequence of `>` characters to be
// removed.
let lo = self.span;
// We need to look-ahead to see if we have `>` characters without moving the cursor forward
// (since we might have the field access case and the characters we're eating are
// actual operators and not trailing characters - ie `x.foo >> 3`).
let mut position = 0;
// We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
// many of each (so we can correctly pluralize our error messages) and continue to
// advance.
let mut number_of_shr = 0;
let mut number_of_gt = 0;
while self.look_ahead(position, |t| {
trace!("check_trailing_angle_brackets: t={:?}", t);
if *t == token::BinOp(token::BinOpToken::Shr) {
number_of_shr += 1;
true
} else if *t == token::Gt {
number_of_gt += 1;
true
} else {
false
}
}) {
position += 1;
}
// If we didn't find any trailing `>` characters, then we have nothing to error about.
debug!(
"check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
number_of_gt, number_of_shr,
);
if number_of_gt < 1 && number_of_shr < 1 {
return;
}
// Finally, double check that we have our end token as otherwise this is the
// second case.
if self.look_ahead(position, |t| {
trace!("check_trailing_angle_brackets: t={:?}", t);
*t == end
}) {
// Eat from where we started until the end token so that parsing can continue
// as if we didn't have those extra angle brackets.
self.eat_to_tokens(&[&end]);
let span = lo.until(self.span);
let plural = number_of_gt > 1 || number_of_shr >= 1;
self.diagnostic()
.struct_span_err(
span,
&format!("unmatched angle bracket{}", if plural { "s" } else { "" }),
)
.span_suggestion(
span,
&format!("remove extra angle bracket{}", if plural { "s" } else { "" }),
String::new(),
Applicability::MachineApplicable,
)
.emit();
}
}
fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
let mut e = e0;
let mut hi;
loop {
// expr?
while self.eat(&token::Question) {
let hi = self.prev_span;
e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
}
// expr.f
if self.eat(&token::Dot) {
match self.token {
token::Ident(..) => {
e = self.parse_dot_suffix(e, lo)?;
}
token::Literal(token::Integer(name), _) => {
let span = self.span;
self.bump();
let field = ExprKind::Field(e, Ident::new(name, span));
e = self.mk_expr(lo.to(span), field, ThinVec::new());
}
token::Literal(token::Float(n), _suf) => {
self.bump();
let fstr = n.as_str();
let mut err = self.diagnostic()
.struct_span_err(self.prev_span, &format!("unexpected token: `{}`", n));
err.span_label(self.prev_span, "unexpected token");
if fstr.chars().all(|x| "0123456789.".contains(x)) {
let float = match fstr.parse::<f64>().ok() {
Some(f) => f,
None => continue,
};
let sugg = pprust::to_string(|s| {
use crate::print::pprust::PrintState;
s.popen()?;
s.print_expr(&e)?;
s.s.word( ".")?;
s.print_usize(float.trunc() as usize)?;
s.pclose()?;
s.s.word(".")?;
s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
});
err.span_suggestion(
lo.to(self.prev_span),
"try parenthesizing the first index",
sugg,
Applicability::MachineApplicable
);
}
return Err(err);
}
_ => {
// FIXME Could factor this out into non_fatal_unexpected or something.
let actual = self.this_token_to_string();
self.span_err(self.span, &format!("unexpected token: `{}`", actual));
}
}
continue;
}
if self.expr_is_complete(&e) { break; }
match self.token {
// expr(...)
token::OpenDelim(token::Paren) => {
let es = self.parse_unspanned_seq(
&token::OpenDelim(token::Paren),
&token::CloseDelim(token::Paren),
SeqSep::trailing_allowed(token::Comma),
|p| Ok(p.parse_expr()?)
)?;
hi = self.prev_span;
let nd = self.mk_call(e, es);
e = self.mk_expr(lo.to(hi), nd, ThinVec::new());
}
// expr[...]
// Could be either an index expression or a slicing expression.
token::OpenDelim(token::Bracket) => {
self.bump();
let ix = self.parse_expr()?;
hi = self.span;
self.expect(&token::CloseDelim(token::Bracket))?;
let index = self.mk_index(e, ix);
e = self.mk_expr(lo.to(hi), index, ThinVec::new())
}
_ => return Ok(e)
}
}
return Ok(e);
}
crate fn process_potential_macro_variable(&mut self) {
let (token, span) = match self.token {
token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
self.look_ahead(1, |t| t.is_ident()) => {
self.bump();
let name = match self.token {
token::Ident(ident, _) => ident,
_ => unreachable!()
};
let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
err.span_label(self.span, "unknown macro variable");
err.emit();
self.bump();
return
}
token::Interpolated(ref nt) => {
self.meta_var_span = Some(self.span);
// Interpolated identifier and lifetime tokens are replaced with usual identifier
// and lifetime tokens, so the former are never encountered during normal parsing.
match **nt {
token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span),
token::NtLifetime(ident) => (token::Lifetime(ident), ident.span),
_ => return,
}
}
_ => return,
};
self.token = token;
self.span = span;
}
/// Parses a single token tree from the input.
crate fn parse_token_tree(&mut self) -> TokenTree {
match self.token {
token::OpenDelim(..) => {
let frame = mem::replace(&mut self.token_cursor.frame,
self.token_cursor.stack.pop().unwrap());
self.span = frame.span.entire();
self.bump();
TokenTree::Delimited(
frame.span,
frame.delim,
frame.tree_cursor.stream.into(),
)
},
token::CloseDelim(_) | token::Eof => unreachable!(),
_ => {
let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span);
self.bump();
TokenTree::Token(span, token)
}
}
}
// parse a stream of tokens into a list of TokenTree's,
// up to EOF.
pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
let mut tts = Vec::new();
while self.token != token::Eof {
tts.push(self.parse_token_tree());
}
Ok(tts)
}
pub fn parse_tokens(&mut self) -> TokenStream {
let mut result = Vec::new();
loop {
match self.token {
token::Eof | token::CloseDelim(..) => break,
_ => result.push(self.parse_token_tree().into()),
}
}
TokenStream::new(result)
}
/// Parse a prefix-unary-operator expr
fn parse_prefix_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
let lo = self.span;
// Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
let (hi, ex) = match self.token {
token::Not => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Not, e))
}
// Suggest `!` for bitwise negation when encountering a `~`
token::Tilde => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
let span_of_tilde = lo;
let mut err = self.diagnostic()
.struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
err.span_suggestion_short(
span_of_tilde,
"use `!` to perform bitwise negation",
"!".to_owned(),
Applicability::MachineApplicable
);
err.emit();
(lo.to(span), self.mk_unary(UnOp::Not, e))
}
token::BinOp(token::Minus) => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Neg, e))
}
token::BinOp(token::Star) => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Deref, e))
}
token::BinOp(token::And) | token::AndAnd => {
self.expect_and()?;
let m = self.parse_mutability();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), ExprKind::AddrOf(m, e))
}
token::Ident(..) if self.token.is_keyword(keywords::In) => {
self.bump();
let place = self.parse_expr_res(
Restrictions::NO_STRUCT_LITERAL,
None,
)?;
let blk = self.parse_block()?;
let span = blk.span;
let blk_expr = self.mk_expr(span, ExprKind::Block(blk, None), ThinVec::new());
(lo.to(span), ExprKind::ObsoleteInPlace(place, blk_expr))
}
token::Ident(..) if self.token.is_keyword(keywords::Box) => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), ExprKind::Box(e))
}
token::Ident(..) if self.token.is_ident_named("not") => {
// `not` is just an ordinary identifier in Rust-the-language,
// but as `rustc`-the-compiler, we can issue clever diagnostics
// for confused users who really want to say `!`
let token_cannot_continue_expr = |t: &token::Token| match *t {
// These tokens can start an expression after `!`, but
// can't continue an expression after an ident
token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
token::Literal(..) | token::Pound => true,
token::Interpolated(ref nt) => match **nt {
token::NtIdent(..) | token::NtExpr(..) |
token::NtBlock(..) | token::NtPath(..) => true,
_ => false,
},
_ => false
};
let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
if cannot_continue_expr {
self.bump();
// Emit the error ...
let mut err = self.diagnostic()
.struct_span_err(self.span,
&format!("unexpected {} after identifier",
self.this_token_descr()));
// span the `not` plus trailing whitespace to avoid
// trailing whitespace after the `!` in our suggestion
let to_replace = self.sess.source_map()
.span_until_non_whitespace(lo.to(self.span));
err.span_suggestion_short(
to_replace,
"use `!` to perform logical negation",
"!".to_owned(),
Applicability::MachineApplicable
);
err.emit();
// —and recover! (just as if we were in the block
// for the `token::Not` arm)
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Not, e))
} else {
return self.parse_dot_or_call_expr(Some(attrs));
}
}
_ => { return self.parse_dot_or_call_expr(Some(attrs)); }
};
return Ok(self.mk_expr(lo.to(hi), ex, attrs));
}
/// Parses an associative expression.
///
/// This parses an expression accounting for associativity and precedence of the operators in
/// the expression.
#[inline]
fn parse_assoc_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
self.parse_assoc_expr_with(0, already_parsed_attrs.into())
}
/// Parses an associative expression with operators of at least `min_prec` precedence.
fn parse_assoc_expr_with(&mut self,
min_prec: usize,
lhs: LhsExpr)
-> PResult<'a, P<Expr>> {
let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
expr
} else {
let attrs = match lhs {
LhsExpr::AttributesParsed(attrs) => Some(attrs),
_ => None,
};
if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
return self.parse_prefix_range_expr(attrs);
} else {
self.parse_prefix_expr(attrs)?
}
};
if self.expr_is_complete(&lhs) {
// Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
return Ok(lhs);
}
self.expected_tokens.push(TokenType::Operator);
while let Some(op) = AssocOp::from_token(&self.token) {
// Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
// it refers to. Interpolated identifiers are unwrapped early and never show up here
// as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
// it as "interpolated", it doesn't change the answer for non-interpolated idents.
let lhs_span = match (self.prev_token_kind, &lhs.node) {
(PrevTokenKind::Interpolated, _) => self.prev_span,
(PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
if path.segments.len() == 1 => self.prev_span,
_ => lhs.span,
};
let cur_op_span = self.span;
let restrictions = if op.is_assign_like() {
self.restrictions & Restrictions::NO_STRUCT_LITERAL
} else {
self.restrictions
};
if op.precedence() < min_prec {
break;
}
// Check for deprecated `...` syntax
if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
self.err_dotdotdot_syntax(self.span);
}
self.bump();
if op.is_comparison() {
self.check_no_chained_comparison(&lhs, &op);
}
// Special cases:
if op == AssocOp::As {
lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
continue
} else if op == AssocOp::Colon {
lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
Ok(lhs) => lhs,
Err(mut err) => {
err.span_label(self.span,
"expecting a type here because of type ascription");
let cm = self.sess.source_map();
let cur_pos = cm.lookup_char_pos(self.span.lo());
let op_pos = cm.lookup_char_pos(cur_op_span.hi());
if cur_pos.line != op_pos.line {
err.span_suggestion(
cur_op_span,
"try using a semicolon",
";".to_string(),
Applicability::MaybeIncorrect // speculative
);
}
return Err(err);
}
};
continue
} else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
// If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
// generalise it to the Fixity::None code.
//
// We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
// two variants are handled with `parse_prefix_range_expr` call above.
let rhs = if self.is_at_start_of_range_notation_rhs() {
Some(self.parse_assoc_expr_with(op.precedence() + 1,
LhsExpr::NotYetParsed)?)
} else {
None
};
let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
x.span
} else {
cur_op_span
});
let limits = if op == AssocOp::DotDot {
RangeLimits::HalfOpen
} else {
RangeLimits::Closed
};
let r = self.mk_range(Some(lhs), rhs, limits)?;
lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
break
}
let rhs = match op.fixity() {
Fixity::Right => self.with_res(
restrictions - Restrictions::STMT_EXPR,
|this| {
this.parse_assoc_expr_with(op.precedence(),
LhsExpr::NotYetParsed)
}),
Fixity::Left => self.with_res(
restrictions - Restrictions::STMT_EXPR,
|this| {
this.parse_assoc_expr_with(op.precedence() + 1,
LhsExpr::NotYetParsed)
}),
// We currently have no non-associative operators that are not handled above by
// the special cases. The code is here only for future convenience.
Fixity::None => self.with_res(
restrictions - Restrictions::STMT_EXPR,
|this| {
this.parse_assoc_expr_with(op.precedence() + 1,
LhsExpr::NotYetParsed)
}),
}?;
// Make sure that the span of the parent node is larger than the span of lhs and rhs,
// including the attributes.
let lhs_span = lhs
.attrs
.iter()
.filter(|a| a.style == AttrStyle::Outer)
.next()
.map_or(lhs_span, |a| a.span);
let span = lhs_span.to(rhs.span);
lhs = match op {
AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
AssocOp::Greater | AssocOp::GreaterEqual => {
let ast_op = op.to_ast_binop().unwrap();
let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
self.mk_expr(span, binary, ThinVec::new())
}
AssocOp::Assign =>
self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
AssocOp::ObsoleteInPlace =>
self.mk_expr(span, ExprKind::ObsoleteInPlace(lhs, rhs), ThinVec::new()),
AssocOp::AssignOp(k) => {
let aop = match k {
token::Plus => BinOpKind::Add,
token::Minus => BinOpKind::Sub,
token::Star => BinOpKind::Mul,
token::Slash => BinOpKind::Div,
token::Percent => BinOpKind::Rem,
token::Caret => BinOpKind::BitXor,
token::And => BinOpKind::BitAnd,
token::Or => BinOpKind::BitOr,
token::Shl => BinOpKind::Shl,
token::Shr => BinOpKind::Shr,
};
let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
self.mk_expr(span, aopexpr, ThinVec::new())
}
AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
self.bug("AssocOp should have been handled by special case")
}
};
if op.fixity() == Fixity::None { break }
}
Ok(lhs)
}
fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
-> PResult<'a, P<Expr>> {
let mk_expr = |this: &mut Self, rhs: P<Ty>| {
this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
};
// Save the state of the parser before parsing type normally, in case there is a
// LessThan comparison after this cast.
let parser_snapshot_before_type = self.clone();
match self.parse_ty_no_plus() {
Ok(rhs) => {
Ok(mk_expr(self, rhs))
}
Err(mut type_err) => {
// Rewind to before attempting to parse the type with generics, to recover
// from situations like `x as usize < y` in which we first tried to parse
// `usize < y` as a type with generic arguments.
let parser_snapshot_after_type = self.clone();
mem::replace(self, parser_snapshot_before_type);
match self.parse_path(PathStyle::Expr) {
Ok(path) => {
let (op_noun, op_verb) = match self.token {
token::Lt => ("comparison", "comparing"),
token::BinOp(token::Shl) => ("shift", "shifting"),
_ => {
// We can end up here even without `<` being the next token, for
// example because `parse_ty_no_plus` returns `Err` on keywords,
// but `parse_path` returns `Ok` on them due to error recovery.
// Return original error and parser state.
mem::replace(self, parser_snapshot_after_type);
return Err(type_err);
}
};
// Successfully parsed the type path leaving a `<` yet to parse.
type_err.cancel();
// Report non-fatal diagnostics, keep `x as usize` as an expression
// in AST and continue parsing.
let msg = format!("`<` is interpreted as a start of generic \
arguments for `{}`, not a {}", path, op_noun);
let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
"interpreted as generic arguments");
err.span_label(self.span, format!("not interpreted as {}", op_noun));
let expr = mk_expr(self, P(Ty {
span: path.span,
node: TyKind::Path(None, path),
id: ast::DUMMY_NODE_ID
}));
let expr_str = self.sess.source_map().span_to_snippet(expr.span)
.unwrap_or_else(|_| pprust::expr_to_string(&expr));
err.span_suggestion(
expr.span,
&format!("try {} the cast value", op_verb),
format!("({})", expr_str),
Applicability::MachineApplicable
);
err.emit();
Ok(expr)
}
Err(mut path_err) => {
// Couldn't parse as a path, return original error and parser state.
path_err.cancel();
mem::replace(self, parser_snapshot_after_type);
Err(type_err)
}
}
}
}
}
/// Produce an error if comparison operators are chained (RFC #558).
/// We only need to check lhs, not rhs, because all comparison ops
/// have same precedence and are left-associative
fn check_no_chained_comparison(&mut self, lhs: &Expr, outer_op: &AssocOp) {
debug_assert!(outer_op.is_comparison(),
"check_no_chained_comparison: {:?} is not comparison",
outer_op);
match lhs.node {
ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
// respan to include both operators
let op_span = op.span.to(self.span);
let mut err = self.diagnostic().struct_span_err(op_span,
"chained comparison operators require parentheses");
if op.node == BinOpKind::Lt &&
*outer_op == AssocOp::Less || // Include `<` to provide this recommendation
*outer_op == AssocOp::Greater // even in a case like the following:
{ // Foo<Bar<Baz<Qux, ()>>>
err.help(
"use `::<...>` instead of `<...>` if you meant to specify type arguments");
err.help("or use `(...)` if you meant to specify fn arguments");
}
err.emit();
}
_ => {}
}
}
/// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
fn parse_prefix_range_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
// Check for deprecated `...` syntax
if self.token == token::DotDotDot {
self.err_dotdotdot_syntax(self.span);
}
debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
"parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
self.token);
let tok = self.token.clone();
let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
let lo = self.span;
let mut hi = self.span;
self.bump();
let opt_end = if self.is_at_start_of_range_notation_rhs() {
// RHS must be parsed with more associativity than the dots.
let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
Some(self.parse_assoc_expr_with(next_prec,
LhsExpr::NotYetParsed)
.map(|x|{
hi = x.span;
x
})?)
} else {
None
};
let limits = if tok == token::DotDot {
RangeLimits::HalfOpen
} else {
RangeLimits::Closed
};
let r = self.mk_range(None, opt_end, limits)?;
Ok(self.mk_expr(lo.to(hi), r, attrs))
}
fn is_at_start_of_range_notation_rhs(&self) -> bool {
if self.token.can_begin_expr() {
// parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
if self.token == token::OpenDelim(token::Brace) {
return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
}
true
} else {
false
}
}
/// Parses an `if` or `if let` expression (`if` token already eaten).
fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
if self.check_keyword(keywords::Let) {
return self.parse_if_let_expr(attrs);
}
let lo = self.prev_span;
let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
// Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
// verify that the last statement is either an implicit return (no `;`) or an explicit
// return. This won't catch blocks with an explicit `return`, but that would be caught by
// the dead code lint.
if self.eat_keyword(keywords::Else) || !cond.returns() {
let sp = self.sess.source_map().next_point(lo);
let mut err = self.diagnostic()
.struct_span_err(sp, "missing condition for `if` statemement");
err.span_label(sp, "expected if condition here");
return Err(err)
}
let not_block = self.token != token::OpenDelim(token::Brace);
let thn = self.parse_block().map_err(|mut err| {
if not_block {
err.span_label(lo, "this `if` statement has a condition, but no block");
}
err
})?;
let mut els: Option<P<Expr>> = None;
let mut hi = thn.span;
if self.eat_keyword(keywords::Else) {
let elexpr = self.parse_else_expr()?;
hi = elexpr.span;
els = Some(elexpr);
}
Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
}
/// Parses an `if let` expression (`if` token already eaten).
fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
let lo = self.prev_span;
self.expect_keyword(keywords::Let)?;
let pats = self.parse_pats()?;
self.expect(&token::Eq)?;
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let thn = self.parse_block()?;
let (hi, els) = if self.eat_keyword(keywords::Else) {
let expr = self.parse_else_expr()?;
(expr.span, Some(expr))
} else {
(thn.span, None)
};
Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
}
/// Parses `move |args| expr`.
fn parse_lambda_expr(&mut self,
attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>>
{
let lo = self.span;
let movability = if self.eat_keyword(keywords::Static) {
Movability::Static
} else {
Movability::Movable
};
let asyncness = if self.span.rust_2018() {
self.parse_asyncness()
} else {
IsAsync::NotAsync
};
let capture_clause = if self.eat_keyword(keywords::Move) {
CaptureBy::Value
} else {
CaptureBy::Ref
};
let decl = self.parse_fn_block_decl()?;
let decl_hi = self.prev_span;
let body = match decl.output {
FunctionRetTy::Default(_) => {
let restrictions = self.restrictions - Restrictions::STMT_EXPR;
self.parse_expr_res(restrictions, None)?
},
_ => {
// If an explicit return type is given, require a
// block to appear (RFC 968).
let body_lo = self.span;
self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
}
};
Ok(self.mk_expr(
lo.to(body.span),
ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
attrs))
}
// `else` token already eaten
fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
if self.eat_keyword(keywords::If) {
return self.parse_if_expr(ThinVec::new());
} else {
let blk = self.parse_block()?;
return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
}
}
/// Parse a 'for' .. 'in' expression ('for' token already eaten)
fn parse_for_expr(&mut self, opt_label: Option<Label>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
// Parse: `for <src_pat> in <src_expr> <src_loop_block>`
let pat = self.parse_top_level_pat()?;
if !self.eat_keyword(keywords::In) {
let in_span = self.prev_span.between(self.span);
let mut err = self.sess.span_diagnostic
.struct_span_err(in_span, "missing `in` in `for` loop");
err.span_suggestion_short(
in_span, "try adding `in` here", " in ".into(),
// has been misleading, at least in the past (closed Issue #48492)
Applicability::MaybeIncorrect
);
err.emit();
}
let in_span = self.prev_span;
if self.eat_keyword(keywords::In) {
// a common typo: `for _ in in bar {}`
let mut err = self.sess.span_diagnostic.struct_span_err(
self.prev_span,
"expected iterable, found keyword `in`",
);
err.span_suggestion_short(
in_span.until(self.prev_span),
"remove the duplicated `in`",
String::new(),
Applicability::MachineApplicable,
);
err.note("if you meant to use emplacement syntax, it is obsolete (for now, anyway)");
err.note("for more information on the status of emplacement syntax, see <\
https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>");
err.emit();
}
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let hi = self.prev_span;
Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
}
/// Parses a `while` or `while let` expression (`while` token already eaten).
fn parse_while_expr(&mut self, opt_label: Option<Label>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
if self.token.is_keyword(keywords::Let) {
return self.parse_while_let_expr(opt_label, span_lo, attrs);
}
let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let span = span_lo.to(body.span);
return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
}
/// Parses a `while let` expression (`while` token already eaten).
fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
self.expect_keyword(keywords::Let)?;
let pats = self.parse_pats()?;
self.expect(&token::Eq)?;
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let span = span_lo.to(body.span);
return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
}
// parse `loop {...}`, `loop` token already eaten
fn parse_loop_expr(&mut self, opt_label: Option<Label>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let span = span_lo.to(body.span);
Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
}
/// Parses an `async move {...}` expression.
pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>>
{
let span_lo = self.span;
self.expect_keyword(keywords::Async)?;
let capture_clause = if self.eat_keyword(keywords::Move) {
CaptureBy::Value
} else {
CaptureBy::Ref
};
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
Ok(self.mk_expr(
span_lo.to(body.span),
ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
}
/// Parses a `try {...}` expression (`try` token already eaten).
fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>>
{
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
}
// `match` token already eaten
fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
let match_span = self.prev_span;
let lo = self.prev_span;
let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
None)?;
if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
if self.token == token::Token::Semi {
e.span_suggestion_short(
match_span,
"try removing this `match`",
String::new(),
Applicability::MaybeIncorrect // speculative
);
}
return Err(e)
}
attrs.extend(self.parse_inner_attributes()?);
let mut arms: Vec<Arm> = Vec::new();
while self.token != token::CloseDelim(token::Brace) {
match self.parse_arm() {
Ok(arm) => arms.push(arm),
Err(mut e) => {
// Recover by skipping to the end of the block.
e.emit();
self.recover_stmt();
let span = lo.to(self.span);
if self.token == token::CloseDelim(token::Brace) {
self.bump();
}
return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
}
}
}
let hi = self.span;
self.bump();
return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
}
crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
maybe_whole!(self, NtArm, |x| x);
let attrs = self.parse_outer_attributes()?;
let pats = self.parse_pats()?;
let guard = if self.eat_keyword(keywords::If) {
Some(Guard::If(self.parse_expr()?))
} else {
None
};
let arrow_span = self.span;
self.expect(&token::FatArrow)?;
let arm_start_span = self.span;
let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
.map_err(|mut err| {
err.span_label(arrow_span, "while parsing the `match` arm starting here");
err
})?;
let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
&& self.token != token::CloseDelim(token::Brace);
if require_comma {
let cm = self.sess.source_map();
self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
.map_err(|mut err| {
match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
(Ok(ref expr_lines), Ok(ref arm_start_lines))
if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
&& expr_lines.lines.len() == 2
&& self.token == token::FatArrow => {
// We check whether there's any trailing code in the parse span,
// if there isn't, we very likely have the following:
//
// X | &Y => "y"
// | -- - missing comma
// | |
// | arrow_span
// X | &X => "x"
// | - ^^ self.span
// | |
// | parsed until here as `"y" & X`
err.span_suggestion_short(
cm.next_point(arm_start_span),
"missing a comma here to end this `match` arm",
",".to_owned(),
Applicability::MachineApplicable
);
}
_ => {
err.span_label(arrow_span,
"while parsing the `match` arm starting here");
}
}
err
})?;
} else {
self.eat(&token::Comma);
}
Ok(ast::Arm {
attrs,
pats,
guard,
body: expr,
})
}
/// Parses an expression.
#[inline]
pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
self.parse_expr_res(Restrictions::empty(), None)
}
/// Evaluates the closure with restrictions in place.
///
/// Afters the closure is evaluated, restrictions are reset.
fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
where F: FnOnce(&mut Self) -> T
{
let old = self.restrictions;
self.restrictions = r;
let r = f(self);
self.restrictions = old;
return r;
}
/// Parses an expression, subject to the given restrictions.
#[inline]
fn parse_expr_res(&mut self, r: Restrictions,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
}
/// Parses the RHS of a local variable declaration (e.g., '= 14;').
fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
if self.eat(&token::Eq) {
Ok(Some(self.parse_expr()?))
} else if skip_eq {
Ok(Some(self.parse_expr()?))
} else {
Ok(None)
}
}
/// Parses patterns, separated by '|' s.
fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
// Allow a '|' before the pats (RFC 1925 + RFC 2530)
self.eat(&token::BinOp(token::Or));
let mut pats = Vec::new();
loop {
pats.push(self.parse_top_level_pat()?);
if self.token == token::OrOr {
let mut err = self.struct_span_err(self.span,
"unexpected token `||` after pattern");
err.span_suggestion(
self.span,
"use a single `|` to specify multiple patterns",
"|".to_owned(),
Applicability::MachineApplicable
);
err.emit();
self.bump();
} else if self.eat(&token::BinOp(token::Or)) {
// This is a No-op. Continue the loop to parse the next
// pattern.
} else {
return Ok(pats);
}
};
}
// Parses a parenthesized list of patterns like
// `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
// - a vector of the patterns that were parsed
// - an option indicating the index of the `..` element
// - a boolean indicating whether a trailing comma was present.
// Trailing commas are significant because (p) and (p,) are different patterns.
fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
self.expect(&token::OpenDelim(token::Paren))?;
let result = self.parse_pat_list()?;
self.expect(&token::CloseDelim(token::Paren))?;
Ok(result)
}
fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
let mut fields = Vec::new();
let mut ddpos = None;
let mut trailing_comma = false;
loop {
if self.eat(&token::DotDot) {
if ddpos.is_none() {
ddpos = Some(fields.len());
} else {
// Emit a friendly error, ignore `..` and continue parsing
self.struct_span_err(
self.prev_span,
"`..` can only be used once per tuple or tuple struct pattern",
)
.span_label(self.prev_span, "can only be used once per pattern")
.emit();
}
} else if !self.check(&token::CloseDelim(token::Paren)) {
fields.push(self.parse_pat(None)?);
} else {
break
}
trailing_comma = self.eat(&token::Comma);
if !trailing_comma {
break
}
}
if ddpos == Some(fields.len()) && trailing_comma {
// `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
let msg = "trailing comma is not permitted after `..`";
self.struct_span_err(self.prev_span, msg)
.span_label(self.prev_span, msg)
.emit();
}
Ok((fields, ddpos, trailing_comma))
}
fn parse_pat_vec_elements(
&mut self,
) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
let mut before = Vec::new();
let mut slice = None;
let mut after = Vec::new();
let mut first = true;
let mut before_slice = true;
while self.token != token::CloseDelim(token::Bracket) {
if first {
first = false;
} else {
self.expect(&token::Comma)?;
if self.token == token::CloseDelim(token::Bracket)
&& (before_slice || !after.is_empty()) {
break
}
}
if before_slice {
if self.eat(&token::DotDot) {
if self.check(&token::Comma) ||
self.check(&token::CloseDelim(token::Bracket)) {
slice = Some(P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Wild,
span: self.prev_span,
}));
before_slice = false;
}
continue
}
}
let subpat = self.parse_pat(None)?;
if before_slice && self.eat(&token::DotDot) {
slice = Some(subpat);
before_slice = false;
} else if before_slice {
before.push(subpat);
} else {
after.push(subpat);
}
}
Ok((before, slice, after))
}
fn parse_pat_field(
&mut self,
lo: Span,
attrs: Vec<Attribute>
) -> PResult<'a, source_map::Spanned<ast::FieldPat>> {
// Check if a colon exists one ahead. This means we're parsing a fieldname.
let hi;
let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
// Parsing a pattern of the form "fieldname: pat"
let fieldname = self.parse_field_name()?;
self.bump();
let pat = self.parse_pat(None)?;
hi = pat.span;
(pat, fieldname, false)
} else {
// Parsing a pattern of the form "(box) (ref) (mut) fieldname"
let is_box = self.eat_keyword(keywords::Box);
let boxed_span = self.span;
let is_ref = self.eat_keyword(keywords::Ref);
let is_mut = self.eat_keyword(keywords::Mut);
let fieldname = self.parse_ident()?;
hi = self.prev_span;
let bind_type = match (is_ref, is_mut) {
(true, true) => BindingMode::ByRef(Mutability::Mutable),
(true, false) => BindingMode::ByRef(Mutability::Immutable),
(false, true) => BindingMode::ByValue(Mutability::Mutable),
(false, false) => BindingMode::ByValue(Mutability::Immutable),
};
let fieldpat = P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Ident(bind_type, fieldname, None),
span: boxed_span.to(hi),
});
let subpat = if is_box {
P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Box(fieldpat),
span: lo.to(hi),
})
} else {
fieldpat
};
(subpat, fieldname, true)
};
Ok(source_map::Spanned {
span: lo.to(hi),
node: ast::FieldPat {
ident: fieldname,
pat: subpat,
is_shorthand,
attrs: attrs.into(),
}
})
}
/// Parses the fields of a struct-like pattern.
fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> {
let mut fields = Vec::new();
let mut etc = false;
let mut ate_comma = true;
let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
let mut etc_span = None;
while self.token != token::CloseDelim(token::Brace) {
let attrs = self.parse_outer_attributes()?;
let lo = self.span;
// check that a comma comes after every field
if !ate_comma {
let err = self.struct_span_err(self.prev_span, "expected `,`");
if let Some(mut delayed) = delayed_err {
delayed.emit();
}
return Err(err);
}
ate_comma = false;
if self.check(&token::DotDot) || self.token == token::DotDotDot {
etc = true;
let mut etc_sp = self.span;
if self.token == token::DotDotDot { // Issue #46718
// Accept `...` as if it were `..` to avoid further errors
let mut err = self.struct_span_err(self.span,
"expected field pattern, found `...`");
err.span_suggestion(
self.span,
"to omit remaining fields, use one fewer `.`",
"..".to_owned(),
Applicability::MachineApplicable
);
err.emit();
}
self.bump(); // `..` || `...`
if self.token == token::CloseDelim(token::Brace) {
etc_span = Some(etc_sp);
break;
}
let token_str = self.this_token_descr();
let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
err.span_label(self.span, "expected `}`");
let mut comma_sp = None;
if self.token == token::Comma { // Issue #49257
etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span));
err.span_label(etc_sp,
"`..` must be at the end and cannot have a trailing comma");
comma_sp = Some(self.span);
self.bump();
ate_comma = true;
}
etc_span = Some(etc_sp.until(self.span));
if self.token == token::CloseDelim(token::Brace) {
// If the struct looks otherwise well formed, recover and continue.
if let Some(sp) = comma_sp {
err.span_suggestion_short(
sp,
"remove this comma",
String::new(),
Applicability::MachineApplicable,
);
}
err.emit();
break;
} else if self.token.is_ident() && ate_comma {
// Accept fields coming after `..,`.
// This way we avoid "pattern missing fields" errors afterwards.
// We delay this error until the end in order to have a span for a
// suggested fix.
if let Some(mut delayed_err) = delayed_err {
delayed_err.emit();
return Err(err);
} else {
delayed_err = Some(err);
}
} else {
if let Some(mut err) = delayed_err {
err.emit();
}
return Err(err);
}
}
fields.push(match self.parse_pat_field(lo, attrs) {
Ok(field) => field,
Err(err) => {
if let Some(mut delayed_err) = delayed_err {
delayed_err.emit();
}
return Err(err);
}
});
ate_comma = self.eat(&token::Comma);
}
if let Some(mut err) = delayed_err {
if let Some(etc_span) = etc_span {
err.multipart_suggestion(
"move the `..` to the end of the field list",
vec![
(etc_span, String::new()),
(self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
],
Applicability::MachineApplicable,
);
}
err.emit();
}
return Ok((fields, etc));
}
fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
if self.token.is_path_start() {
let lo = self.span;
let (qself, path) = if self.eat_lt() {
// Parse a qualified path
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
(Some(qself), path)
} else {
// Parse an unqualified path
(None, self.parse_path(PathStyle::Expr)?)
};
let hi = self.prev_span;
Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
} else {
self.parse_literal_maybe_minus()
}
}
// helper function to decide whether to parse as ident binding or to try to do
// something more complex like range patterns
fn parse_as_ident(&mut self) -> bool {
self.look_ahead(1, |t| match *t {
token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
// ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
// range pattern branch
token::DotDot => None,
_ => Some(true),
}).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
token::Comma | token::CloseDelim(token::Bracket) => true,
_ => false,
}))
}
/// A wrapper around `parse_pat` with some special error handling for the
/// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
/// to subpatterns within such).
fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
let pat = self.parse_pat(None)?;
if self.token == token::Comma {
// An unexpected comma after a top-level pattern is a clue that the
// user (perhaps more accustomed to some other language) forgot the
// parentheses in what should have been a tuple pattern; return a
// suggestion-enhanced error here rather than choking on the comma
// later.
let comma_span = self.span;
self.bump();
if let Err(mut err) = self.parse_pat_list() {
// We didn't expect this to work anyway; we just wanted
// to advance to the end of the comma-sequence so we know
// the span to suggest parenthesizing
err.cancel();
}
let seq_span = pat.span.to(self.prev_span);
let mut err = self.struct_span_err(comma_span,
"unexpected `,` in pattern");
if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
err.span_suggestion(
seq_span,
"try adding parentheses to match on a tuple..",
format!("({})", seq_snippet),
Applicability::MachineApplicable
).span_suggestion(
seq_span,
"..or a vertical bar to match on multiple alternatives",
format!("{}", seq_snippet.replace(",", " |")),
Applicability::MachineApplicable
);
}
return Err(err);
}
Ok(pat)
}
/// Parses a pattern.
pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
self.parse_pat_with_range_pat(true, expected)
}
/// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
/// allowed).
fn parse_pat_with_range_pat(
&mut self,
allow_range_pat: bool,
expected: Option<&'static str>,
) -> PResult<'a, P<Pat>> {
maybe_whole!(self, NtPat, |x| x);
let lo = self.span;
let pat;
match self.token {
token::BinOp(token::And) | token::AndAnd => {
// Parse &pat / &mut pat
self.expect_and()?;
let mutbl = self.parse_mutability();
if let token::Lifetime(ident) = self.token {
let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
ident));
err.span_label(self.span, "unexpected lifetime");
return Err(err);
}
let subpat = self.parse_pat_with_range_pat(false, expected)?;
pat = PatKind::Ref(subpat, mutbl);
}
token::OpenDelim(token::Paren) => {
// Parse (pat,pat,pat,...) as tuple pattern
let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
PatKind::Paren(fields.into_iter().nth(0).unwrap())
} else {
PatKind::Tuple(fields, ddpos)
};
}
token::OpenDelim(token::Bracket) => {
// Parse [pat,pat,...] as slice pattern
self.bump();
let (before, slice, after) = self.parse_pat_vec_elements()?;
self.expect(&token::CloseDelim(token::Bracket))?;
pat = PatKind::Slice(before, slice, after);
}
// At this point, token != &, &&, (, [
_ => if self.eat_keyword(keywords::Underscore) {
// Parse _
pat = PatKind::Wild;
} else if self.eat_keyword(keywords::Mut) {
// Parse mut ident @ pat / mut ref ident @ pat
let mutref_span = self.prev_span.to(self.span);
let binding_mode = if self.eat_keyword(keywords::Ref) {
self.diagnostic()
.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
.span_suggestion(
mutref_span,
"try switching the order",
"ref mut".into(),
Applicability::MachineApplicable
).emit();
BindingMode::ByRef(Mutability::Mutable)
} else {
BindingMode::ByValue(Mutability::Mutable)
};
pat = self.parse_pat_ident(binding_mode)?;
} else if self.eat_keyword(keywords::Ref) {
// Parse ref ident @ pat / ref mut ident @ pat
let mutbl = self.parse_mutability();
pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
} else if self.eat_keyword(keywords::Box) {
// Parse box pat
let subpat = self.parse_pat_with_range_pat(false, None)?;
pat = PatKind::Box(subpat);
} else if self.token.is_ident() && !self.token.is_reserved_ident() &&
self.parse_as_ident() {
// Parse ident @ pat
// This can give false positives and parse nullary enums,
// they are dealt with later in resolve
let binding_mode = BindingMode::ByValue(Mutability::Immutable);
pat = self.parse_pat_ident(binding_mode)?;
} else if self.token.is_path_start() {
// Parse pattern starting with a path
let (qself, path) = if self.eat_lt() {
// Parse a qualified path
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
(Some(qself), path)
} else {
// Parse an unqualified path
(None, self.parse_path(PathStyle::Expr)?)
};
match self.token {
token::Not if qself.is_none() => {
// Parse macro invocation
self.bump();
let (delim, tts) = self.expect_delimited_token_tree()?;
let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
pat = PatKind::Mac(mac);
}
token::DotDotDot | token::DotDotEq | token::DotDot => {
let end_kind = match self.token {
token::DotDot => RangeEnd::Excluded,
token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
_ => panic!("can only parse `..`/`...`/`..=` for ranges \
(checked above)"),
};
let op_span = self.span;
// Parse range
let span = lo.to(self.prev_span);
let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
self.bump();
let end = self.parse_pat_range_end()?;
let op = Spanned { span: op_span, node: end_kind };
pat = PatKind::Range(begin, end, op);
}
token::OpenDelim(token::Brace) => {
if qself.is_some() {
let msg = "unexpected `{` after qualified path";
let mut err = self.fatal(msg);
err.span_label(self.span, msg);
return Err(err);
}
// Parse struct pattern
self.bump();
let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
e.emit();
self.recover_stmt();
(vec![], false)
});
self.bump();
pat = PatKind::Struct(path, fields, etc);
}
token::OpenDelim(token::Paren) => {
if qself.is_some() {
let msg = "unexpected `(` after qualified path";
let mut err = self.fatal(msg);
err.span_label(self.span, msg);
return Err(err);
}
// Parse tuple struct or enum pattern
let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
pat = PatKind::TupleStruct(path, fields, ddpos)
}
_ => pat = PatKind::Path(qself, path),
}
} else {
// Try to parse everything else as literal with optional minus
match self.parse_literal_maybe_minus() {
Ok(begin) => {
let op_span = self.span;
if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
self.check(&token::DotDotDot) {
let end_kind = if self.eat(&token::DotDotDot) {
RangeEnd::Included(RangeSyntax::DotDotDot)
} else if self.eat(&token::DotDotEq) {
RangeEnd::Included(RangeSyntax::DotDotEq)
} else if self.eat(&token::DotDot) {
RangeEnd::Excluded
} else {
panic!("impossible case: we already matched \
on a range-operator token")
};
let end = self.parse_pat_range_end()?;
let op = Spanned { span: op_span, node: end_kind };
pat = PatKind::Range(begin, end, op);
} else {
pat = PatKind::Lit(begin);
}
}
Err(mut err) => {
self.cancel(&mut err);
let expected = expected.unwrap_or("pattern");
let msg = format!(
"expected {}, found {}",
expected,
self.this_token_descr(),
);
let mut err = self.fatal(&msg);
err.span_label(self.span, format!("expected {}", expected));
return Err(err);
}
}
}
}
let pat = Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID };
let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
if !allow_range_pat {
match pat.node {
PatKind::Range(
_, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
) => {},
PatKind::Range(..) => {
let mut err = self.struct_span_err(
pat.span,
"the range pattern here has ambiguous interpretation",
);
err.span_suggestion(
pat.span,
"add parentheses to clarify the precedence",
format!("({})", pprust::pat_to_string(&pat)),
// "ambiguous interpretation" implies that we have to be guessing
Applicability::MaybeIncorrect
);
return Err(err);
}
_ => {}
}
}
Ok(P(pat))
}
/// Parses `ident` or `ident @ pat`.
/// used by the copy foo and ref foo patterns to give a good
/// error message when parsing mistakes like `ref foo(a, b)`.
fn parse_pat_ident(&mut self,
binding_mode: ast::BindingMode)
-> PResult<'a, PatKind> {
let ident = self.parse_ident()?;
let sub = if self.eat(&token::At) {
Some(self.parse_pat(Some("binding pattern"))?)
} else {
None
};
// just to be friendly, if they write something like
// ref Some(i)
// we end up here with ( as the current token. This shortly
// leads to a parse error. Note that if there is no explicit
// binding mode then we do not end up here, because the lookahead
// will direct us over to parse_enum_variant()
if self.token == token::OpenDelim(token::Paren) {
return Err(self.span_fatal(
self.prev_span,
"expected identifier, found enum pattern"))
}
Ok(PatKind::Ident(binding_mode, ident, sub))
}
/// Parses a local variable declaration.
fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
let lo = self.prev_span;
let pat = self.parse_top_level_pat()?;
let (err, ty) = if self.eat(&token::Colon) {
// Save the state of the parser before parsing type normally, in case there is a `:`
// instead of an `=` typo.
let parser_snapshot_before_type = self.clone();
let colon_sp = self.prev_span;
match self.parse_ty() {
Ok(ty) => (None, Some(ty)),
Err(mut err) => {
// Rewind to before attempting to parse the type and continue parsing
let parser_snapshot_after_type = self.clone();
mem::replace(self, parser_snapshot_before_type);
let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
(Some((parser_snapshot_after_type, colon_sp, err)), None)
}
}
} else {
(None, None)
};
let init = match (self.parse_initializer(err.is_some()), err) {
(Ok(init), None) => { // init parsed, ty parsed
init
}
(Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
// Could parse the type as if it were the initializer, it is likely there was a
// typo in the code: `:` instead of `=`. Add suggestion and emit the error.
err.span_suggestion_short(
colon_sp,
"use `=` if you meant to assign",
"=".to_string(),
Applicability::MachineApplicable
);
err.emit();
// As this was parsed successfully, continue as if the code has been fixed for the
// rest of the file. It will still fail due to the emitted error, but we avoid
// extra noise.
init
}
(Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
init_err.cancel();
// Couldn't parse the type nor the initializer, only raise the type error and
// return to the parser state before parsing the type as the initializer.
// let x: <parse_error>;
mem::replace(self, snapshot);
return Err(ty_err);
}
(Err(err), None) => { // init error, ty parsed
// Couldn't parse the initializer and we're not attempting to recover a failed
// parse of the type, return the error.
return Err(err);
}
};
let hi = if self.token == token::Semi {
self.span
} else {
self.prev_span
};
Ok(P(ast::Local {
ty,
pat,
init,
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
attrs,
}))
}
/// Parses a structure field.
fn parse_name_and_ty(&mut self,
lo: Span,
vis: Visibility,
attrs: Vec<Attribute>)
-> PResult<'a, StructField> {
let name = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
Ok(StructField {
span: lo.to(self.prev_span),
ident: Some(name),
vis,
id: ast::DUMMY_NODE_ID,
ty,
attrs,
})
}
/// Emits an expected-item-after-attributes error.
fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
let message = match attrs.last() {
Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
_ => "expected item after attributes",
};
let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
if attrs.last().unwrap().is_sugared_doc {
err.span_label(self.prev_span, "this doc comment doesn't document anything");
}
Err(err)
}
/// Parse a statement. This stops just before trailing semicolons on everything but items.
/// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
Ok(self.parse_stmt_(true))
}
// Eat tokens until we can be relatively sure we reached the end of the
// statement. This is something of a best-effort heuristic.
//
// We terminate when we find an unmatched `}` (without consuming it).
fn recover_stmt(&mut self) {
self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
}
// If `break_on_semi` is `Break`, then we will stop consuming tokens after
// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
// approximate - it can mean we break too early due to macros, but that
// should only lead to sub-optimal recovery, not inaccurate parsing).
//
// If `break_on_block` is `Break`, then we will stop consuming tokens
// after finding (and consuming) a brace-delimited block.
fn recover_stmt_(&mut self, break_on_semi: SemiColonMode, break_on_block: BlockMode) {
let mut brace_depth = 0;
let mut bracket_depth = 0;
let mut in_block = false;
debug!("recover_stmt_ enter loop (semi={:?}, block={:?})",
break_on_semi, break_on_block);
loop {
debug!("recover_stmt_ loop {:?}", self.token);
match self.token {
token::OpenDelim(token::DelimToken::Brace) => {
brace_depth += 1;
self.bump();
if break_on_block == BlockMode::Break &&
brace_depth == 1 &&
bracket_depth == 0 {
in_block = true;
}
}
token::OpenDelim(token::DelimToken::Bracket) => {
bracket_depth += 1;
self.bump();
}
token::CloseDelim(token::DelimToken::Brace) => {
if brace_depth == 0 {
debug!("recover_stmt_ return - close delim {:?}", self.token);
break;
}
brace_depth -= 1;
self.bump();
if in_block && bracket_depth == 0 && brace_depth == 0 {
debug!("recover_stmt_ return - block end {:?}", self.token);
break;
}
}
token::CloseDelim(token::DelimToken::Bracket) => {
bracket_depth -= 1;
if bracket_depth < 0 {
bracket_depth = 0;
}
self.bump();
}
token::Eof => {
debug!("recover_stmt_ return - Eof");
break;
}
token::Semi => {
self.bump();
if break_on_semi == SemiColonMode::Break &&
brace_depth == 0 &&
bracket_depth == 0 {
debug!("recover_stmt_ return - Semi");
break;
}
}
token::Comma => {
if break_on_semi == SemiColonMode::Comma &&
brace_depth == 0 &&
bracket_depth == 0 {
debug!("recover_stmt_ return - Semi");
break;
} else {
self.bump();
}
}
_ => {
self.bump()
}
}
}
}
fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
e.emit();
self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
None
})
}
fn is_async_block(&mut self) -> bool {
self.token.is_keyword(keywords::Async) &&
(
( // `async move {`
self.look_ahead(1, |t| t.is_keyword(keywords::Move)) &&
self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
) || ( // `async {`
self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
)
)
}
fn is_do_catch_block(&mut self) -> bool {
self.token.is_keyword(keywords::Do) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Catch)) &&
self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
!self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
}
fn is_try_block(&mut self) -> bool {
self.token.is_keyword(keywords::Try) &&
self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
self.span.rust_2018() &&
// prevent `while try {} {}`, `if try {} {} else {}`, etc.
!self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
}
fn is_union_item(&self) -> bool {
self.token.is_keyword(keywords::Union) &&
self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
}
fn is_crate_vis(&self) -> bool {
self.token.is_keyword(keywords::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
}
fn is_existential_type_decl(&self) -> bool {
self.token.is_keyword(keywords::Existential) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Type))
}
fn is_auto_trait_item(&mut self) -> bool {
// auto trait
(self.token.is_keyword(keywords::Auto)
&& self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
|| // unsafe auto trait
(self.token.is_keyword(keywords::Unsafe) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Auto)) &&
self.look_ahead(2, |t| t.is_keyword(keywords::Trait)))
}
fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
-> PResult<'a, Option<P<Item>>> {
let token_lo = self.span;
let (ident, def) = match self.token {
token::Ident(ident, false) if ident.name == keywords::Macro.name() => {
self.bump();
let ident = self.parse_ident()?;
let tokens = if self.check(&token::OpenDelim(token::Brace)) {
match self.parse_token_tree() {
TokenTree::Delimited(_, _, tts) => tts,
_ => unreachable!(),
}
} else if self.check(&token::OpenDelim(token::Paren)) {
let args = self.parse_token_tree();
let body = if self.check(&token::OpenDelim(token::Brace)) {
self.parse_token_tree()
} else {
self.unexpected()?;
unreachable!()
};
TokenStream::new(vec![
args.into(),
TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
body.into(),
])
} else {
self.unexpected()?;
unreachable!()
};
(ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
}
token::Ident(ident, _) if ident.name == "macro_rules" &&
self.look_ahead(1, |t| *t == token::Not) => {
let prev_span = self.prev_span;
self.complain_if_pub_macro(&vis.node, prev_span);
self.bump();
self.bump();
let ident = self.parse_ident()?;
let (delim, tokens) = self.expect_delimited_token_tree()?;
if delim != MacDelimiter::Brace {
if !self.eat(&token::Semi) {
let msg = "macros that expand to items must either \
be surrounded with braces or followed by a semicolon";
self.span_err(self.prev_span, msg);
}
}
(ident, ast::MacroDef { tokens: tokens, legacy: true })
}
_ => return Ok(None),
};
let span = lo.to(self.prev_span);
Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
}
fn parse_stmt_without_recovery(&mut self,
macro_legacy_warnings: bool)
-> PResult<'a, Option<Stmt>> {
maybe_whole!(self, NtStmt, |x| Some(x));
let attrs = self.parse_outer_attributes()?;
let lo = self.span;
Ok(Some(if self.eat_keyword(keywords::Let) {
Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Local(self.parse_local(attrs.into())?),
span: lo.to(self.prev_span),
}
} else if let Some(macro_def) = self.eat_macro_def(
&attrs,
&source_map::respan(lo, VisibilityKind::Inherited),
lo,
)? {
Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Item(macro_def),
span: lo.to(self.prev_span),
}
// Starts like a simple path, being careful to avoid contextual keywords
// such as a union items, item with `crate` visibility or auto trait items.
// Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
// like a path (1 token), but it fact not a path.
// `union::b::c` - path, `union U { ... }` - not a path.
// `crate::b::c` - path, `crate struct S;` - not a path.
} else if self.token.is_path_start() &&
!self.token.is_qpath_start() &&
!self.is_union_item() &&
!self.is_crate_vis() &&
!self.is_existential_type_decl() &&
!self.is_auto_trait_item() {
let pth = self.parse_path(PathStyle::Expr)?;
if !self.eat(&token::Not) {
let expr = if self.check(&token::OpenDelim(token::Brace)) {
self.parse_struct_expr(lo, pth, ThinVec::new())?
} else {
let hi = self.prev_span;
self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
};
let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
})?;
return Ok(Some(Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Expr(expr),
span: lo.to(self.prev_span),
}));
}
// it's a macro invocation
let id = match self.token {
token::OpenDelim(_) => keywords::Invalid.ident(), // no special identifier
_ => self.parse_ident()?,
};
// check that we're pointing at delimiters (need to check
// again after the `if`, because of `parse_ident`
// consuming more tokens).
match self.token {
token::OpenDelim(_) => {}
_ => {
// we only expect an ident if we didn't parse one
// above.
let ident_str = if id.name == keywords::Invalid.name() {
"identifier, "
} else {
""
};
let tok_str = self.this_token_descr();
let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}",
ident_str,
tok_str));
err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str));
return Err(err)
},
}
let (delim, tts) = self.expect_delimited_token_tree()?;
let hi = self.prev_span;
let style = if delim == MacDelimiter::Brace {
MacStmtStyle::Braces
} else {
MacStmtStyle::NoBraces
};
if id.name == keywords::Invalid.name() {
let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
let node = if delim == MacDelimiter::Brace ||
self.token == token::Semi || self.token == token::Eof {
StmtKind::Mac(P((mac, style, attrs.into())))
}
// We used to incorrectly stop parsing macro-expanded statements here.
// If the next token will be an error anyway but could have parsed with the
// earlier behavior, stop parsing here and emit a warning to avoid breakage.
else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
// These can continue an expression, so we can't stop parsing and warn.
token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
token::BinOp(token::Minus) | token::BinOp(token::Star) |
token::BinOp(token::And) | token::BinOp(token::Or) |
token::AndAnd | token::OrOr |
token::DotDot | token::DotDotDot | token::DotDotEq => false,
_ => true,
} {
self.warn_missing_semicolon();
StmtKind::Mac(P((mac, style, attrs.into())))
} else {
let e = self.mk_mac_expr(lo.to(hi), mac.node, ThinVec::new());
let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
StmtKind::Expr(e)
};
Stmt {
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
node,
}
} else {
// if it has a special ident, it's definitely an item
//
// Require a semicolon or braces.
if style != MacStmtStyle::Braces {
if !self.eat(&token::Semi) {
self.span_err(self.prev_span,
"macros that expand to items must \
either be surrounded with braces or \
followed by a semicolon");
}
}
let span = lo.to(hi);
Stmt {
id: ast::DUMMY_NODE_ID,
span,
node: StmtKind::Item({
self.mk_item(
span, id /*id is good here*/,
ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
respan(lo, VisibilityKind::Inherited),
attrs)
}),
}
}
} else {
// FIXME: Bad copy of attrs
let old_directory_ownership =
mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
let item = self.parse_item_(attrs.clone(), false, true)?;
self.directory.ownership = old_directory_ownership;
match item {
Some(i) => Stmt {
id: ast::DUMMY_NODE_ID,
span: lo.to(i.span),
node: StmtKind::Item(i),
},
None => {
let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
if !attrs.is_empty() {
if s.prev_token_kind == PrevTokenKind::DocComment {
s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
} else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
s.span_err(s.span, "expected statement after outer attribute");
}
}
};
// Do not attempt to parse an expression if we're done here.
if self.token == token::Semi {
unused_attrs(&attrs, self);
self.bump();
return Ok(None);
}
if self.token == token::CloseDelim(token::Brace) {
unused_attrs(&attrs, self);
return Ok(None);
}
// Remainder are line-expr stmts.
let e = self.parse_expr_res(
Restrictions::STMT_EXPR, Some(attrs.into()))?;
Stmt {
id: ast::DUMMY_NODE_ID,
span: lo.to(e.span),
node: StmtKind::Expr(e),
}
}
}
}))
}
/// Checks if this expression is a successfully parsed statement.
fn expr_is_complete(&mut self, e: &Expr) -> bool {
self.restrictions.contains(Restrictions::STMT_EXPR) &&
!classify::expr_requires_semi_to_be_stmt(e)
}
/// Parses a block. No inner attributes are allowed.
pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
maybe_whole!(self, NtBlock, |x| x);
let lo = self.span;
if !self.eat(&token::OpenDelim(token::Brace)) {
let sp = self.span;
let tok = self.this_token_descr();
let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
let do_not_suggest_help =
self.token.is_keyword(keywords::In) || self.token == token::Colon;
if self.token.is_ident_named("and") {
e.span_suggestion_short(
self.span,
"use `&&` instead of `and` for the boolean operator",
"&&".to_string(),
Applicability::MaybeIncorrect,
);
}
if self.token.is_ident_named("or") {
e.span_suggestion_short(
self.span,
"use `||` instead of `or` for the boolean operator",
"||".to_string(),
Applicability::MaybeIncorrect,
);
}
// Check to see if the user has written something like
//
// if (cond)
// bar;
//
// Which is valid in other languages, but not Rust.
match self.parse_stmt_without_recovery(false) {
Ok(Some(stmt)) => {
if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
|| do_not_suggest_help {
// if the next token is an open brace (e.g., `if a b {`), the place-
// inside-a-block suggestion would be more likely wrong than right
e.span_label(sp, "expected `{`");
return Err(e);
}
let mut stmt_span = stmt.span;
// expand the span to include the semicolon, if it exists
if self.eat(&token::Semi) {
stmt_span = stmt_span.with_hi(self.prev_span.hi());
}
let sugg = pprust::to_string(|s| {
use crate::print::pprust::{PrintState, INDENT_UNIT};
s.ibox(INDENT_UNIT)?;
s.bopen()?;
s.print_stmt(&stmt)?;
s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
});
e.span_suggestion(
stmt_span,
"try placing this code inside a block",
sugg,
// speculative, has been misleading in the past (closed Issue #46836)
Applicability::MaybeIncorrect
);
}
Err(mut e) => {
self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
self.cancel(&mut e);
}
_ => ()
}
e.span_label(sp, "expected `{`");
return Err(e);
}
self.parse_block_tail(lo, BlockCheckMode::Default)
}
/// Parses a block. Inner attributes are allowed.
fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
let lo = self.span;
self.expect(&token::OpenDelim(token::Brace))?;
Ok((self.parse_inner_attributes()?,
self.parse_block_tail(lo, BlockCheckMode::Default)?))
}
/// Parses the rest of a block expression or function body.
/// Precondition: already parsed the '{'.
fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
let mut stmts = vec![];
while !self.eat(&token::CloseDelim(token::Brace)) {
let stmt = match self.parse_full_stmt(false) {
Err(mut err) => {
err.emit();
self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
Some(Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Expr(DummyResult::raw_expr(self.span, true)),
span: self.span,
})
}
Ok(stmt) => stmt,
};
if let Some(stmt) = stmt {
stmts.push(stmt);
} else if self.token == token::Eof {
break;
} else {
// Found only `;` or `}`.
continue;
};
}
Ok(P(ast::Block {
stmts,
id: ast::DUMMY_NODE_ID,
rules: s,
span: lo.to(self.prev_span),
}))
}
/// Parses a statement, including the trailing semicolon.
crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
// skip looking for a trailing semicolon when we have an interpolated statement
maybe_whole!(self, NtStmt, |x| Some(x));
let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
Some(stmt) => stmt,
None => return Ok(None),
};
match stmt.node {
StmtKind::Expr(ref expr) if self.token != token::Eof => {
// expression without semicolon
if classify::expr_requires_semi_to_be_stmt(expr) {
// Just check for errors and recover; do not eat semicolon yet.
if let Err(mut e) =
self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
{
e.emit();
self.recover_stmt();
}
}
}
StmtKind::Local(..) => {
// We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
if macro_legacy_warnings && self.token != token::Semi {
self.warn_missing_semicolon();
} else {
self.expect_one_of(&[], &[token::Semi])?;
}
}
_ => {}
}
if self.eat(&token::Semi) {
stmt = stmt.add_trailing_semicolon();
}
stmt.span = stmt.span.with_hi(self.prev_span.hi());
Ok(Some(stmt))
}
fn warn_missing_semicolon(&self) {
self.diagnostic().struct_span_warn(self.span, {
&format!("expected `;`, found {}", self.this_token_descr())
}).note({
"This was erroneously allowed and will become a hard error in a future release"
}).emit();
}
fn err_dotdotdot_syntax(&self, span: Span) {
self.diagnostic().struct_span_err(span, {
"unexpected token: `...`"
}).span_suggestion(
span, "use `..` for an exclusive range", "..".to_owned(),
Applicability::MaybeIncorrect
).span_suggestion(
span, "or `..=` for an inclusive range", "..=".to_owned(),
Applicability::MaybeIncorrect
).emit();
}
/// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
///
/// ```
/// BOUND = TY_BOUND | LT_BOUND
/// LT_BOUND = LIFETIME (e.g., `'a`)
/// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
/// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
/// ```
fn parse_generic_bounds_common(&mut self,
allow_plus: bool,
colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
let mut bounds = Vec::new();
let mut negative_bounds = Vec::new();
let mut last_plus_span = None;
loop {
// This needs to be synchronized with `Token::can_begin_bound`.
let is_bound_start = self.check_path() || self.check_lifetime() ||
self.check(&token::Not) || // used for error reporting only
self.check(&token::Question) ||
self.check_keyword(keywords::For) ||
self.check(&token::OpenDelim(token::Paren));
if is_bound_start {
let lo = self.span;
let has_parens = self.eat(&token::OpenDelim(token::Paren));
let inner_lo = self.span;
let is_negative = self.eat(&token::Not);
let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
if self.token.is_lifetime() {
if let Some(question_span) = question {
self.span_err(question_span,
"`?` may only modify trait bounds, not lifetime bounds");
}
bounds.push(GenericBound::Outlives(self.expect_lifetime()));
if has_parens {
let inner_span = inner_lo.to(self.prev_span);
self.expect(&token::CloseDelim(token::Paren))?;
let mut err = self.struct_span_err(
lo.to(self.prev_span),
"parenthesized lifetime bounds are not supported"
);
if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) {
err.span_suggestion_short(
lo.to(self.prev_span),
"remove the parentheses",
snippet.to_owned(),
Applicability::MachineApplicable
);
}
err.emit();
}
} else {
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
let path = self.parse_path(PathStyle::Type)?;
if has_parens {
self.expect(&token::CloseDelim(token::Paren))?;
}
let poly_span = lo.to(self.prev_span);
if is_negative {
negative_bounds.push(
last_plus_span.or(colon_span).unwrap()
.to(poly_span));
} else {
let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
let modifier = if question.is_some() {
TraitBoundModifier::Maybe
} else {
TraitBoundModifier::None
};
bounds.push(GenericBound::Trait(poly_trait, modifier));
}
}
} else {
break
}
if !allow_plus || !self.eat_plus() {
break
} else {
last_plus_span = Some(self.prev_span);
}
}
if !negative_bounds.is_empty() {
let plural = negative_bounds.len() > 1;
let mut err = self.struct_span_err(negative_bounds,
"negative trait bounds are not supported");
let bound_list = colon_span.unwrap().to(self.prev_span);
let mut new_bound_list = String::new();
if !bounds.is_empty() {
let mut snippets = bounds.iter().map(|bound| bound.span())
.map(|span| self.sess.source_map().span_to_snippet(span));
while let Some(Ok(snippet)) = snippets.next() {
new_bound_list.push_str(" + ");
new_bound_list.push_str(&snippet);
}
new_bound_list = new_bound_list.replacen(" +", ":", 1);
}
err.span_suggestion_short(bound_list,
&format!("remove the trait bound{}",
if plural { "s" } else { "" }),
new_bound_list,
Applicability::MachineApplicable);
err.emit();
}
return Ok(bounds);
}
fn parse_generic_bounds(&mut self, colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
self.parse_generic_bounds_common(true, colon_span)
}
/// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
///
/// ```
/// BOUND = LT_BOUND (e.g., `'a`)
/// ```
fn parse_lt_param_bounds(&mut self) -> GenericBounds {
let mut lifetimes = Vec::new();
while self.check_lifetime() {
lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
if !self.eat_plus() {
break
}
}
lifetimes
}
/// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
fn parse_ty_param(&mut self,
preceding_attrs: Vec<Attribute>)
-> PResult<'a, GenericParam> {
let ident = self.parse_ident()?;
// Parse optional colon and param bounds.
let bounds = if self.eat(&token::Colon) {
self.parse_generic_bounds(None)?
} else {
Vec::new()
};
let default = if self.eat(&token::Eq) {
Some(self.parse_ty()?)
} else {
None
};
Ok(GenericParam {
ident,
id: ast::DUMMY_NODE_ID,
attrs: preceding_attrs.into(),
bounds,
kind: GenericParamKind::Type {
default,
}
})
}
/// Parses the following grammar:
///
/// TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
fn parse_trait_item_assoc_ty(&mut self)
-> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
let ident = self.parse_ident()?;
let mut generics = self.parse_generics()?;
// Parse optional colon and param bounds.
let bounds = if self.eat(&token::Colon) {
self.parse_generic_bounds(None)?
} else {
Vec::new()
};
generics.where_clause = self.parse_where_clause()?;
let default = if self.eat(&token::Eq) {
Some(self.parse_ty()?)
} else {
None
};
self.expect(&token::Semi)?;
Ok((ident, TraitItemKind::Type(bounds, default), generics))
}
fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
self.expect_keyword(keywords::Const)?;
let ident = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
Ok(GenericParam {
ident,
id: ast::DUMMY_NODE_ID,
attrs: preceding_attrs.into(),
bounds: Vec::new(),
kind: GenericParamKind::Const {
ty,
}
})
}
/// Parses a (possibly empty) list of lifetime and type parameters, possibly including
/// a trailing comma and erroneous trailing attributes.
crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
let mut params = Vec::new();
loop {
let attrs = self.parse_outer_attributes()?;
if self.check_lifetime() {
let lifetime = self.expect_lifetime();
// Parse lifetime parameter.
let bounds = if self.eat(&token::Colon) {
self.parse_lt_param_bounds()
} else {
Vec::new()
};
params.push(ast::GenericParam {
ident: lifetime.ident,
id: lifetime.id,
attrs: attrs.into(),
bounds,
kind: ast::GenericParamKind::Lifetime,
});
} else if self.check_keyword(keywords::Const) {
// Parse const parameter.
params.push(self.parse_const_param(attrs)?);
} else if self.check_ident() {
// Parse type parameter.
params.push(self.parse_ty_param(attrs)?);
} else {
// Check for trailing attributes and stop parsing.
if !attrs.is_empty() {
if !params.is_empty() {
self.struct_span_err(
attrs[0].span,
&format!("trailing attribute after generic parameter"),
)
.span_label(attrs[0].span, "attributes must go before parameters")
.emit();
} else {
self.struct_span_err(
attrs[0].span,
&format!("attribute without generic parameters"),
)
.span_label(
attrs[0].span,
"attributes are only permitted when preceding parameters",
)
.emit();
}
}
break
}
if !self.eat(&token::Comma) {
break
}
}
Ok(params)
}
/// Parses a set of optional generic type parameter declarations. Where
/// clauses are not parsed here, and must be added later via
/// `parse_where_clause()`.
///
/// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
/// | ( < lifetimes , typaramseq ( , )? > )
/// where typaramseq = ( typaram ) | ( typaram , typaramseq )
fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
maybe_whole!(self, NtGenerics, |x| x);
let span_lo = self.span;
if self.eat_lt() {
let params = self.parse_generic_params()?;
self.expect_gt()?;
Ok(ast::Generics {
params,
where_clause: WhereClause {
id: ast::DUMMY_NODE_ID,
predicates: Vec::new(),
span: syntax_pos::DUMMY_SP,
},
span: span_lo.to(self.prev_span),
})
} else {
Ok(ast::Generics::default())
}
}
/// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
/// For the purposes of understanding the parsing logic of generic arguments, this function
/// can be thought of being the same as just calling `self.parse_generic_args()` if the source
/// had the correct amount of leading angle brackets.
///
/// ```ignore (diagnostics)
/// bar::<<<<T as Foo>::Output>();
/// ^^ help: remove extra angle brackets
/// ```
fn parse_generic_args_with_leaning_angle_bracket_recovery(
&mut self,
style: PathStyle,
lo: Span,
) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
// We need to detect whether there are extra leading left angle brackets and produce an
// appropriate error and suggestion. This cannot be implemented by looking ahead at
// upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
// then there won't be matching `>` tokens to find.
//
// To explain how this detection works, consider the following example:
//
// ```ignore (diagnostics)
// bar::<<<<T as Foo>::Output>();
// ^^ help: remove extra angle brackets
// ```
//
// Parsing of the left angle brackets starts in this function. We start by parsing the
// `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
// `eat_lt`):
//
// *Upcoming tokens:* `<<<<T as Foo>::Output>;`
// *Unmatched count:* 1
// *`parse_path_segment` calls deep:* 0
//
// This has the effect of recursing as this function is called if a `<` character
// is found within the expected generic arguments:
//
// *Upcoming tokens:* `<<<T as Foo>::Output>;`
// *Unmatched count:* 2
// *`parse_path_segment` calls deep:* 1
//
// Eventually we will have recursed until having consumed all of the `<` tokens and
// this will be reflected in the count:
//
// *Upcoming tokens:* `T as Foo>::Output>;`
// *Unmatched count:* 4
// `parse_path_segment` calls deep:* 3
//
// The parser will continue until reaching the first `>` - this will decrement the
// unmatched angle bracket count and return to the parent invocation of this function
// having succeeded in parsing:
//
// *Upcoming tokens:* `::Output>;`
// *Unmatched count:* 3
// *`parse_path_segment` calls deep:* 2
//
// This will continue until the next `>` character which will also return successfully
// to the parent invocation of this function and decrement the count:
//
// *Upcoming tokens:* `;`
// *Unmatched count:* 2
// *`parse_path_segment` calls deep:* 1
//
// At this point, this function will expect to find another matching `>` character but
// won't be able to and will return an error. This will continue all the way up the
// call stack until the first invocation:
//
// *Upcoming tokens:* `;`
// *Unmatched count:* 2
// *`parse_path_segment` calls deep:* 0
//
// In doing this, we have managed to work out how many unmatched leading left angle
// brackets there are, but we cannot recover as the unmatched angle brackets have
// already been consumed. To remedy this, we keep a snapshot of the parser state
// before we do the above. We can then inspect whether we ended up with a parsing error
// and unmatched left angle brackets and if so, restore the parser state before we
// consumed any `<` characters to emit an error and consume the erroneous tokens to
// recover by attempting to parse again.
//
// In practice, the recursion of this function is indirect and there will be other
// locations that consume some `<` characters - as long as we update the count when
// this happens, it isn't an issue.
let is_first_invocation = style == PathStyle::Expr;
// Take a snapshot before attempting to parse - we can restore this later.
let snapshot = if is_first_invocation {
Some(self.clone())
} else {
None
};
debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
match self.parse_generic_args() {
Ok(value) => Ok(value),
Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
// Cancel error from being unable to find `>`. We know the error
// must have been this due to a non-zero unmatched angle bracket
// count.
e.cancel();
// Swap `self` with our backup of the parser state before attempting to parse
// generic arguments.
let snapshot = mem::replace(self, snapshot.unwrap());
debug!(
"parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
snapshot.count={:?}",
snapshot.unmatched_angle_bracket_count,
);
// Eat the unmatched angle brackets.
for _ in 0..snapshot.unmatched_angle_bracket_count {
self.eat_lt();
}
// Make a span over ${unmatched angle bracket count} characters.
let span = lo.with_hi(
lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
);
let plural = snapshot.unmatched_angle_bracket_count > 1;
self.diagnostic()
.struct_span_err(
span,
&format!(
"unmatched angle bracket{}",
if plural { "s" } else { "" }
),
)
.span_suggestion(
span,
&format!(
"remove extra angle bracket{}",
if plural { "s" } else { "" }
),
String::new(),
Applicability::MachineApplicable,
)
.emit();
// Try again without unmatched angle bracket characters.
self.parse_generic_args()
},
Err(e) => Err(e),
}
}
/// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
/// possibly including trailing comma.
fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
let mut args = Vec::new();
let mut bindings = Vec::new();
let mut misplaced_assoc_ty_bindings: Vec<Span> = Vec::new();
let mut assoc_ty_bindings: Vec<Span> = Vec::new();
let args_lo = self.span;
loop {
if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
// Parse lifetime argument.
args.push(GenericArg::Lifetime(self.expect_lifetime()));
misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
} else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
// Parse associated type binding.
let lo = self.span;
let ident = self.parse_ident()?;
self.bump();
let ty = self.parse_ty()?;
let span = lo.to(self.prev_span);
bindings.push(TypeBinding {
id: ast::DUMMY_NODE_ID,
ident,
ty,
span,
});
assoc_ty_bindings.push(span);
} else if self.check_const_arg() {
// FIXME(const_generics): to distinguish between idents for types and consts,
// we should introduce a GenericArg::Ident in the AST and distinguish when
// lowering to the HIR. For now, idents for const args are not permitted.
// Parse const argument.
let expr = if let token::OpenDelim(token::Brace) = self.token {
self.parse_block_expr(None, self.span, BlockCheckMode::Default, ThinVec::new())?
} else if self.token.is_ident() {
// FIXME(const_generics): to distinguish between idents for types and consts,
// we should introduce a GenericArg::Ident in the AST and distinguish when
// lowering to the HIR. For now, idents for const args are not permitted.
return Err(
self.fatal("identifiers may currently not be used for const generics")
);
} else {
// FIXME(const_generics): this currently conflicts with emplacement syntax
// with negative integer literals.
self.parse_literal_maybe_minus()?
};
let value = AnonConst {
id: ast::DUMMY_NODE_ID,
value: expr,
};
args.push(GenericArg::Const(value));
misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
} else if self.check_type() {
// Parse type argument.
args.push(GenericArg::Type(self.parse_ty()?));
misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
} else {
break
}
if !self.eat(&token::Comma) {
break
}
}
// FIXME: we would like to report this in ast_validation instead, but we currently do not
// preserve ordering of generic parameters with respect to associated type binding, so we
// lose that information after parsing.
if misplaced_assoc_ty_bindings.len() > 0 {
let mut err = self.struct_span_err(
args_lo.to(self.prev_span),
"associated type bindings must be declared after generic parameters",
);
for span in misplaced_assoc_ty_bindings {
err.span_label(
span,
"this associated type binding should be moved after the generic parameters",
);
}
err.emit();
}
Ok((args, bindings))
}
/// Parses an optional where-clause and places it in `generics`.
///
/// ```ignore (only-for-syntax-highlight)
/// where T : Trait<U, V> + 'b, 'a : 'b
/// ```
fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
maybe_whole!(self, NtWhereClause, |x| x);
let mut where_clause = WhereClause {
id: ast::DUMMY_NODE_ID,
predicates: Vec::new(),
span: syntax_pos::DUMMY_SP,
};
if !self.eat_keyword(keywords::Where) {
return Ok(where_clause);
}
let lo = self.prev_span;
// We are considering adding generics to the `where` keyword as an alternative higher-rank
// parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
// change we parse those generics now, but report an error.
if self.choose_generics_over_qpath() {
let generics = self.parse_generics()?;
self.struct_span_err(
generics.span,
"generic parameters on `where` clauses are reserved for future use",
)
.span_label(generics.span, "currently unsupported")
.emit();
}
loop {
let lo = self.span;
if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
let lifetime = self.expect_lifetime();
// Bounds starting with a colon are mandatory, but possibly empty.
self.expect(&token::Colon)?;
let bounds = self.parse_lt_param_bounds();
where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
ast::WhereRegionPredicate {
span: lo.to(self.prev_span),
lifetime,
bounds,
}
));
} else if self.check_type() {
// Parse optional `for<'a, 'b>`.
// This `for` is parsed greedily and applies to the whole predicate,
// the bounded type can have its own `for` applying only to it.
// Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
// Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
// Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
// Parse type with mandatory colon and (possibly empty) bounds,
// or with mandatory equality sign and the second type.
let ty = self.parse_ty()?;
if self.eat(&token::Colon) {
let bounds = self.parse_generic_bounds(None)?;
where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
ast::WhereBoundPredicate {
span: lo.to(self.prev_span),
bound_generic_params: lifetime_defs,
bounded_ty: ty,
bounds,
}
));
// FIXME: Decide what should be used here, `=` or `==`.
// FIXME: We are just dropping the binders in lifetime_defs on the floor here.
} else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
let rhs_ty = self.parse_ty()?;
where_clause.predicates.push(ast::WherePredicate::EqPredicate(
ast::WhereEqPredicate {
span: lo.to(self.prev_span),
lhs_ty: ty,
rhs_ty,
id: ast::DUMMY_NODE_ID,
}
));
} else {
return self.unexpected();
}
} else {
break
}
if !self.eat(&token::Comma) {
break
}
}
where_clause.span = lo.to(self.prev_span);
Ok(where_clause)
}
fn parse_fn_args(&mut self, named_args: bool, allow_variadic: bool)
-> PResult<'a, (Vec<Arg> , bool)> {
self.expect(&token::OpenDelim(token::Paren))?;
let sp = self.span;
let mut variadic = false;
let (args, recovered): (Vec<Option<Arg>>, bool) =
self.parse_seq_to_before_end(
&token::CloseDelim(token::Paren),
SeqSep::trailing_allowed(token::Comma),
|p| {
if p.token == token::DotDotDot {
p.bump();
variadic = true;
if allow_variadic {
if p.token != token::CloseDelim(token::Paren) {
let span = p.span;
p.span_err(span,
"`...` must be last in argument list for variadic function");
}
Ok(None)
} else {
let span = p.prev_span;
if p.token == token::CloseDelim(token::Paren) {
// continue parsing to present any further errors
p.struct_span_err(
span,
"only foreign functions are allowed to be variadic"
).emit();
Ok(Some(dummy_arg(span)))
} else {
// this function definition looks beyond recovery, stop parsing
p.span_err(span,
"only foreign functions are allowed to be variadic");
Ok(None)
}
}
} else {
match p.parse_arg_general(named_args, false) {
Ok(arg) => Ok(Some(arg)),
Err(mut e) => {
e.emit();
let lo = p.prev_span;
// Skip every token until next possible arg or end.
p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
// Create a placeholder argument for proper arg count (#34264).
let span = lo.to(p.prev_span);
Ok(Some(dummy_arg(span)))
}
}
}
}
)?;
if !recovered {
self.eat(&token::CloseDelim(token::Paren));
}
let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
if variadic && args.is_empty() {
self.span_err(sp,
"variadic function must be declared with at least one named argument");
}
Ok((args, variadic))
}
/// Parses the argument list and result type of a function declaration.
fn parse_fn_decl(&mut self, allow_variadic: bool) -> PResult<'a, P<FnDecl>> {
let (args, variadic) = self.parse_fn_args(true, allow_variadic)?;
let ret_ty = self.parse_ret_ty(true)?;
Ok(P(FnDecl {
inputs: args,
output: ret_ty,
variadic,
}))
}
/// Returns the parsed optional self argument and whether a self shortcut was used.
fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
let expect_ident = |this: &mut Self| match this.token {
// Preserve hygienic context.
token::Ident(ident, _) =>
{ let span = this.span; this.bump(); Ident::new(ident.name, span) }
_ => unreachable!()
};
let isolated_self = |this: &mut Self, n| {
this.look_ahead(n, |t| t.is_keyword(keywords::SelfLower)) &&
this.look_ahead(n + 1, |t| t != &token::ModSep)
};
// Parse optional self parameter of a method.
// Only a limited set of initial token sequences is considered self parameters, anything
// else is parsed as a normal function parameter list, so some lookahead is required.
let eself_lo = self.span;
let (eself, eself_ident, eself_hi) = match self.token {
token::BinOp(token::And) => {
// &self
// &mut self
// &'lt self
// &'lt mut self
// &not_self
(if isolated_self(self, 1) {
self.bump();
SelfKind::Region(None, Mutability::Immutable)
} else if self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) &&
isolated_self(self, 2) {
self.bump();
self.bump();
SelfKind::Region(None, Mutability::Mutable)
} else if self.look_ahead(1, |t| t.is_lifetime()) &&
isolated_self(self, 2) {
self.bump();
let lt = self.expect_lifetime();
SelfKind::Region(Some(lt), Mutability::Immutable)
} else if self.look_ahead(1, |t| t.is_lifetime()) &&
self.look_ahead(2, |t| t.is_keyword(keywords::Mut)) &&
isolated_self(self, 3) {
self.bump();
let lt = self.expect_lifetime();
self.bump();
SelfKind::Region(Some(lt), Mutability::Mutable)
} else {
return Ok(None);
}, expect_ident(self), self.prev_span)
}
token::BinOp(token::Star) => {
// *self
// *const self
// *mut self
// *not_self
// Emit special error for `self` cases.
let msg = "cannot pass `self` by raw pointer";
(if isolated_self(self, 1) {
self.bump();
self.struct_span_err(self.span, msg)
.span_label(self.span, msg)
.emit();
SelfKind::Value(Mutability::Immutable)
} else if self.look_ahead(1, |t| t.is_mutability()) &&
isolated_self(self, 2) {
self.bump();
self.bump();
self.struct_span_err(self.span, msg)
.span_label(self.span, msg)
.emit();
SelfKind::Value(Mutability::Immutable)
} else {
return Ok(None);
}, expect_ident(self), self.prev_span)
}
token::Ident(..) => {
if isolated_self(self, 0) {
// self
// self: TYPE
let eself_ident = expect_ident(self);
let eself_hi = self.prev_span;
(if self.eat(&token::Colon) {
let ty = self.parse_ty()?;
SelfKind::Explicit(ty, Mutability::Immutable)
} else {
SelfKind::Value(Mutability::Immutable)
}, eself_ident, eself_hi)
} else if self.token.is_keyword(keywords::Mut) &&
isolated_self(self, 1) {
// mut self
// mut self: TYPE
self.bump();
let eself_ident = expect_ident(self);
let eself_hi = self.prev_span;
(if self.eat(&token::Colon) {
let ty = self.parse_ty()?;
SelfKind::Explicit(ty, Mutability::Mutable)
} else {
SelfKind::Value(Mutability::Mutable)
}, eself_ident, eself_hi)
} else {
return Ok(None);
}
}
_ => return Ok(None),
};
let eself = source_map::respan(eself_lo.to(eself_hi), eself);
Ok(Some(Arg::from_self(eself, eself_ident)))
}
/// Parses the parameter list and result type of a function that may have a `self` parameter.
fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>>
where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>,
{
self.expect(&token::OpenDelim(token::Paren))?;
// Parse optional self argument
let self_arg = self.parse_self_arg()?;
// Parse the rest of the function parameter list.
let sep = SeqSep::trailing_allowed(token::Comma);
let (fn_inputs, recovered) = if let Some(self_arg) = self_arg {
if self.check(&token::CloseDelim(token::Paren)) {
(vec![self_arg], false)
} else if self.eat(&token::Comma) {
let mut fn_inputs = vec![self_arg];
let (mut input, recovered) = self.parse_seq_to_before_end(
&token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
fn_inputs.append(&mut input);
(fn_inputs, recovered)
} else {
return self.unexpected();
}
} else {
self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
};
if !recovered {
// Parse closing paren and return type.
self.expect(&token::CloseDelim(token::Paren))?;
}
Ok(P(FnDecl {
inputs: fn_inputs,
output: self.parse_ret_ty(true)?,
variadic: false
}))
}
/// Parses the `|arg, arg|` header of a closure.
fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
let inputs_captures = {
if self.eat(&token::OrOr) {
Vec::new()
} else {
self.expect(&token::BinOp(token::Or))?;
let args = self.parse_seq_to_before_tokens(
&[&token::BinOp(token::Or), &token::OrOr],
SeqSep::trailing_allowed(token::Comma),
TokenExpectType::NoExpect,
|p| p.parse_fn_block_arg()
)?.0;
self.expect_or()?;
args
}
};
let output = self.parse_ret_ty(true)?;
Ok(P(FnDecl {
inputs: inputs_captures,
output,
variadic: false
}))
}
/// Parses the name and optional generic types of a function header.
fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
let id = self.parse_ident()?;
let generics = self.parse_generics()?;
Ok((id, generics))
}
fn mk_item(&mut self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
attrs: Vec<Attribute>) -> P<Item> {
P(Item {
ident,
attrs,
id: ast::DUMMY_NODE_ID,
node,
vis,
span,
tokens: None,
})
}
/// Parses an item-position function declaration.
fn parse_item_fn(&mut self,
unsafety: Unsafety,
asyncness: IsAsync,
constness: Spanned<Constness>,
abi: Abi)
-> PResult<'a, ItemInfo> {
let (ident, mut generics) = self.parse_fn_header()?;
let decl = self.parse_fn_decl(false)?;
generics.where_clause = self.parse_where_clause()?;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
let header = FnHeader { unsafety, asyncness, constness, abi };
Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
}
/// Returns `true` if we are looking at `const ID`
/// (returns `false` for things like `const fn`, etc.).
fn is_const_item(&mut self) -> bool {
self.token.is_keyword(keywords::Const) &&
!self.look_ahead(1, |t| t.is_keyword(keywords::Fn)) &&
!self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe))
}
/// Parses all the "front matter" for a `fn` declaration, up to
/// and including the `fn` keyword:
///
/// - `const fn`
/// - `unsafe fn`
/// - `const unsafe fn`
/// - `extern fn`
/// - etc.
fn parse_fn_front_matter(&mut self)
-> PResult<'a, (
Spanned<Constness>,
Unsafety,
IsAsync,
Abi
)>
{
let is_const_fn = self.eat_keyword(keywords::Const);
let const_span = self.prev_span;
let unsafety = self.parse_unsafety();
let asyncness = self.parse_asyncness();
let (constness, unsafety, abi) = if is_const_fn {
(respan(const_span, Constness::Const), unsafety, Abi::Rust)
} else {
let abi = if self.eat_keyword(keywords::Extern) {
self.parse_opt_abi()?.unwrap_or(Abi::C)
} else {
Abi::Rust
};
(respan(self.prev_span, Constness::NotConst), unsafety, abi)
};
self.expect_keyword(keywords::Fn)?;
Ok((constness, unsafety, asyncness, abi))
}
/// Parses an impl item.
pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
maybe_whole!(self, NtImplItem, |x| x);
let attrs = self.parse_outer_attributes()?;
let (mut item, tokens) = self.collect_tokens(|this| {
this.parse_impl_item_(at_end, attrs)
})?;
// See `parse_item` for why this clause is here.
if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
item.tokens = Some(tokens);
}
Ok(item)
}
fn parse_impl_item_(&mut self,
at_end: &mut bool,
mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
let lo = self.span;
let vis = self.parse_visibility(false)?;
let defaultness = self.parse_defaultness();
let (name, node, generics) = if let Some(type_) = self.eat_type() {
let (name, alias, generics) = type_?;
let kind = match alias {
AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
};
(name, kind, generics)
} else if self.is_const_item() {
// This parses the grammar:
// ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
self.expect_keyword(keywords::Const)?;
let name = self.parse_ident()?;
self.expect(&token::Colon)?;
let typ = self.parse_ty()?;
self.expect(&token::Eq)?;
let expr = self.parse_expr()?;
self.expect(&token::Semi)?;
(name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
} else {
let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
attrs.extend(inner_attrs);
(name, node, generics)
};
Ok(ImplItem {
id: ast::DUMMY_NODE_ID,
span: lo.to(self.prev_span),
ident: name,
vis,
defaultness,
attrs,
generics,
node,
tokens: None,
})
}
fn complain_if_pub_macro(&mut self, vis: &VisibilityKind, sp: Span) {
match *vis {
VisibilityKind::Inherited => {}
_ => {
let is_macro_rules: bool = match self.token {
token::Ident(sid, _) => sid.name == Symbol::intern("macro_rules"),
_ => false,
};
let mut err = if is_macro_rules {
let mut err = self.diagnostic()
.struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
err.span_suggestion(
sp,
"try exporting the macro",
"#[macro_export]".to_owned(),
Applicability::MaybeIncorrect // speculative
);
err
} else {
let mut err = self.diagnostic()
.struct_span_err(sp, "can't qualify macro invocation with `pub`");
err.help("try adjusting the macro to put `pub` inside the invocation");
err
};
err.emit();
}
}
}
fn missing_assoc_item_kind_err(&mut self, item_type: &str, prev_span: Span)
-> DiagnosticBuilder<'a>
{
let expected_kinds = if item_type == "extern" {
"missing `fn`, `type`, or `static`"
} else {
"missing `fn`, `type`, or `const`"
};
// Given this code `path(`, it seems like this is not
// setting the visibility of a macro invocation, but rather
// a mistyped method declaration.
// Create a diagnostic pointing out that `fn` is missing.
//
// x | pub path(&self) {
// | ^ missing `fn`, `type`, or `const`
// pub path(
// ^^ `sp` below will point to this
let sp = prev_span.between(self.prev_span);
let mut err = self.diagnostic().struct_span_err(
sp,
&format!("{} for {}-item declaration",
expected_kinds, item_type));
err.span_label(sp, expected_kinds);
err
}
/// Parse a method or a macro invocation in a trait impl.
fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
-> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
ast::ImplItemKind)> {
// code copied from parse_macro_use_or_failure... abstraction!
if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
// method macro
Ok((keywords::Invalid.ident(), vec![], ast::Generics::default(),
ast::ImplItemKind::Macro(mac)))
} else {
let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
let ident = self.parse_ident()?;
let mut generics = self.parse_generics()?;
let decl = self.parse_fn_decl_with_self(|p| p.parse_arg())?;
generics.where_clause = self.parse_where_clause()?;
*at_end = true;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
let header = ast::FnHeader { abi, unsafety, constness, asyncness };
Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
ast::MethodSig { header, decl },
body
)))
}
}
/// Parses `trait Foo { ... }` or `trait Foo = Bar;`.
fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
let ident = self.parse_ident()?;
let mut tps = self.parse_generics()?;
// Parse optional colon and supertrait bounds.
let bounds = if self.eat(&token::Colon) {
self.parse_generic_bounds(Some(self.prev_span))?
} else {
Vec::new()
};
if self.eat(&token::Eq) {
// it's a trait alias
let bounds = self.parse_generic_bounds(None)?;
tps.where_clause = self.parse_where_clause()?;
self.expect(&token::Semi)?;
if is_auto == IsAuto::Yes {
let msg = "trait aliases cannot be `auto`";
self.struct_span_err(self.prev_span, msg)
.span_label(self.prev_span, msg)
.emit();
}
if unsafety != Unsafety::Normal {
let msg = "trait aliases cannot be `unsafe`";
self.struct_span_err(self.prev_span, msg)
.span_label(self.prev_span, msg)
.emit();
}
Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
} else {
// it's a normal trait
tps.where_clause = self.parse_where_clause()?;
self.expect(&token::OpenDelim(token::Brace))?;
let mut trait_items = vec![];
while !self.eat(&token::CloseDelim(token::Brace)) {
let mut at_end = false;
match self.parse_trait_item(&mut at_end) {
Ok(item) => trait_items.push(item),
Err(mut e) => {
e.emit();
if !at_end {
self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
}
}
}
}
Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
}
}
fn choose_generics_over_qpath(&self) -> bool {
// There's an ambiguity between generic parameters and qualified paths in impls.
// If we see `<` it may start both, so we have to inspect some following tokens.
// The following combinations can only start generics,
// but not qualified paths (with one exception):
// `<` `>` - empty generic parameters
// `<` `#` - generic parameters with attributes
// `<` (LIFETIME|IDENT) `>` - single generic parameter
// `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
// `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
// `<` (LIFETIME|IDENT) `=` - generic parameter with a default
// `<` const - generic const parameter
// The only truly ambiguous case is
// `<` IDENT `>` `::` IDENT ...
// we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
// because this is what almost always expected in practice, qualified paths in impls
// (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
self.token == token::Lt &&
(self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
t == &token::Colon || t == &token::Eq) ||
self.look_ahead(1, |t| t.is_keyword(keywords::Const)))
}
fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
self.expect(&token::OpenDelim(token::Brace))?;
let attrs = self.parse_inner_attributes()?;
let mut impl_items = Vec::new();
while !self.eat(&token::CloseDelim(token::Brace)) {
let mut at_end = false;
match self.parse_impl_item(&mut at_end) {
Ok(impl_item) => impl_items.push(impl_item),
Err(mut err) => {
err.emit();
if !at_end {
self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
}
}
}
}
Ok((impl_items, attrs))
}
/// Parses an implementation item, `impl` keyword is already parsed.
///
/// impl<'a, T> TYPE { /* impl items */ }
/// impl<'a, T> TRAIT for TYPE { /* impl items */ }
/// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
///
/// We actually parse slightly more relaxed grammar for better error reporting and recovery.
/// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
/// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
-> PResult<'a, ItemInfo> {
// First, parse generic parameters if necessary.
let mut generics = if self.choose_generics_over_qpath() {
self.parse_generics()?
} else {
ast::Generics::default()
};
// Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
self.bump(); // `!`
ast::ImplPolarity::Negative
} else {
ast::ImplPolarity::Positive
};
// Parse both types and traits as a type, then reinterpret if necessary.
let ty_first = self.parse_ty()?;
// If `for` is missing we try to recover.
let has_for = self.eat_keyword(keywords::For);
let missing_for_span = self.prev_span.between(self.span);
let ty_second = if self.token == token::DotDot {
// We need to report this error after `cfg` expansion for compatibility reasons
self.bump(); // `..`, do not add it to expected tokens
Some(P(Ty { node: TyKind::Err, span: self.prev_span, id: ast::DUMMY_NODE_ID }))
} else if has_for || self.token.can_begin_type() {
Some(self.parse_ty()?)
} else {
None
};
generics.where_clause = self.parse_where_clause()?;
let (impl_items, attrs) = self.parse_impl_body()?;
let item_kind = match ty_second {
Some(ty_second) => {
// impl Trait for Type
if !has_for {
self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
.span_suggestion_short(
missing_for_span,
"add `for` here",
" for ".to_string(),
Applicability::MachineApplicable,
).emit();
}
let ty_first = ty_first.into_inner();
let path = match ty_first.node {
// This notably includes paths passed through `ty` macro fragments (#46438).
TyKind::Path(None, path) => path,
_ => {
self.span_err(ty_first.span, "expected a trait, found type");
ast::Path::from_ident(Ident::new(keywords::Invalid.name(), ty_first.span))
}
};
let trait_ref = TraitRef { path, ref_id: ty_first.id };
ItemKind::Impl(unsafety, polarity, defaultness,
generics, Some(trait_ref), ty_second, impl_items)
}
None => {
// impl Type
ItemKind::Impl(unsafety, polarity, defaultness,
generics, None, ty_first, impl_items)
}
};
Ok((keywords::Invalid.ident(), item_kind, Some(attrs)))
}
fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
if self.eat_keyword(keywords::For) {
self.expect_lt()?;
let params = self.parse_generic_params()?;
self.expect_gt()?;
// We rely on AST validation to rule out invalid cases: There must not be type
// parameters, and the lifetime parameters must not have bounds.
Ok(params)
} else {
Ok(Vec::new())
}
}
/// Parses `struct Foo { ... }`.
fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
let class_name = self.parse_ident()?;
let mut generics = self.parse_generics()?;
// There is a special case worth noting here, as reported in issue #17904.
// If we are parsing a tuple struct it is the case that the where clause
// should follow the field list. Like so:
//
// struct Foo<T>(T) where T: Copy;
//
// If we are parsing a normal record-style struct it is the case
// that the where clause comes before the body, and after the generics.
// So if we look ahead and see a brace or a where-clause we begin
// parsing a record style struct.
//
// Otherwise if we look ahead and see a paren we parse a tuple-style
// struct.
let vdata = if self.token.is_keyword(keywords::Where) {
generics.where_clause = self.parse_where_clause()?;
if self.eat(&token::Semi) {
// If we see a: `struct Foo<T> where T: Copy;` style decl.
VariantData::Unit(ast::DUMMY_NODE_ID)
} else {
// If we see: `struct Foo<T> where T: Copy { ... }`
VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
}
// No `where` so: `struct Foo<T>;`
} else if self.eat(&token::Semi) {
VariantData::Unit(ast::DUMMY_NODE_ID)
// Record-style struct definition
} else if self.token == token::OpenDelim(token::Brace) {
VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
// Tuple-style struct definition with optional where-clause.
} else if self.token == token::OpenDelim(token::Paren) {
let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
generics.where_clause = self.parse_where_clause()?;
self.expect(&token::Semi)?;
body
} else {
let token_str = self.this_token_descr();
let mut err = self.fatal(&format!(
"expected `where`, `{{`, `(`, or `;` after struct name, found {}",
token_str
));
err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name");
return Err(err);
};
Ok((class_name, ItemKind::Struct(vdata, generics), None))
}
/// Parses `union Foo { ... }`.
fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
let class_name = self.parse_ident()?;
let mut generics = self.parse_generics()?;
let vdata = if self.token.is_keyword(keywords::Where) {
generics.where_clause = self.parse_where_clause()?;
VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
} else if self.token == token::OpenDelim(token::Brace) {
VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
} else {
let token_str = self.this_token_descr();
let mut err = self.fatal(&format!(
"expected `where` or `{{` after union name, found {}", token_str));
err.span_label(self.span, "expected `where` or `{` after union name");
return Err(err);
};
Ok((class_name, ItemKind::Union(vdata, generics), None))
}
fn consume_block(&mut self, delim: token::DelimToken) {
let mut brace_depth = 0;
loop {
if self.eat(&token::OpenDelim(delim)) {
brace_depth += 1;
} else if self.eat(&token::CloseDelim(delim)) {
if brace_depth == 0 {
return;
} else {
brace_depth -= 1;
continue;
}
} else if self.token == token::Eof || self.eat(&token::CloseDelim(token::NoDelim)) {
return;
} else {
self.bump();
}
}
}
fn parse_record_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
let mut fields = Vec::new();
if self.eat(&token::OpenDelim(token::Brace)) {
while self.token != token::CloseDelim(token::Brace) {
let field = self.parse_struct_decl_field().map_err(|e| {
self.recover_stmt();
e
});
match field {
Ok(field) => fields.push(field),
Err(mut err) => {
err.emit();
}
}
}
self.eat(&token::CloseDelim(token::Brace));
} else {
let token_str = self.this_token_descr();
let mut err = self.fatal(&format!(
"expected `where`, or `{{` after struct name, found {}", token_str));
err.span_label(self.span, "expected `where`, or `{` after struct name");
return Err(err);
}
Ok(fields)
}
fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
// This is the case where we find `struct Foo<T>(T) where T: Copy;`
// Unit like structs are handled in parse_item_struct function
let fields = self.parse_unspanned_seq(
&token::OpenDelim(token::Paren),
&token::CloseDelim(token::Paren),
SeqSep::trailing_allowed(token::Comma),
|p| {
let attrs = p.parse_outer_attributes()?;
let lo = p.span;
let vis = p.parse_visibility(true)?;
let ty = p.parse_ty()?;
Ok(StructField {
span: lo.to(ty.span),
vis,
ident: None,
id: ast::DUMMY_NODE_ID,
ty,
attrs,
})
})?;
Ok(fields)
}
/// Parses a structure field declaration.
fn parse_single_struct_field(&mut self,
lo: Span,
vis: Visibility,
attrs: Vec<Attribute> )
-> PResult<'a, StructField> {
let mut seen_comma: bool = false;
let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
if self.token == token::Comma {
seen_comma = true;
}
match self.token {
token::Comma => {
self.bump();
}
token::CloseDelim(token::Brace) => {}
token::DocComment(_) => {
let previous_span = self.prev_span;
let mut err = self.span_fatal_err(self.span, Error::UselessDocComment);
self.bump(); // consume the doc comment
let comma_after_doc_seen = self.eat(&token::Comma);
// `seen_comma` is always false, because we are inside doc block
// condition is here to make code more readable
if seen_comma == false && comma_after_doc_seen == true {
seen_comma = true;
}
if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
err.emit();
} else {
if seen_comma == false {
let sp = self.sess.source_map().next_point(previous_span);
err.span_suggestion(
sp,
"missing comma here",
",".into(),
Applicability::MachineApplicable
);
}
return Err(err);
}
}
_ => {
let sp = self.sess.source_map().next_point(self.prev_span);
let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}",
self.this_token_descr()));
if self.token.is_ident() {
// This is likely another field; emit the diagnostic and keep going
err.span_suggestion(
sp,
"try adding a comma",
",".into(),
Applicability::MachineApplicable,
);
err.emit();
} else {
return Err(err)
}
}
}
Ok(a_var)
}
/// Parses an element of a struct declaration.
fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
let attrs = self.parse_outer_attributes()?;
let lo = self.span;
let vis = self.parse_visibility(false)?;
self.parse_single_struct_field(lo, vis, attrs)
}
/// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`,
/// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`.
/// If the following element can't be a tuple (i.e., it's a function definition), then
/// it's not a tuple struct field), and the contents within the parentheses isn't valid,
/// so emit a proper diagnostic.
pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
maybe_whole!(self, NtVis, |x| x);
self.expected_tokens.push(TokenType::Keyword(keywords::Crate));
if self.is_crate_vis() {
self.bump(); // `crate`
return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
}
if !self.eat_keyword(keywords::Pub) {
// We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
// keyword to grab a span from for inherited visibility; an empty span at the
// beginning of the current token would seem to be the "Schelling span".
return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited))
}
let lo = self.prev_span;
if self.check(&token::OpenDelim(token::Paren)) {
// We don't `self.bump()` the `(` yet because this might be a struct definition where
// `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
// Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
// by the following tokens.
if self.look_ahead(1, |t| t.is_keyword(keywords::Crate)) {
// `pub(crate)`
self.bump(); // `(`
self.bump(); // `crate`
self.expect(&token::CloseDelim(token::Paren))?; // `)`
let vis = respan(
lo.to(self.prev_span),
VisibilityKind::Crate(CrateSugar::PubCrate),
);
return Ok(vis)
} else if self.look_ahead(1, |t| t.is_keyword(keywords::In)) {
// `pub(in path)`
self.bump(); // `(`
self.bump(); // `in`
let path = self.parse_path(PathStyle::Mod)?; // `path`
self.expect(&token::CloseDelim(token::Paren))?; // `)`
let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
path: P(path),
id: ast::DUMMY_NODE_ID,
});
return Ok(vis)
} else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Super) ||
t.is_keyword(keywords::SelfLower))
{
// `pub(self)` or `pub(super)`
self.bump(); // `(`
let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
self.expect(&token::CloseDelim(token::Paren))?; // `)`
let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
path: P(path),
id: ast::DUMMY_NODE_ID,
});
return Ok(vis)
} else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct
// `pub(something) fn ...` or `struct X { pub(something) y: Z }`
self.bump(); // `(`
let msg = "incorrect visibility restriction";
let suggestion = r##"some possible visibility restrictions are:
`pub(crate)`: visible only on the current crate
`pub(super)`: visible only in the current module's parent
`pub(in path::to::module)`: visible only on the specified path"##;
let path = self.parse_path(PathStyle::Mod)?;
let sp = self.prev_span;
let help_msg = format!("make this visible only to module `{}` with `in`", path);
self.expect(&token::CloseDelim(token::Paren))?; // `)`
let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
err.help(suggestion);
err.span_suggestion(
sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
);
err.emit(); // emit diagnostic, but continue with public visibility
}
}
Ok(respan(lo, VisibilityKind::Public))
}
/// Parses defaultness (i.e., `default` or nothing).
fn parse_defaultness(&mut self) -> Defaultness {
// `pub` is included for better error messages
if self.check_keyword(keywords::Default) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Impl) ||
t.is_keyword(keywords::Const) ||
t.is_keyword(keywords::Fn) ||
t.is_keyword(keywords::Unsafe) ||
t.is_keyword(keywords::Extern) ||
t.is_keyword(keywords::Type) ||
t.is_keyword(keywords::Pub)) {
self.bump(); // `default`
Defaultness::Default
} else {
Defaultness::Final
}
}
fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
if self.eat(&token::Semi) {
let mut err = self.struct_span_err(self.prev_span, "expected item, found `;`");
err.span_suggestion_short(
self.prev_span,
"remove this semicolon",
String::new(),
Applicability::MachineApplicable,
);
if !items.is_empty() {
let previous_item = &items[items.len()-1];
let previous_item_kind_name = match previous_item.node {
// say "braced struct" because tuple-structs and
// braceless-empty-struct declarations do take a semicolon
ItemKind::Struct(..) => Some("braced struct"),
ItemKind::Enum(..) => Some("enum"),
ItemKind::Trait(..) => Some("trait"),
ItemKind::Union(..) => Some("union"),
_ => None,
};
if let Some(name) = previous_item_kind_name {
err.help(&format!("{} declarations are not followed by a semicolon", name));
}
}
err.emit();
true
} else {
false
}
}
/// Given a termination token, parses all of the items in a module.
fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
let mut items = vec![];
while let Some(item) = self.parse_item()? {
items.push(item);
self.maybe_consume_incorrect_semicolon(&items);
}
if !self.eat(term) {
let token_str = self.this_token_descr();
if !self.maybe_consume_incorrect_semicolon(&items) {
let mut err = self.fatal(&format!("expected item, found {}", token_str));
err.span_label(self.span, "expected item");
return Err(err);
}
}
let hi = if self.span.is_dummy() {
inner_lo
} else {
self.prev_span
};
Ok(ast::Mod {
inner: inner_lo.to(hi),
items,
inline: true
})
}
fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
self.expect(&token::Eq)?;
let e = self.parse_expr()?;
self.expect(&token::Semi)?;
let item = match m {
Some(m) => ItemKind::Static(ty, m, e),
None => ItemKind::Const(ty, e),
};
Ok((id, item, None))
}
/// Parse a `mod <foo> { ... }` or `mod <foo>;` item
fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
let (in_cfg, outer_attrs) = {
let mut strip_unconfigured = crate::config::StripUnconfigured {
sess: self.sess,
features: None, // don't perform gated feature checking
};
let mut outer_attrs = outer_attrs.to_owned();
strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
(!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
};
let id_span = self.span;
let id = self.parse_ident()?;
if self.eat(&token::Semi) {
if in_cfg && self.recurse_into_file_modules {
// This mod is in an external file. Let's go get it!
let ModulePathSuccess { path, directory_ownership, warn } =
self.submod_path(id, &outer_attrs, id_span)?;
let (module, mut attrs) =
self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
// Record that we fetched the mod from an external file
if warn {
let attr = Attribute {
id: attr::mk_attr_id(),
style: ast::AttrStyle::Outer,
path: ast::Path::from_ident(Ident::from_str("warn_directory_ownership")),
tokens: TokenStream::empty(),
is_sugared_doc: false,
span: syntax_pos::DUMMY_SP,
};
attr::mark_known(&attr);
attrs.push(attr);
}
Ok((id, ItemKind::Mod(module), Some(attrs)))
} else {
let placeholder = ast::Mod {
inner: syntax_pos::DUMMY_SP,
items: Vec::new(),
inline: false
};
Ok((id, ItemKind::Mod(placeholder), None))
}
} else {
let old_directory = self.directory.clone();
self.push_directory(id, &outer_attrs);
self.expect(&token::OpenDelim(token::Brace))?;
let mod_inner_lo = self.span;
let attrs = self.parse_inner_attributes()?;
let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
self.directory = old_directory;
Ok((id, ItemKind::Mod(module), Some(attrs)))
}
}
fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
if let Some(path) = attr::first_attr_value_str_by_name(attrs, "path") {
self.directory.path.to_mut().push(&path.as_str());
self.directory.ownership = DirectoryOwnership::Owned { relative: None };
} else {
// We have to push on the current module name in the case of relative
// paths in order to ensure that any additional module paths from inline
// `mod x { ... }` come after the relative extension.
//
// For example, a `mod z { ... }` inside `x/y.rs` should set the current
// directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
if let Some(ident) = relative.take() { // remove the relative offset
self.directory.path.to_mut().push(ident.as_str());
}
}
self.directory.path.to_mut().push(&id.as_str());
}
}
pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
if let Some(s) = attr::first_attr_value_str_by_name(attrs, "path") {
let s = s.as_str();
// On windows, the base path might have the form
// `\\?\foo\bar` in which case it does not tolerate
// mixed `/` and `\` separators, so canonicalize
// `/` to `\`.
#[cfg(windows)]
let s = s.replace("/", "\\");
Some(dir_path.join(s))
} else {
None
}
}
/// Returns a path to a module.
pub fn default_submod_path(
id: ast::Ident,
relative: Option<ast::Ident>,
dir_path: &Path,
source_map: &SourceMap) -> ModulePath
{
// If we're in a foo.rs file instead of a mod.rs file,
// we need to look for submodules in
// `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
// `./<id>.rs` and `./<id>/mod.rs`.
let relative_prefix_string;
let relative_prefix = if let Some(ident) = relative {
relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
&relative_prefix_string
} else {
""
};
let mod_name = id.to_string();
let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
let secondary_path_str = format!("{}{}{}mod.rs",
relative_prefix, mod_name, path::MAIN_SEPARATOR);
let default_path = dir_path.join(&default_path_str);
let secondary_path = dir_path.join(&secondary_path_str);
let default_exists = source_map.file_exists(&default_path);
let secondary_exists = source_map.file_exists(&secondary_path);
let result = match (default_exists, secondary_exists) {
(true, false) => Ok(ModulePathSuccess {
path: default_path,
directory_ownership: DirectoryOwnership::Owned {
relative: Some(id),
},
warn: false,
}),
(false, true) => Ok(ModulePathSuccess {
path: secondary_path,
directory_ownership: DirectoryOwnership::Owned {
relative: None,
},
warn: false,
}),
(false, false) => Err(Error::FileNotFoundForModule {
mod_name: mod_name.clone(),
default_path: default_path_str,
secondary_path: secondary_path_str,
dir_path: dir_path.display().to_string(),
}),
(true, true) => Err(Error::DuplicatePaths {
mod_name: mod_name.clone(),
default_path: default_path_str,
secondary_path: secondary_path_str,
}),
};
ModulePath {
name: mod_name,
path_exists: default_exists || secondary_exists,
result,
}
}
fn submod_path(&mut self,
id: ast::Ident,
outer_attrs: &[Attribute],
id_sp: Span)
-> PResult<'a, ModulePathSuccess> {
if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
return Ok(ModulePathSuccess {
directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
// All `#[path]` files are treated as though they are a `mod.rs` file.
// This means that `mod foo;` declarations inside `#[path]`-included
// files are siblings,
//
// Note that this will produce weirdness when a file named `foo.rs` is
// `#[path]` included and contains a `mod foo;` declaration.
// If you encounter this, it's your own darn fault :P
Some(_) => DirectoryOwnership::Owned { relative: None },
_ => DirectoryOwnership::UnownedViaMod(true),
},
path,
warn: false,
});
}
let relative = match self.directory.ownership {
DirectoryOwnership::Owned { relative } => relative,
DirectoryOwnership::UnownedViaBlock |
DirectoryOwnership::UnownedViaMod(_) => None,
};
let paths = Parser::default_submod_path(
id, relative, &self.directory.path, self.sess.source_map());
match self.directory.ownership {
DirectoryOwnership::Owned { .. } => {
paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
},
DirectoryOwnership::UnownedViaBlock => {
let msg =
"Cannot declare a non-inline module inside a block \
unless it has a path attribute";
let mut err = self.diagnostic().struct_span_err(id_sp, msg);
if paths.path_exists {
let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
paths.name);
err.span_note(id_sp, &msg);
}
Err(err)
}
DirectoryOwnership::UnownedViaMod(warn) => {
if warn {
if let Ok(result) = paths.result {
return Ok(ModulePathSuccess { warn: true, ..result });
}
}
let mut err = self.diagnostic().struct_span_err(id_sp,
"cannot declare a new module at this location");
if !id_sp.is_dummy() {
let src_path = self.sess.source_map().span_to_filename(id_sp);
if let FileName::Real(src_path) = src_path {
if let Some(stem) = src_path.file_stem() {
let mut dest_path = src_path.clone();
dest_path.set_file_name(stem);
dest_path.push("mod.rs");
err.span_note(id_sp,
&format!("maybe move this module `{}` to its own \
directory via `{}`", src_path.display(),
dest_path.display()));
}
}
}
if paths.path_exists {
err.span_note(id_sp,
&format!("... or maybe `use` the module `{}` instead \
of possibly redeclaring it",
paths.name));
}
Err(err)
}
}
}
/// Reads a module from a source file.
fn eval_src_mod(&mut self,
path: PathBuf,
directory_ownership: DirectoryOwnership,
name: String,
id_sp: Span)
-> PResult<'a, (ast::Mod, Vec<Attribute> )> {
let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
let mut err = String::from("circular modules: ");
let len = included_mod_stack.len();
for p in &included_mod_stack[i.. len] {
err.push_str(&p.to_string_lossy());
err.push_str(" -> ");
}
err.push_str(&path.to_string_lossy());
return Err(self.span_fatal(id_sp, &err[..]));
}
included_mod_stack.push(path.clone());
drop(included_mod_stack);
let mut p0 =
new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
p0.cfg_mods = self.cfg_mods;
let mod_inner_lo = p0.span;
let mod_attrs = p0.parse_inner_attributes()?;
let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
m0.inline = false;
self.sess.included_mod_stack.borrow_mut().pop();
Ok((m0, mod_attrs))
}
/// Parses a function declaration from a foreign module.
fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
-> PResult<'a, ForeignItem> {
self.expect_keyword(keywords::Fn)?;
let (ident, mut generics) = self.parse_fn_header()?;
let decl = self.parse_fn_decl(true)?;
generics.where_clause = self.parse_where_clause()?;
let hi = self.span;
self.expect(&token::Semi)?;
Ok(ast::ForeignItem {
ident,
attrs,
node: ForeignItemKind::Fn(decl, generics),
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
vis,
})
}
/// Parses a static item from a foreign module.
/// Assumes that the `static` keyword is already parsed.
fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
-> PResult<'a, ForeignItem> {
let mutbl = self.eat_keyword(keywords::Mut);
let ident = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
let hi = self.span;
self.expect(&token::Semi)?;
Ok(ForeignItem {
ident,
attrs,
node: ForeignItemKind::Static(ty, mutbl),
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
vis,
})
}
/// Parses a type from a foreign module.
fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
-> PResult<'a, ForeignItem> {
self.expect_keyword(keywords::Type)?;
let ident = self.parse_ident()?;
let hi = self.span;
self.expect(&token::Semi)?;
Ok(ast::ForeignItem {
ident: ident,
attrs: attrs,
node: ForeignItemKind::Ty,
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
vis: vis
})
}
fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
let error_msg = "crate name using dashes are not valid in `extern crate` statements";
let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
in the code";
let mut ident = if self.token.is_keyword(keywords::SelfLower) {
self.parse_path_segment_ident()
} else {
self.parse_ident()
}?;
let mut idents = vec![];
let mut replacement = vec![];
let mut fixed_crate_name = false;
// Accept `extern crate name-like-this` for better diagnostics
let dash = token::Token::BinOp(token::BinOpToken::Minus);
if self.token == dash { // Do not include `-` as part of the expected tokens list
while self.eat(&dash) {
fixed_crate_name = true;
replacement.push((self.prev_span, "_".to_string()));
idents.push(self.parse_ident()?);
}
}
if fixed_crate_name {
let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
let mut fixed_name = format!("{}", ident.name);
for part in idents {
fixed_name.push_str(&format!("_{}", part.name));
}
ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
let mut err = self.struct_span_err(fixed_name_sp, error_msg);
err.span_label(fixed_name_sp, "dash-separated idents are not valid");
err.multipart_suggestion(
suggestion_msg,
replacement,
Applicability::MachineApplicable,
);
err.emit();
}
Ok(ident)
}
/// Parses `extern crate` links.
///
/// # Examples
///
/// ```
/// extern crate foo;
/// extern crate bar as foo;
/// ```
fn parse_item_extern_crate(&mut self,
lo: Span,
visibility: Visibility,
attrs: Vec<Attribute>)
-> PResult<'a, P<Item>> {
// Accept `extern crate name-like-this` for better diagnostics
let orig_name = self.parse_crate_name_with_dashes()?;
let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
(rename, Some(orig_name.name))
} else {
(orig_name, None)
};
self.expect(&token::Semi)?;
let span = lo.to(self.prev_span);
Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
}
/// Parses `extern` for foreign ABIs modules.
///
/// `extern` is expected to have been
/// consumed before calling this method.
///
/// # Examples
///
/// ```ignore (only-for-syntax-highlight)
/// extern "C" {}
/// extern {}
/// ```
fn parse_item_foreign_mod(&mut self,
lo: Span,
opt_abi: Option<Abi>,
visibility: Visibility,
mut attrs: Vec<Attribute>)
-> PResult<'a, P<Item>> {
self.expect(&token::OpenDelim(token::Brace))?;
let abi = opt_abi.unwrap_or(Abi::C);
attrs.extend(self.parse_inner_attributes()?);
let mut foreign_items = vec![];
while !self.eat(&token::CloseDelim(token::Brace)) {
foreign_items.push(self.parse_foreign_item()?);
}
let prev_span = self.prev_span;
let m = ast::ForeignMod {
abi,
items: foreign_items
};
let invalid = keywords::Invalid.ident();
Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
}
/// Parses `type Foo = Bar;`
/// or
/// `existential type Foo: Bar;`
/// or
/// `return `None``
/// without modifying the parser state.
fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
// This parses the grammar:
// Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
if self.check_keyword(keywords::Type) ||
self.check_keyword(keywords::Existential) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Type)) {
let existential = self.eat_keyword(keywords::Existential);
assert!(self.eat_keyword(keywords::Type));
Some(self.parse_existential_or_alias(existential))
} else {
None
}
}
/// Parses a type alias or existential type.
fn parse_existential_or_alias(
&mut self,
existential: bool,
) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
let ident = self.parse_ident()?;
let mut tps = self.parse_generics()?;
tps.where_clause = self.parse_where_clause()?;
let alias = if existential {
self.expect(&token::Colon)?;
let bounds = self.parse_generic_bounds(None)?;
AliasKind::Existential(bounds)
} else {
self.expect(&token::Eq)?;
let ty = self.parse_ty()?;
AliasKind::Weak(ty)
};
self.expect(&token::Semi)?;
Ok((ident, alias, tps))
}
/// Parses the part of an enum declaration following the `{`.
fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
let mut variants = Vec::new();
let mut all_nullary = true;
let mut any_disr = vec![];
while self.token != token::CloseDelim(token::Brace) {
let variant_attrs = self.parse_outer_attributes()?;
let vlo = self.span;
let struct_def;
let mut disr_expr = None;
let ident = self.parse_ident()?;
if self.check(&token::OpenDelim(token::Brace)) {
// Parse a struct variant.
all_nullary = false;
struct_def = VariantData::Struct(self.parse_record_struct_body()?,
ast::DUMMY_NODE_ID);
} else if self.check(&token::OpenDelim(token::Paren)) {
all_nullary = false;
struct_def = VariantData::Tuple(self.parse_tuple_struct_body()?,
ast::DUMMY_NODE_ID);
} else if self.eat(&token::Eq) {
disr_expr = Some(AnonConst {
id: ast::DUMMY_NODE_ID,
value: self.parse_expr()?,
});
if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) {
any_disr.push(sp);
}
struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
} else {
struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
}
let vr = ast::Variant_ {
ident,
attrs: variant_attrs,
data: struct_def,
disr_expr,
};
variants.push(respan(vlo.to(self.prev_span), vr));
if !self.eat(&token::Comma) { break; }
}
self.expect(&token::CloseDelim(token::Brace))?;
if !any_disr.is_empty() && !all_nullary {
let mut err =self.struct_span_err(
any_disr.clone(),
"discriminator values can only be used with a field-less enum",
);
for sp in any_disr {
err.span_label(sp, "only valid in field-less enums");
}
err.emit();
}
Ok(ast::EnumDef { variants })
}
/// Parses an enum declaration.
fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
let id = self.parse_ident()?;
let mut generics = self.parse_generics()?;
generics.where_clause = self.parse_where_clause()?;
self.expect(&token::OpenDelim(token::Brace))?;
let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
self.recover_stmt();
self.eat(&token::CloseDelim(token::Brace));
e
})?;
Ok((id, ItemKind::Enum(enum_definition, generics), None))
}
/// Parses a string as an ABI spec on an extern type or module. Consumes
/// the `extern` keyword, if one is found.
fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
match self.token {
token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => {
let sp = self.span;
self.expect_no_suffix(sp, "ABI spec", suf);
self.bump();
match abi::lookup(&s.as_str()) {
Some(abi) => Ok(Some(abi)),
None => {
let prev_span = self.prev_span;
let mut err = struct_span_err!(
self.sess.span_diagnostic,
prev_span,
E0703,
"invalid ABI: found `{}`",
s);
err.span_label(prev_span, "invalid ABI");
err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
err.emit();
Ok(None)
}
}
}
_ => Ok(None),
}
}
fn is_static_global(&mut self) -> bool {
if self.check_keyword(keywords::Static) {
// Check if this could be a closure
!self.look_ahead(1, |token| {
if token.is_keyword(keywords::Move) {
return true;
}
match *token {
token::BinOp(token::Or) | token::OrOr => true,
_ => false,
}
})
} else {
false
}
}
fn parse_item_(
&mut self,
attrs: Vec<Attribute>,
macros_allowed: bool,
attributes_allowed: bool,
) -> PResult<'a, Option<P<Item>>> {
let (ret, tokens) = self.collect_tokens(|this| {
this.parse_item_implementation(attrs, macros_allowed, attributes_allowed)
})?;
// Once we've parsed an item and recorded the tokens we got while
// parsing we may want to store `tokens` into the item we're about to
// return. Note, though, that we specifically didn't capture tokens
// related to outer attributes. The `tokens` field here may later be
// used with procedural macros to convert this item back into a token
// stream, but during expansion we may be removing attributes as we go
// along.
//
// If we've got inner attributes then the `tokens` we've got above holds
// these inner attributes. If an inner attribute is expanded we won't
// actually remove it from the token stream, so we'll just keep yielding
// it (bad!). To work around this case for now we just avoid recording
// `tokens` if we detect any inner attributes. This should help keep
// expansion correct, but we should fix this bug one day!
Ok(ret.map(|item| {
item.map(|mut i| {
if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
i.tokens = Some(tokens);
}
i
})
}))
}
/// Parses one of the items allowed by the flags.
fn parse_item_implementation(
&mut self,
attrs: Vec<Attribute>,
macros_allowed: bool,
attributes_allowed: bool,
) -> PResult<'a, Option<P<Item>>> {
maybe_whole!(self, NtItem, |item| {
let mut item = item.into_inner();
let mut attrs = attrs;
mem::swap(&mut item.attrs, &mut attrs);
item.attrs.extend(attrs);
Some(P(item))
});
let lo = self.span;
let visibility = self.parse_visibility(false)?;
if self.eat_keyword(keywords::Use) {
// USE ITEM
let item_ = ItemKind::Use(P(self.parse_use_tree()?));
self.expect(&token::Semi)?;
let span = lo.to(self.prev_span);
let item = self.mk_item(span, keywords::Invalid.ident(), item_, visibility, attrs);
return Ok(Some(item));
}
if self.eat_keyword(keywords::Extern) {
if self.eat_keyword(keywords::Crate) {
return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
}
let opt_abi = self.parse_opt_abi()?;
if self.eat_keyword(keywords::Fn) {
// EXTERN FUNCTION ITEM
let fn_span = self.prev_span;
let abi = opt_abi.unwrap_or(Abi::C);
let (ident, item_, extra_attrs) =
self.parse_item_fn(Unsafety::Normal,
IsAsync::NotAsync,
respan(fn_span, Constness::NotConst),
abi)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
} else if self.check(&token::OpenDelim(token::Brace)) {
return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
}
self.unexpected()?;
}
if self.is_static_global() {
self.bump();
// STATIC ITEM
let m = if self.eat_keyword(keywords::Mut) {
Mutability::Mutable
} else {
Mutability::Immutable
};
let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.eat_keyword(keywords::Const) {
let const_span = self.prev_span;
if self.check_keyword(keywords::Fn)
|| (self.check_keyword(keywords::Unsafe)
&& self.look_ahead(1, |t| t.is_keyword(keywords::Fn))) {
// CONST FUNCTION ITEM
let unsafety = self.parse_unsafety();
self.bump();
let (ident, item_, extra_attrs) =
self.parse_item_fn(unsafety,
IsAsync::NotAsync,
respan(const_span, Constness::Const),
Abi::Rust)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
// CONST ITEM
if self.eat_keyword(keywords::Mut) {
let prev_span = self.prev_span;
let mut err = self.diagnostic()
.struct_span_err(prev_span, "const globals cannot be mutable");
err.span_label(prev_span, "cannot be mutable");
err.span_suggestion(
const_span,
"you might want to declare a static instead",
"static".to_owned(),
Applicability::MaybeIncorrect,
);
err.emit();
}
let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
// `unsafe async fn` or `async fn`
if (
self.check_keyword(keywords::Unsafe) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Async))
) || (
self.check_keyword(keywords::Async) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
)
{
// ASYNC FUNCTION ITEM
let unsafety = self.parse_unsafety();
self.expect_keyword(keywords::Async)?;
self.expect_keyword(keywords::Fn)?;
let fn_span = self.prev_span;
let (ident, item_, extra_attrs) =
self.parse_item_fn(unsafety,
IsAsync::Async {
closure_id: ast::DUMMY_NODE_ID,
return_impl_trait_id: ast::DUMMY_NODE_ID,
},
respan(fn_span, Constness::NotConst),
Abi::Rust)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.check_keyword(keywords::Unsafe) &&
(self.look_ahead(1, |t| t.is_keyword(keywords::Trait)) ||
self.look_ahead(1, |t| t.is_keyword(keywords::Auto)))
{
// UNSAFE TRAIT ITEM
self.bump(); // `unsafe`
let is_auto = if self.eat_keyword(keywords::Trait) {
IsAuto::No
} else {
self.expect_keyword(keywords::Auto)?;
self.expect_keyword(keywords::Trait)?;
IsAuto::Yes
};
let (ident, item_, extra_attrs) =
self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.check_keyword(keywords::Impl) ||
self.check_keyword(keywords::Unsafe) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
self.check_keyword(keywords::Default) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
self.check_keyword(keywords::Default) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe)) {
// IMPL ITEM
let defaultness = self.parse_defaultness();
let unsafety = self.parse_unsafety();
self.expect_keyword(keywords::Impl)?;
let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
let span = lo.to(self.prev_span);
return Ok(Some(self.mk_item(span, ident, item, visibility,
maybe_append(attrs, extra_attrs))));
}
if self.check_keyword(keywords::Fn) {
// FUNCTION ITEM
self.bump();
let fn_span = self.prev_span;
let (ident, item_, extra_attrs) =
self.parse_item_fn(Unsafety::Normal,
IsAsync::NotAsync,
respan(fn_span, Constness::NotConst),
Abi::Rust)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.check_keyword(keywords::Unsafe)
&& self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
// UNSAFE FUNCTION ITEM
self.bump(); // `unsafe`
// `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
self.check(&token::OpenDelim(token::Brace));
let abi = if self.eat_keyword(keywords::Extern) {
self.parse_opt_abi()?.unwrap_or(Abi::C)
} else {
Abi::Rust
};
self.expect_keyword(keywords::Fn)?;
let fn_span = self.prev_span;
let (ident, item_, extra_attrs) =
self.parse_item_fn(Unsafety::Unsafe,
IsAsync::NotAsync,
respan(fn_span, Constness::NotConst),
abi)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.eat_keyword(keywords::Mod) {
// MODULE ITEM
let (ident, item_, extra_attrs) =
self.parse_item_mod(&attrs[..])?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if let Some(type_) = self.eat_type() {
let (ident, alias, generics) = type_?;
// TYPE ITEM
let item_ = match alias {
AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
};
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
attrs);
return Ok(Some(item));
}
if self.eat_keyword(keywords::Enum) {
// ENUM ITEM
let (ident, item_, extra_attrs) = self.parse_item_enum()?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.check_keyword(keywords::Trait)
|| (self.check_keyword(keywords::Auto)
&& self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
{
let is_auto = if self.eat_keyword(keywords::Trait) {
IsAuto::No
} else {
self.expect_keyword(keywords::Auto)?;
self.expect_keyword(keywords::Trait)?;
IsAuto::Yes
};
// TRAIT ITEM
let (ident, item_, extra_attrs) =
self.parse_item_trait(is_auto, Unsafety::Normal)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.eat_keyword(keywords::Struct) {
// STRUCT ITEM
let (ident, item_, extra_attrs) = self.parse_item_struct()?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.is_union_item() {
// UNION ITEM
self.bump();
let (ident, item_, extra_attrs) = self.parse_item_union()?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
return Ok(Some(macro_def));
}
// Verify whether we have encountered a struct or method definition where the user forgot to
// add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
if visibility.node.is_pub() &&
self.check_ident() &&
self.look_ahead(1, |t| *t != token::Not)
{
// Space between `pub` keyword and the identifier
//
// pub S {}
// ^^^ `sp` points here
let sp = self.prev_span.between(self.span);
let full_sp = self.prev_span.to(self.span);
let ident_sp = self.span;
if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
// possible public struct definition where `struct` was forgotten
let ident = self.parse_ident().unwrap();
let msg = format!("add `struct` here to parse `{}` as a public struct",
ident);
let mut err = self.diagnostic()
.struct_span_err(sp, "missing `struct` for struct definition");
err.span_suggestion_short(
sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
);
return Err(err);
} else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
let ident = self.parse_ident().unwrap();
self.bump(); // `(`
let kw_name = if let Ok(Some(_)) = self.parse_self_arg() {
"method"
} else {
"function"
};
self.consume_block(token::Paren);
let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
self.bump(); // `{`
("fn", kw_name, false)
} else if self.check(&token::OpenDelim(token::Brace)) {
self.bump(); // `{`
("fn", kw_name, false)
} else if self.check(&token::Colon) {
let kw = "struct";
(kw, kw, false)
} else {
("fn` or `struct", "function or struct", true)
};
self.consume_block(token::Brace);
let msg = format!("missing `{}` for {} definition", kw, kw_name);
let mut err = self.diagnostic().struct_span_err(sp, &msg);
if !ambiguous {
let suggestion = format!("add `{}` here to parse `{}` as a public {}",
kw,
ident,
kw_name);
err.span_suggestion_short(
sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
);
} else {
if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) {
err.span_suggestion(
full_sp,
"if you meant to call a macro, try",
format!("{}!", snippet),
// this is the `ambiguous` conditional branch
Applicability::MaybeIncorrect
);
} else {
err.help("if you meant to call a macro, remove the `pub` \
and add a trailing `!` after the identifier");
}
}
return Err(err);
} else if self.look_ahead(1, |t| *t == token::Lt) {
let ident = self.parse_ident().unwrap();
self.eat_to_tokens(&[&token::Gt]);
self.bump(); // `>`
let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
if let Ok(Some(_)) = self.parse_self_arg() {
("fn", "method", false)
} else {
("fn", "function", false)
}
} else if self.check(&token::OpenDelim(token::Brace)) {
("struct", "struct", false)
} else {
("fn` or `struct", "function or struct", true)
};
let msg = format!("missing `{}` for {} definition", kw, kw_name);
let mut err = self.diagnostic().struct_span_err(sp, &msg);
if !ambiguous {
err.span_suggestion_short(
sp,
&format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
format!(" {} ", kw),
Applicability::MachineApplicable,
);
}
return Err(err);
}
}
self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
}
/// Parses a foreign item.
crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> {
maybe_whole!(self, NtForeignItem, |ni| ni);
let attrs = self.parse_outer_attributes()?;
let lo = self.span;
let visibility = self.parse_visibility(false)?;
// FOREIGN STATIC ITEM
// Treat `const` as `static` for error recovery, but don't add it to expected tokens.
if self.check_keyword(keywords::Static) || self.token.is_keyword(keywords::Const) {
if self.token.is_keyword(keywords::Const) {
self.diagnostic()
.struct_span_err(self.span, "extern items cannot be `const`")
.span_suggestion(
self.span,
"try using a static value",
"static".to_owned(),
Applicability::MachineApplicable
).emit();
}
self.bump(); // `static` or `const`
return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
}
// FOREIGN FUNCTION ITEM
if self.check_keyword(keywords::Fn) {
return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?);
}
// FOREIGN TYPE ITEM
if self.check_keyword(keywords::Type) {
return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
}
match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
Some(mac) => {
Ok(
ForeignItem {
ident: keywords::Invalid.ident(),
span: lo.to(self.prev_span),
id: ast::DUMMY_NODE_ID,
attrs,
vis: visibility,
node: ForeignItemKind::Macro(mac),
}
)
}
None => {
if !attrs.is_empty() {
self.expected_item_err(&attrs)?;
}
self.unexpected()
}
}
}
/// This is the fall-through for parsing items.
fn parse_macro_use_or_failure(
&mut self,
attrs: Vec<Attribute> ,
macros_allowed: bool,
attributes_allowed: bool,
lo: Span,
visibility: Visibility
) -> PResult<'a, Option<P<Item>>> {
if macros_allowed && self.token.is_path_start() {
// MACRO INVOCATION ITEM
let prev_span = self.prev_span;
self.complain_if_pub_macro(&visibility.node, prev_span);
let mac_lo = self.span;
// item macro.
let pth = self.parse_path(PathStyle::Mod)?;
self.expect(&token::Not)?;
// a 'special' identifier (like what `macro_rules!` uses)
// is optional. We should eventually unify invoc syntax
// and remove this.
let id = if self.token.is_ident() {
self.parse_ident()?
} else {
keywords::Invalid.ident() // no special identifier
};
// eat a matched-delimiter token tree:
let (delim, tts) = self.expect_delimited_token_tree()?;
if delim != MacDelimiter::Brace {
if !self.eat(&token::Semi) {
self.span_err(self.prev_span,
"macros that expand to items must either \
be surrounded with braces or followed by \
a semicolon");
}
}
let hi = self.prev_span;
let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
return Ok(Some(item));
}
// FAILURE TO PARSE ITEM
match visibility.node {
VisibilityKind::Inherited => {}
_ => {
return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
}
}
if !attributes_allowed && !attrs.is_empty() {
self.expected_item_err(&attrs)?;
}
Ok(None)
}
/// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
at_end: &mut bool) -> PResult<'a, Option<Mac>>
{
if self.token.is_path_start() {
let prev_span = self.prev_span;
let lo = self.span;
let pth = self.parse_path(PathStyle::Mod)?;
if pth.segments.len() == 1 {
if !self.eat(&token::Not) {
return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
}
} else {
self.expect(&token::Not)?;
}
if let Some(vis) = vis {
self.complain_if_pub_macro(&vis.node, prev_span);
}
*at_end = true;
// eat a matched-delimiter token tree:
let (delim, tts) = self.expect_delimited_token_tree()?;
if delim != MacDelimiter::Brace {
self.expect(&token::Semi)?;
}
Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
} else {
Ok(None)
}
}
fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)>
where F: FnOnce(&mut Self) -> PResult<'a, R>
{
// Record all tokens we parse when parsing this item.
let mut tokens = Vec::new();
let prev_collecting = match self.token_cursor.frame.last_token {
LastToken::Collecting(ref mut list) => {
Some(mem::replace(list, Vec::new()))
}
LastToken::Was(ref mut last) => {
tokens.extend(last.take());
None
}
};
self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
let prev = self.token_cursor.stack.len();
let ret = f(self);
let last_token = if self.token_cursor.stack.len() == prev {
&mut self.token_cursor.frame.last_token
} else {
&mut self.token_cursor.stack[prev].last_token
};
// Pull out the tokens that we've collected from the call to `f` above.
let mut collected_tokens = match *last_token {
LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
LastToken::Was(_) => panic!("our vector went away?"),
};
// If we're not at EOF our current token wasn't actually consumed by
// `f`, but it'll still be in our list that we pulled out. In that case
// put it back.
let extra_token = if self.token != token::Eof {
collected_tokens.pop()
} else {
None
};
// If we were previously collecting tokens, then this was a recursive
// call. In that case we need to record all the tokens we collected in
// our parent list as well. To do that we push a clone of our stream
// onto the previous list.
match prev_collecting {
Some(mut list) => {
list.extend(collected_tokens.iter().cloned());
list.extend(extra_token);
*last_token = LastToken::Collecting(list);
}
None => {
*last_token = LastToken::Was(extra_token);
}
}
Ok((ret?, TokenStream::new(collected_tokens)))
}
pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
let attrs = self.parse_outer_attributes()?;
self.parse_item_(attrs, true, false)
}
/// `::{` or `::*`
fn is_import_coupler(&mut self) -> bool {
self.check(&token::ModSep) &&
self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
*t == token::BinOp(token::Star))
}
/// Parses a `UseTree`.
///
/// ```
/// USE_TREE = [`::`] `*` |
/// [`::`] `{` USE_TREE_LIST `}` |
/// PATH `::` `*` |
/// PATH `::` `{` USE_TREE_LIST `}` |
/// PATH [`as` IDENT]
/// ```
fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
let lo = self.span;
let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
let kind = if self.check(&token::OpenDelim(token::Brace)) ||
self.check(&token::BinOp(token::Star)) ||
self.is_import_coupler() {
// `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
let mod_sep_ctxt = self.span.ctxt();
if self.eat(&token::ModSep) {
prefix.segments.push(
PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))
);
}
if self.eat(&token::BinOp(token::Star)) {
UseTreeKind::Glob
} else {
UseTreeKind::Nested(self.parse_use_tree_list()?)
}
} else {
// `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
prefix = self.parse_path(PathStyle::Mod)?;
if self.eat(&token::ModSep) {
if self.eat(&token::BinOp(token::Star)) {
UseTreeKind::Glob
} else {
UseTreeKind::Nested(self.parse_use_tree_list()?)
}
} else {
UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
}
};
Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
}
/// Parses a `UseTreeKind::Nested(list)`.
///
/// ```
/// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
/// ```
fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
&token::CloseDelim(token::Brace),
SeqSep::trailing_allowed(token::Comma), |this| {
Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
})
}
fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
if self.eat_keyword(keywords::As) {
self.parse_ident_or_underscore().map(Some)
} else {
Ok(None)
}
}
/// Parses a source module as a crate. This is the main entry point for the parser.
pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
let lo = self.span;
let krate = Ok(ast::Crate {
attrs: self.parse_inner_attributes()?,
module: self.parse_mod_items(&token::Eof, lo)?,
span: lo.to(self.span),
});
emit_unclosed_delims(&self.unclosed_delims, self.diagnostic());
self.unclosed_delims.clear();
krate
}
pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
let ret = match self.token {
token::Literal(token::Str_(s), suf) => (s, ast::StrStyle::Cooked, suf),
token::Literal(token::StrRaw(s, n), suf) => (s, ast::StrStyle::Raw(n), suf),
_ => return None
};
self.bump();
Some(ret)
}
pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
match self.parse_optional_str() {
Some((s, style, suf)) => {
let sp = self.prev_span;
self.expect_no_suffix(sp, "string literal", suf);
Ok((s, style))
}
_ => {
let msg = "expected string literal";
let mut err = self.fatal(msg);
err.span_label(self.span, msg);
Err(err)
}
}
}
}
pub fn emit_unclosed_delims(unclosed_delims: &[UnmatchedBrace], handler: &errors::Handler) {
for unmatched in unclosed_delims {
let mut err = handler.struct_span_err(unmatched.found_span, &format!(
"incorrect close delimiter: `{}`",
pprust::token_to_string(&token::Token::CloseDelim(unmatched.found_delim)),
));
err.span_label(unmatched.found_span, "incorrect close delimiter");
if let Some(sp) = unmatched.candidate_span {
err.span_label(sp, "close delimiter possibly meant for this");
}
if let Some(sp) = unmatched.unclosed_span {
err.span_label(sp, "un-closed delimiter");
}
err.emit();
}
}
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