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Auto merge of #95067 - nnethercote:parse_tt-more-refactoring, r=petrochenkov

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Still more refactoring of `parse_tt`

r? `@petrochenkov`
This commit is contained in:
bors 2022-03-18 12:34:05 +00:00
commit a8adf7685a
1 changed files with 124 additions and 142 deletions
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288
compiler/rustc_expand/src/mbe/macro_parser.rs
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@ -74,7 +74,7 @@ crate use NamedMatch::*;
crate use ParseResult::*;
use TokenTreeOrTokenTreeSlice::*;
use crate::mbe::{self, TokenTree};
use crate::mbe::{self, DelimSpan, SequenceRepetition, TokenTree};
use rustc_ast::token::{self, DocComment, Nonterminal, Token};
use rustc_parse::parser::Parser;
@ -93,12 +93,12 @@ use std::ops::{Deref, DerefMut};
// To avoid costly uniqueness checks, we require that `MatchSeq` always has a nonempty body.
/// Either a sequence of token trees or a single one. This is used as the representation of the
/// sequence of tokens that make up a matcher.
/// Either a slice of token trees or a single one. This is used as the representation of the
/// token trees that make up a matcher.
#[derive(Clone)]
enum TokenTreeOrTokenTreeSlice<'tt> {
Tt(TokenTree),
TtSeq(&'tt [TokenTree]),
TtSlice(&'tt [TokenTree]),
}
impl<'tt> TokenTreeOrTokenTreeSlice<'tt> {
@ -106,7 +106,7 @@ impl<'tt> TokenTreeOrTokenTreeSlice<'tt> {
/// will not recursively descend into subtrees).
fn len(&self) -> usize {
match *self {
TtSeq(ref v) => v.len(),
TtSlice(ref v) => v.len(),
Tt(ref tt) => tt.len(),
}
}
@ -114,7 +114,7 @@ impl<'tt> TokenTreeOrTokenTreeSlice<'tt> {
/// The `index`-th token tree of `self`.
fn get_tt(&self, index: usize) -> TokenTree {
match *self {
TtSeq(ref v) => v[index].clone(),
TtSlice(ref v) => v[index].clone(),
Tt(ref tt) => tt.get_tt(index),
}
}
@ -154,7 +154,7 @@ type NamedMatchVec = SmallVec<[NamedMatch; 4]>;
/// lifetime. By separating `'tt` from `'root`, we can show that.
#[derive(Clone)]
struct MatcherPos<'root, 'tt> {
/// The token or sequence of tokens that make up the matcher. `elts` is short for "elements".
/// The token or slice of tokens that make up the matcher. `elts` is short for "elements".
top_elts: TokenTreeOrTokenTreeSlice<'tt>,
/// The position of the "dot" in this matcher
@ -203,13 +203,24 @@ struct MatcherPos<'root, 'tt> {
rustc_data_structures::static_assert_size!(MatcherPos<'_, '_>, 240);
impl<'root, 'tt> MatcherPos<'root, 'tt> {
/// `len` `Vec`s (initially shared and empty) that will store matches of metavars.
fn create_matches(len: usize) -> Box<[Lrc<NamedMatchVec>]> {
if len == 0 {
vec![]
} else {
let empty_matches = Lrc::new(SmallVec::new());
vec![empty_matches; len]
}
.into_boxed_slice()
}
/// Generates the top-level matcher position in which the "dot" is before the first token of
/// the matcher `ms`.
fn new(ms: &'tt [TokenTree]) -> Self {
let match_idx_hi = count_names(ms);
MatcherPos {
// Start with the top level matcher given to us.
top_elts: TtSeq(ms),
top_elts: TtSlice(ms),
// The "dot" is before the first token of the matcher.
idx: 0,
@ -217,7 +228,7 @@ impl<'root, 'tt> MatcherPos<'root, 'tt> {
// Initialize `matches` to a bunch of empty `Vec`s -- one for each metavar in
// `top_elts`. `match_lo` for `top_elts` is 0 and `match_hi` is `match_idx_hi`.
// `match_cur` is 0 since we haven't actually matched anything yet.
matches: create_matches(match_idx_hi),
matches: Self::create_matches(match_idx_hi),
match_lo: 0,
match_cur: 0,
match_hi: match_idx_hi,
@ -230,6 +241,27 @@ impl<'root, 'tt> MatcherPos<'root, 'tt> {
}
}
fn repetition(
up: MatcherPosHandle<'root, 'tt>,
sp: DelimSpan,
seq: Lrc<SequenceRepetition>,
) -> Self {
MatcherPos {
stack: smallvec![],
idx: 0,
matches: Self::create_matches(up.matches.len()),
match_lo: up.match_cur,
match_cur: up.match_cur,
match_hi: up.match_cur + seq.num_captures,
repetition: Some(MatcherPosRepetition {
up,
sep: seq.separator.clone(),
seq_op: seq.kleene.op,
}),
top_elts: Tt(TokenTree::Sequence(sp, seq)),
}
}
/// Adds `m` as a named match for the `idx`-th metavar.
fn push_match(&mut self, idx: usize, m: NamedMatch) {
let matches = Lrc::make_mut(&mut self.matches[idx]);
@ -336,17 +368,6 @@ pub(super) fn count_names(ms: &[TokenTree]) -> usize {
})
}
/// `len` `Vec`s (initially shared and empty) that will store matches of metavars.
fn create_matches(len: usize) -> Box<[Lrc<NamedMatchVec>]> {
if len == 0 {
vec![]
} else {
let empty_matches = Lrc::new(SmallVec::new());
vec![empty_matches; len]
}
.into_boxed_slice()
}
/// `NamedMatch` is a pattern-match result for a single `token::MATCH_NONTERMINAL`:
/// so it is associated with a single ident in a parse, and all
/// `MatchedNonterminal`s in the `NamedMatch` have the same non-terminal type
@ -401,7 +422,7 @@ crate enum NamedMatch {
MatchedNonterminal(Lrc<Nonterminal>),
}
/// Takes a sequence of token trees `ms` representing a matcher which successfully matched input
/// Takes a slice of token trees `ms` representing a matcher which successfully matched input
/// and an iterator of items that matched input and produces a `NamedParseResult`.
fn nameize<I: Iterator<Item = NamedMatch>>(
sess: &ParseSess,
@ -472,7 +493,7 @@ fn token_name_eq(t1: &Token, t2: &Token) -> bool {
}
/// Process the matcher positions of `cur_items` until it is empty. In the process, this will
/// produce more items in `next_items`, `eof_items`, and `bb_items`.
/// produce more items in `next_items` and `bb_items`.
///
/// For more info about the how this happens, see the module-level doc comments and the inline
/// comments of this function.
@ -498,14 +519,14 @@ fn parse_tt_inner<'root, 'tt>(
bb_items: &mut SmallVec<[MatcherPosHandle<'root, 'tt>; 1]>,
token: &Token,
) -> Option<NamedParseResult> {
// Matcher positions that would be valid if the macro invocation was over now
// Matcher positions that would be valid if the macro invocation was over now. Only modified if
// `token == Eof`.
let mut eof_items = EofItems::None;
// Pop items from `cur_items` until it is empty.
while let Some(mut item) = cur_items.pop() {
// When unzipped trees end, remove them. This corresponds to backtracking out of a
// delimited submatcher into which we already descended. In backtracking out again, we need
// to advance the "dot" past the delimiters in the outer matcher.
// delimited submatcher into which we already descended. When backtracking out again, we
// need to advance the "dot" past the delimiters in the outer matcher.
while item.idx >= item.top_elts.len() {
match item.stack.pop() {
Some(MatcherTtFrame { elts, idx }) => {
@ -521,43 +542,97 @@ fn parse_tt_inner<'root, 'tt>(
let idx = item.idx;
let len = item.top_elts.len();
// If `idx >= len`, then we are at or past the end of the matcher of `item`.
if idx >= len {
// We are repeating iff there is a parent. If the matcher is inside of a repetition,
// then we could be at the end of a sequence or at the beginning of the next
// repetition.
if let Some(repetition) = &item.repetition {
if idx < len {
// We are in the middle of a matcher. Compare the matcher's current tt against `token`.
match item.top_elts.get_tt(idx) {
TokenTree::Sequence(sp, seq) => {
let op = seq.kleene.op;
if op == mbe::KleeneOp::ZeroOrMore || op == mbe::KleeneOp::ZeroOrOne {
// Allow for the possibility of zero matches of this sequence.
let mut new_item = item.clone();
new_item.match_cur += seq.num_captures;
new_item.idx += 1;
for idx in item.match_cur..item.match_cur + seq.num_captures {
new_item.push_match(idx, MatchedSeq(Lrc::new(smallvec![])));
}
cur_items.push(new_item);
}
// Allow for the possibility of one or more matches of this sequence.
cur_items.push(MatcherPosHandle::Box(Box::new(MatcherPos::repetition(
item, sp, seq,
))));
}
TokenTree::MetaVarDecl(span, _, None) => {
// E.g. `$e` instead of `$e:expr`.
if sess.missing_fragment_specifiers.borrow_mut().remove(&span).is_some() {
return Some(Error(span, "missing fragment specifier".to_string()));
}
}
TokenTree::MetaVarDecl(_, _, Some(kind)) => {
// Built-in nonterminals never start with these tokens, so we can eliminate
// them from consideration.
//
// We use the span of the metavariable declaration to determine any
// edition-specific matching behavior for non-terminals.
if Parser::nonterminal_may_begin_with(kind, token) {
bb_items.push(item);
}
}
seq @ (TokenTree::Delimited(..)
| TokenTree::Token(Token { kind: DocComment(..), .. })) => {
// To descend into a delimited submatcher or a doc comment, we push the current
// matcher onto a stack and push a new item containing the submatcher onto
// `cur_items`.
//
// At the beginning of the loop, if we reach the end of the delimited
// submatcher, we pop the stack to backtrack out of the descent.
let lower_elts = mem::replace(&mut item.top_elts, Tt(seq));
let idx = item.idx;
item.stack.push(MatcherTtFrame { elts: lower_elts, idx });
item.idx = 0;
cur_items.push(item);
}
TokenTree::Token(t) => {
// If the token matches, we can just advance the parser. Otherwise, this match
// hash failed, there is nothing to do, and hopefully another item in
// `cur_items` will match.
if token_name_eq(&t, token) {
item.idx += 1;
next_items.push(item);
}
}
// These cannot appear in a matcher.
TokenTree::MetaVar(..) | TokenTree::MetaVarExpr(..) => unreachable!(),
}
} else if let Some(repetition) = &item.repetition {
// We are past the end of a repetition.
debug_assert!(idx <= len + 1);
debug_assert!(matches!(item.top_elts, Tt(TokenTree::Sequence(..))));
// At this point, regardless of whether there is a separator, we should add all
// matches from the complete repetition of the sequence to the shared, top-level
// `matches` list (actually, `up.matches`, which could itself not be the top-level,
// but anyway...). Moreover, we add another item to `cur_items` in which the "dot"
// is at the end of the `up` matcher. This ensures that the "dot" in the `up`
// matcher is also advanced sufficiently.
//
// NOTE: removing the condition `idx == len` allows trailing separators.
if idx == len {
// Get the `up` matcher
// Add all matches from the sequence to `up`, and move the "dot" past the
// repetition in `up`. This allows for the case where the sequence matching is
// finished.
let mut new_pos = repetition.up.clone();
// Add matches from this repetition to the `matches` of `up`
for idx in item.match_lo..item.match_hi {
let sub = item.matches[idx].clone();
new_pos.push_match(idx, MatchedSeq(sub));
}
// Move the "dot" past the repetition in `up`
new_pos.match_cur = item.match_hi;
new_pos.idx += 1;
cur_items.push(new_pos);
}
// Check if we need a separator.
if idx == len && repetition.sep.is_some() {
// We have a separator, and it is the current token. We can advance past the
// separator token.
if repetition.sep.as_ref().map_or(false, |sep| token_name_eq(token, sep)) {
// The matcher has a separator, and it matches the current token. We can
// advance past the separator token.
item.idx += 1;
next_items.push(item);
}
@ -570,107 +645,19 @@ fn parse_tt_inner<'root, 'tt>(
cur_items.push(item);
}
} else {
// If we are not in a repetition, then being at the end of a matcher means that we
// have reached the potential end of the input.
// We are past the end of the matcher, and not in a repetition. Look for end of input.
debug_assert_eq!(idx, len);
if *token == token::Eof {
eof_items = match eof_items {
EofItems::None => EofItems::One(item),
EofItems::One(_) | EofItems::Multiple => EofItems::Multiple,
}
}
} else {
// We are in the middle of a matcher. Look at what token in the matcher we are trying
// to match the current token (`token`) against. Depending on that, we may generate new
// items.
match item.top_elts.get_tt(idx) {
// Need to descend into a sequence
TokenTree::Sequence(sp, seq) => {
// Examine the case where there are 0 matches of this sequence. We are
// implicitly disallowing OneOrMore from having 0 matches here. Thus, that will
// result in a "no rules expected token" error by virtue of this matcher not
// working.
if seq.kleene.op == mbe::KleeneOp::ZeroOrMore
|| seq.kleene.op == mbe::KleeneOp::ZeroOrOne
{
let mut new_item = item.clone();
new_item.match_cur += seq.num_captures;
new_item.idx += 1;
for idx in item.match_cur..item.match_cur + seq.num_captures {
new_item.push_match(idx, MatchedSeq(Lrc::new(smallvec![])));
}
cur_items.push(new_item);
}
let matches = create_matches(item.matches.len());
cur_items.push(MatcherPosHandle::Box(Box::new(MatcherPos {
stack: smallvec![],
idx: 0,
matches,
match_lo: item.match_cur,
match_cur: item.match_cur,
match_hi: item.match_cur + seq.num_captures,
repetition: Some(MatcherPosRepetition {
up: item,
sep: seq.separator.clone(),
seq_op: seq.kleene.op,
}),
top_elts: Tt(TokenTree::Sequence(sp, seq)),
})));
}
// We need to match a metavar (but the identifier is invalid)... this is an error
TokenTree::MetaVarDecl(span, _, None) => {
if sess.missing_fragment_specifiers.borrow_mut().remove(&span).is_some() {
return Some(Error(span, "missing fragment specifier".to_string()));
}
}
// We need to match a metavar with a valid ident... call out to the black-box
// parser by adding an item to `bb_items`.
TokenTree::MetaVarDecl(_, _, Some(kind)) => {
// Built-in nonterminals never start with these tokens, so we can eliminate
// them from consideration.
//
// We use the span of the metavariable declaration to determine any
// edition-specific matching behavior for non-terminals.
if Parser::nonterminal_may_begin_with(kind, token) {
bb_items.push(item);
}
}
// We need to descend into a delimited submatcher or a doc comment. To do this, we
// push the current matcher onto a stack and push a new item containing the
// submatcher onto `cur_items`.
//
// At the beginning of the loop, if we reach the end of the delimited submatcher,
// we pop the stack to backtrack out of the descent.
seq @ (TokenTree::Delimited(..)
| TokenTree::Token(Token { kind: DocComment(..), .. })) => {
let lower_elts = mem::replace(&mut item.top_elts, Tt(seq));
let idx = item.idx;
item.stack.push(MatcherTtFrame { elts: lower_elts, idx });
item.idx = 0;
cur_items.push(item);
}
// We just matched a normal token. We can just advance the parser.
TokenTree::Token(t) if token_name_eq(&t, token) => {
item.idx += 1;
next_items.push(item);
}
// There was another token that was not `token`... This means we can't add any
// rules. NOTE that this is not necessarily an error unless _all_ items in
// `cur_items` end up doing this. There may still be some other matchers that do
// end up working out.
TokenTree::Token(..) => {}
TokenTree::MetaVar(..) | TokenTree::MetaVarExpr(..) => unreachable!(),
}
}
}
// If we reached the EOF, check that there is EXACTLY ONE possible matcher. Otherwise,
// either the parse is ambiguous (which should never happen) or there is a syntax error.
// If we reached the end of input, check that there is EXACTLY ONE possible matcher. Otherwise,
// either the parse is ambiguous (which is an error) or there is a syntax error.
if *token == token::Eof {
Some(match eof_items {
EofItems::One(mut eof_item) => {
@ -694,8 +681,8 @@ fn parse_tt_inner<'root, 'tt>(
}
}
/// Use the given sequence of token trees (`ms`) as a matcher. Match the token
/// stream from the given `parser` against it and return the match.
/// Use the given slice of token trees (`ms`) as a matcher. Match the token stream from the given
/// `parser` against it and return the match.
pub(super) fn parse_tt(
parser: &mut Cow<'_, Parser<'_>>,
ms: &[TokenTree],
@ -707,20 +694,19 @@ pub(super) fn parse_tt(
// `next_items`. After some post-processing, the contents of `next_items` replenish `cur_items`
// and we start over again.
//
// This MatcherPos instance is allocated on the stack. All others -- and
// there are frequently *no* others! -- are allocated on the heap.
// This MatcherPos instance is allocated on the stack. All others -- and there are frequently
// *no* others! -- are allocated on the heap.
let mut initial = MatcherPos::new(ms);
let mut cur_items = smallvec![MatcherPosHandle::Ref(&mut initial)];
loop {
let mut next_items = SmallVec::new();
// Matcher positions black-box parsed by parser.rs (`parser`)
// Matcher positions black-box parsed by `Parser`.
let mut bb_items = SmallVec::new();
// Process `cur_items` until either we have finished the input or we need to get some
// parsing from the black-box parser done. The result is that `next_items` will contain a
// bunch of possible next matcher positions in `next_items`.
// parsing from the black-box parser done.
if let Some(result) = parse_tt_inner(
parser.sess,
ms,
@ -735,10 +721,7 @@ pub(super) fn parse_tt(
// `parse_tt_inner` handled all cur_items, so it's empty.
assert!(cur_items.is_empty());
// We need to do some post processing after the `parse_tt_inner`.
//
// Error messages here could be improved with links to original rules.
match (next_items.len(), bb_items.len()) {
(0, 0) => {
// There are no possible next positions AND we aren't waiting for the black-box
@ -782,8 +765,7 @@ pub(super) fn parse_tt(
}
(_, _) => {
// We need to call the black-box parser to get some nonterminal, but something is
// wrong.
// Too many possibilities!
return bb_items_ambiguity_error(
macro_name,
next_items,