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Introduce TtParser.

Browse Source 
It currently has no state, just the three methods `parse_tt`,
`parse_tt_inner`, and `bb_items_ambiguity_error`.

This commit is large but trivial, and mostly consists of changes to the
indentation of those methods. Subsequent commits will do more.
This commit is contained in:
Nicholas Nethercote 2022-03-19 07:47:22 +11:00
parent 1bfe40d11c
commit d21b4f30c1
2 changed files with 325 additions and 306 deletions
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577
compiler/rustc_expand/src/mbe/macro_parser.rs
View File

@ -492,319 +492,334 @@ 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` and `bb_items`.
///
/// For more info about the how this happens, see the module-level doc comments and the inline
/// comments of this function.
///
/// # Parameters
///
/// - `cur_items`: the set of current items to be processed. This should be empty by the end of a
/// successful execution of this function.
/// - `next_items`: the set of newly generated items. These are used to replenish `cur_items` in
/// the function `parse`.
/// - `bb_items`: the set of items that are waiting for the black-box parser.
/// - `token`: the current token of the parser.
///
/// # Returns
///
/// `Some(result)` if everything is finished, `None` otherwise. Note that matches are kept track of
/// through the items generated.
fn parse_tt_inner<'root, 'tt>(
sess: &ParseSess,
ms: &[TokenTree],
cur_items: &mut SmallVec<[MatcherPosHandle<'root, 'tt>; 1]>,
next_items: &mut SmallVec<[MatcherPosHandle<'root, 'tt>; 1]>,
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. Only modified if
// `token == Eof`.
let mut eof_items = EofItems::None;
pub struct TtParser;
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. 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 }) => {
item.top_elts = elts;
item.idx = idx + 1;
impl TtParser {
/// Process the matcher positions of `cur_items` until it is empty. In the process, this will
/// 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.
///
/// # Parameters
///
/// - `cur_items`: the set of current items to be processed. This should be empty by the end of
/// a successful execution of this function.
/// - `next_items`: the set of newly generated items. These are used to replenish `cur_items` in
/// the function `parse`.
/// - `bb_items`: the set of items that are waiting for the black-box parser.
/// - `token`: the current token of the parser.
///
/// # Returns
///
/// `Some(result)` if everything is finished, `None` otherwise. Note that matches are kept
/// track of through the items generated.
fn parse_tt_inner<'root, 'tt>(
&self,
sess: &ParseSess,
ms: &[TokenTree],
cur_items: &mut SmallVec<[MatcherPosHandle<'root, 'tt>; 1]>,
next_items: &mut SmallVec<[MatcherPosHandle<'root, 'tt>; 1]>,
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. Only
// modified if `token == Eof`.
let mut eof_items = EofItems::None;
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. 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 }) => {
item.top_elts = elts;
item.idx = idx + 1;
}
None => break,
}
None => break,
}
}
// Get the current position of the "dot" (`idx`) in `item` and the number of token trees in
// the matcher (`len`).
let idx = item.idx;
let len = item.top_elts.len();
// Get the current position of the "dot" (`idx`) in `item` and the number of token
// trees in the matcher (`len`).
let idx = item.idx;
let len = item.top_elts.len();
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![])));
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);
}
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,
))));
}
// 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(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);
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(..))));
if idx == len {
// 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();
for idx in item.match_lo..item.match_hi {
let sub = item.matches[idx].clone();
new_pos.push_match(idx, MatchedSeq(sub));
}
new_pos.match_cur = item.match_hi;
new_pos.idx += 1;
cur_items.push(new_pos);
}
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) {
if idx == len && repetition.sep.is_some() {
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);
}
} else if repetition.seq_op != mbe::KleeneOp::ZeroOrOne {
// We don't need a separator. Move the "dot" back to the beginning of the
// matcher and try to match again UNLESS we are only allowed to have _one_
// repetition.
item.match_cur = item.match_lo;
item.idx = 0;
cur_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(..))));
if idx == len {
// 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();
for idx in item.match_lo..item.match_hi {
let sub = item.matches[idx].clone();
new_pos.push_match(idx, MatchedSeq(sub));
}
new_pos.match_cur = item.match_hi;
new_pos.idx += 1;
cur_items.push(new_pos);
}
if idx == len && repetition.sep.is_some() {
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);
}
} else if repetition.seq_op != mbe::KleeneOp::ZeroOrOne {
// We don't need a separator. Move the "dot" back to the beginning of the
// matcher and try to match again UNLESS we are only allowed to have _one_
// repetition.
item.match_cur = item.match_lo;
item.idx = 0;
cur_items.push(item);
}
} else {
// 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 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,
}
}
}
}
}
// 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) => {
let matches =
eof_item.matches.iter_mut().map(|dv| Lrc::make_mut(dv).pop().unwrap());
nameize(sess, ms, matches)
}
EofItems::Multiple => {
Error(token.span, "ambiguity: multiple successful parses".to_string())
}
EofItems::None => Failure(
Token::new(
token::Eof,
if token.span.is_dummy() { token.span } else { token.span.shrink_to_hi() },
// 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) => {
let matches =
eof_item.matches.iter_mut().map(|dv| Lrc::make_mut(dv).pop().unwrap());
nameize(sess, ms, matches)
}
EofItems::Multiple => {
Error(token.span, "ambiguity: multiple successful parses".to_string())
}
EofItems::None => Failure(
Token::new(
token::Eof,
if token.span.is_dummy() { token.span } else { token.span.shrink_to_hi() },
),
"missing tokens in macro arguments",
),
"missing tokens in macro arguments",
),
})
} else {
None
}
}
/// 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],
macro_name: Ident,
) -> NamedParseResult {
// A queue of possible matcher positions. We initialize it with the matcher position in which
// the "dot" is before the first token of the first token tree in `ms`. `parse_tt_inner` then
// processes all of these possible matcher positions and produces possible next positions into
// `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.
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`.
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.
if let Some(result) = parse_tt_inner(
parser.sess,
ms,
&mut cur_items,
&mut next_items,
&mut bb_items,
&parser.token,
) {
return result;
})
} else {
None
}
}
// `parse_tt_inner` handled all cur_items, so it's empty.
assert!(cur_items.is_empty());
/// 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(
&self,
parser: &mut Cow<'_, Parser<'_>>,
ms: &[TokenTree],
macro_name: Ident,
) -> NamedParseResult {
// A queue of possible matcher positions. We initialize it with the matcher position in
// which the "dot" is before the first token of the first token tree in `ms`.
// `parse_tt_inner` then processes all of these possible matcher positions and produces
// possible next positions into `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.
let mut initial = MatcherPos::new(ms);
let mut cur_items = smallvec![MatcherPosHandle::Ref(&mut initial)];
// 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
// parser: syntax error.
return Failure(parser.token.clone(), "no rules expected this token in macro call");
loop {
let mut next_items = SmallVec::new();
// 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.
if let Some(result) = self.parse_tt_inner(
parser.sess,
ms,
&mut cur_items,
&mut next_items,
&mut bb_items,
&parser.token,
) {
return result;
}
(_, 0) => {
// Dump all possible `next_items` into `cur_items` for the next iteration. Then
// process the next token.
cur_items.extend(next_items.drain(..));
parser.to_mut().bump();
}
// `parse_tt_inner` handled all cur_items, so it's empty.
assert!(cur_items.is_empty());
(0, 1) => {
// We need to call the black-box parser to get some nonterminal.
let mut item = bb_items.pop().unwrap();
if let TokenTree::MetaVarDecl(span, _, Some(kind)) = item.top_elts.get_tt(item.idx)
{
let match_cur = item.match_cur;
// We use the span of the metavariable declaration to determine any
// edition-specific matching behavior for non-terminals.
let nt = match parser.to_mut().parse_nonterminal(kind) {
Err(mut err) => {
err.span_label(
span,
format!("while parsing argument for this `{kind}` macro fragment"),
)
.emit();
return ErrorReported;
}
Ok(nt) => nt,
};
item.push_match(match_cur, MatchedNonterminal(Lrc::new(nt)));
item.idx += 1;
item.match_cur += 1;
} else {
unreachable!()
// 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
// parser: syntax error.
return Failure(
parser.token.clone(),
"no rules expected this token in macro call",
);
}
(_, 0) => {
// Dump all possible `next_items` into `cur_items` for the next iteration. Then
// process the next token.
cur_items.extend(next_items.drain(..));
parser.to_mut().bump();
}
(0, 1) => {
// We need to call the black-box parser to get some nonterminal.
let mut item = bb_items.pop().unwrap();
if let TokenTree::MetaVarDecl(span, _, Some(kind)) =
item.top_elts.get_tt(item.idx)
{
let match_cur = item.match_cur;
// We use the span of the metavariable declaration to determine any
// edition-specific matching behavior for non-terminals.
let nt = match parser.to_mut().parse_nonterminal(kind) {
Err(mut err) => {
err.span_label(
span,
format!(
"while parsing argument for this `{kind}` macro fragment"
),
)
.emit();
return ErrorReported;
}
Ok(nt) => nt,
};
item.push_match(match_cur, MatchedNonterminal(Lrc::new(nt)));
item.idx += 1;
item.match_cur += 1;
} else {
unreachable!()
}
cur_items.push(item);
}
(_, _) => {
// Too many possibilities!
return self.bb_items_ambiguity_error(
macro_name,
next_items,
bb_items,
parser.token.span,
);
}
cur_items.push(item);
}
(_, _) => {
// Too many possibilities!
return bb_items_ambiguity_error(
macro_name,
next_items,
bb_items,
parser.token.span,
);
}
assert!(!cur_items.is_empty());
}
}
assert!(!cur_items.is_empty());
fn bb_items_ambiguity_error<'root, 'tt>(
&self,
macro_name: Ident,
next_items: SmallVec<[MatcherPosHandle<'root, 'tt>; 1]>,
bb_items: SmallVec<[MatcherPosHandle<'root, 'tt>; 1]>,
token_span: rustc_span::Span,
) -> NamedParseResult {
let nts = bb_items
.iter()
.map(|item| match item.top_elts.get_tt(item.idx) {
TokenTree::MetaVarDecl(_, bind, Some(kind)) => {
format!("{} ('{}')", kind, bind)
}
_ => panic!(),
})
.collect::<Vec<String>>()
.join(" or ");
Error(
token_span,
format!(
"local ambiguity when calling macro `{macro_name}`: multiple parsing options: {}",
match next_items.len() {
0 => format!("built-in NTs {}.", nts),
1 => format!("built-in NTs {} or 1 other option.", nts),
n => format!("built-in NTs {} or {} other options.", nts, n),
}
),
)
}
}
fn bb_items_ambiguity_error<'root, 'tt>(
macro_name: Ident,
next_items: SmallVec<[MatcherPosHandle<'root, 'tt>; 1]>,
bb_items: SmallVec<[MatcherPosHandle<'root, 'tt>; 1]>,
token_span: rustc_span::Span,
) -> NamedParseResult {
let nts = bb_items
.iter()
.map(|item| match item.top_elts.get_tt(item.idx) {
TokenTree::MetaVarDecl(_, bind, Some(kind)) => {
format!("{} ('{}')", kind, bind)
}
_ => panic!(),
})
.collect::<Vec<String>>()
.join(" or ");
Error(
token_span,
format!(
"local ambiguity when calling macro `{macro_name}`: multiple parsing options: {}",
match next_items.len() {
0 => format!("built-in NTs {}.", nts),
1 => format!("built-in NTs {} or 1 other option.", nts),
n => format!("built-in NTs {} or {} other options.", nts, n),
}
),
)
}

54
compiler/rustc_expand/src/mbe/macro_rules.rs
View File

@ -3,8 +3,7 @@ use crate::base::{SyntaxExtension, SyntaxExtensionKind};
use crate::expand::{ensure_complete_parse, parse_ast_fragment, AstFragment, AstFragmentKind};
use crate::mbe;
use crate::mbe::macro_check;
use crate::mbe::macro_parser::parse_tt;
use crate::mbe::macro_parser::{Error, ErrorReported, Failure, Success};
use crate::mbe::macro_parser::{Error, ErrorReported, Failure, Success, TtParser};
use crate::mbe::macro_parser::{MatchedNonterminal, MatchedSeq};
use crate::mbe::transcribe::transcribe;
@ -246,6 +245,7 @@ fn generic_extension<'cx>(
// this situation.)
let parser = parser_from_cx(sess, arg.clone());
let tt_parser = TtParser;
for (i, lhs) in lhses.iter().enumerate() {
// try each arm's matchers
let lhs_tt = match *lhs {
@ -259,7 +259,7 @@ fn generic_extension<'cx>(
// are not recorded. On the first `Success(..)`ful matcher, the spans are merged.
let mut gated_spans_snapshot = mem::take(&mut *sess.gated_spans.spans.borrow_mut());
match parse_tt(&mut Cow::Borrowed(&parser), lhs_tt, name) {
match tt_parser.parse_tt(&mut Cow::Borrowed(&parser), lhs_tt, name) {
Success(named_matches) => {
// The matcher was `Success(..)`ful.
// Merge the gated spans from parsing the matcher with the pre-existing ones.
@ -352,9 +352,11 @@ fn generic_extension<'cx>(
mbe::TokenTree::Delimited(_, ref delim) => &delim.tts,
_ => continue,
};
if let Success(_) =
parse_tt(&mut Cow::Borrowed(&parser_from_cx(sess, arg.clone())), lhs_tt, name)
{
if let Success(_) = tt_parser.parse_tt(
&mut Cow::Borrowed(&parser_from_cx(sess, arg.clone())),
lhs_tt,
name,
) {
if comma_span.is_dummy() {
err.note("you might be missing a comma");
} else {
@ -447,25 +449,27 @@ pub fn compile_declarative_macro(
];
let parser = Parser::new(&sess.parse_sess, body, true, rustc_parse::MACRO_ARGUMENTS);
let argument_map = match parse_tt(&mut Cow::Borrowed(&parser), &argument_gram, def.ident) {
Success(m) => m,
Failure(token, msg) => {
let s = parse_failure_msg(&token);
let sp = token.span.substitute_dummy(def.span);
sess.parse_sess.span_diagnostic.struct_span_err(sp, &s).span_label(sp, msg).emit();
return mk_syn_ext(Box::new(macro_rules_dummy_expander));
}
Error(sp, msg) => {
sess.parse_sess
.span_diagnostic
.struct_span_err(sp.substitute_dummy(def.span), &msg)
.emit();
return mk_syn_ext(Box::new(macro_rules_dummy_expander));
}
ErrorReported => {
return mk_syn_ext(Box::new(macro_rules_dummy_expander));
}
};
let tt_parser = TtParser;
let argument_map =
match tt_parser.parse_tt(&mut Cow::Borrowed(&parser), &argument_gram, def.ident) {
Success(m) => m,
Failure(token, msg) => {
let s = parse_failure_msg(&token);
let sp = token.span.substitute_dummy(def.span);
sess.parse_sess.span_diagnostic.struct_span_err(sp, &s).span_label(sp, msg).emit();
return mk_syn_ext(Box::new(macro_rules_dummy_expander));
}
Error(sp, msg) => {
sess.parse_sess
.span_diagnostic
.struct_span_err(sp.substitute_dummy(def.span), &msg)
.emit();
return mk_syn_ext(Box::new(macro_rules_dummy_expander));
}
ErrorReported => {
return mk_syn_ext(Box::new(macro_rules_dummy_expander));
}
};
let mut valid = true;