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Move the missing fragment identifier checking.
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In rust-lang#95555 this was moved out of `parse_tt_inner` and `nameize` into
`compute_locs`. But the next commit will be moving `compute_locs`
outwards to a place that isn't suitable for the missing fragment
identifier checking. So this reinstates the old checking.
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@nnethercote
nnethercote committed Apr 5, 2022
1 parent 896d8f5 commit 7300bd6
Showing 1 changed file with 58 additions and 47 deletions.
105 changes: 58 additions & 47 deletions compiler/rustc_expand/src/mbe/macro_parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -131,7 +131,7 @@ enum MatcherLoc {
MetaVarDecl {
span: Span,
bind: Ident,
kind: NonterminalKind,
kind: Option<NonterminalKind>,
next_metavar: usize,
seq_depth: usize,
},
Expand Down Expand Up @@ -337,26 +337,22 @@ impl TtParser {
/// recursive. This conversion is fairly cheap and the representation is sufficiently better
/// for matching than `&[TokenTree]` that it's a clear performance win even with the overhead.
/// But it might be possible to move the conversion outwards so it only occurs once per macro.
fn compute_locs(
&mut self,
sess: &ParseSess,
matcher: &[TokenTree],
) -> Result<usize, (Span, String)> {
fn compute_locs(&mut self, sess: &ParseSess, matcher: &[TokenTree]) -> usize {
fn inner(
sess: &ParseSess,
tts: &[TokenTree],
locs: &mut Vec<MatcherLoc>,
next_metavar: &mut usize,
seq_depth: usize,
) -> Result<(), (Span, String)> {
) {
for tt in tts {
match tt {
TokenTree::Token(token) => {
locs.push(MatcherLoc::Token { token: token.clone() });
}
TokenTree::Delimited(_, delimited) => {
locs.push(MatcherLoc::Delimited);
inner(sess, &delimited.all_tts, locs, next_metavar, seq_depth)?;
inner(sess, &delimited.all_tts, locs, next_metavar, seq_depth);
}
TokenTree::Sequence(_, seq) => {
// We can't determine `idx_first_after` and construct the final
Expand All @@ -370,7 +366,7 @@ impl TtParser {
let op = seq.kleene.op;
let idx_first = locs.len();
let idx_seq = idx_first - 1;
inner(sess, &seq.tts, locs, next_metavar, seq_depth + 1)?;
inner(sess, &seq.tts, locs, next_metavar, seq_depth + 1);

if let Some(separator) = &seq.separator {
locs.push(MatcherLoc::SequenceSep { separator: separator.clone() });
Expand All @@ -389,40 +385,29 @@ impl TtParser {
};
}
&TokenTree::MetaVarDecl(span, bind, kind) => {
if let Some(kind) = kind {
locs.push(MatcherLoc::MetaVarDecl {
span,
bind,
kind,
next_metavar: *next_metavar,
seq_depth,
});
*next_metavar += 1;
} else if sess
.missing_fragment_specifiers
.borrow_mut()
.remove(&span)
.is_some()
{
// E.g. `$e` instead of `$e:expr`.
return Err((span, "missing fragment specifier".to_string()));
}
locs.push(MatcherLoc::MetaVarDecl {
span,
bind,
kind,
next_metavar: *next_metavar,
seq_depth,
});
*next_metavar += 1;
}
TokenTree::MetaVar(..) | TokenTree::MetaVarExpr(..) => unreachable!(),
}
}
Ok(())
}

self.locs.clear();
let mut next_metavar = 0;
inner(sess, matcher, &mut self.locs, &mut next_metavar, /* seq_depth */ 0)?;
inner(sess, matcher, &mut self.locs, &mut next_metavar, /* seq_depth */ 0);

// A final entry is needed for eof.
self.locs.push(MatcherLoc::Eof);

// This is the number of metavar decls.
Ok(next_metavar)
next_metavar
}

/// Process the matcher positions of `cur_mps` until it is empty. In the process, this will
Expand All @@ -434,6 +419,7 @@ impl TtParser {
/// track of through the mps generated.
fn parse_tt_inner(
&mut self,
sess: &ParseSess,
num_metavar_decls: usize,
token: &Token,
) -> Option<NamedParseResult> {
Expand Down Expand Up @@ -532,12 +518,20 @@ impl TtParser {
mp.idx = idx_first;
self.cur_mps.push(mp);
}
MatcherLoc::MetaVarDecl { kind, .. } => {
&MatcherLoc::MetaVarDecl { span, 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) {
self.bb_mps.push(mp);
if let Some(kind) = kind {
if Parser::nonterminal_may_begin_with(kind, token) {
self.bb_mps.push(mp);
}
} else {
// Both this check and the one in `nameize` are necessary, surprisingly.
if sess.missing_fragment_specifiers.borrow_mut().remove(&span).is_some() {
// E.g. `$e` instead of `$e:expr`.
return Some(Error(span, "missing fragment specifier".to_string()));
}
}
}
MatcherLoc::Eof => {
Expand All @@ -564,7 +558,7 @@ impl TtParser {
// Need to take ownership of the matches from within the `Lrc`.
Lrc::make_mut(&mut eof_mp.matches);
let matches = Lrc::try_unwrap(eof_mp.matches).unwrap().into_iter();
self.nameize(matches)
self.nameize(sess, matches)
}
EofMatcherPositions::Multiple => {
Error(token.span, "ambiguity: multiple successful parses".to_string())
Expand All @@ -588,10 +582,7 @@ impl TtParser {
parser: &mut Cow<'_, Parser<'_>>,
matcher: &[TokenTree],
) -> NamedParseResult {
let num_metavar_decls = match self.compute_locs(parser.sess, matcher) {
Ok(num_metavar_decls) => num_metavar_decls,
Err((span, msg)) => return Error(span, msg),
};
let num_metavar_decls = self.compute_locs(parser.sess, matcher);

// 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 `matcher`.
Expand All @@ -607,7 +598,7 @@ impl TtParser {

// Process `cur_mps` until either we have finished the input or we need to get some
// parsing from the black-box parser done.
if let Some(res) = self.parse_tt_inner(num_metavar_decls, &parser.token) {
if let Some(res) = self.parse_tt_inner(&parser.sess, num_metavar_decls, &parser.token) {
return res;
}

Expand Down Expand Up @@ -637,7 +628,11 @@ impl TtParser {
let mut mp = self.bb_mps.pop().unwrap();
let loc = &self.locs[mp.idx];
if let &MatcherLoc::MetaVarDecl {
span, kind, next_metavar, seq_depth, ..
span,
kind: Some(kind),
next_metavar,
seq_depth,
..
} = loc
{
// We use the span of the metavariable declaration to determine any
Expand Down Expand Up @@ -682,7 +677,9 @@ impl TtParser {
.bb_mps
.iter()
.map(|mp| match &self.locs[mp.idx] {
MatcherLoc::MetaVarDecl { bind, kind, .. } => format!("{} ('{}')", kind, bind),
MatcherLoc::MetaVarDecl { bind, kind: Some(kind), .. } => {
format!("{} ('{}')", kind, bind)
}
_ => unreachable!(),
})
.collect::<Vec<String>>()
Expand All @@ -702,16 +699,30 @@ impl TtParser {
)
}

fn nameize<I: Iterator<Item = NamedMatch>>(&self, mut res: I) -> NamedParseResult {
fn nameize<I: Iterator<Item = NamedMatch>>(
&self,
sess: &ParseSess,
mut res: I,
) -> NamedParseResult {
// Make that each metavar has _exactly one_ binding. If so, insert the binding into the
// `NamedParseResult`. Otherwise, it's an error.
let mut ret_val = FxHashMap::default();
for loc in self.locs.iter() {
if let &MatcherLoc::MetaVarDecl { span, bind, .. } = loc {
match ret_val.entry(MacroRulesNormalizedIdent::new(bind)) {
Vacant(spot) => spot.insert(res.next().unwrap()),
Occupied(..) => return Error(span, format!("duplicated bind name: {}", bind)),
};
if let &MatcherLoc::MetaVarDecl { span, bind, kind, .. } = loc {
if kind.is_some() {
match ret_val.entry(MacroRulesNormalizedIdent::new(bind)) {
Vacant(spot) => spot.insert(res.next().unwrap()),
Occupied(..) => {
return Error(span, format!("duplicated bind name: {}", bind));
}
};
} else {
// Both this check and the one in `parse_tt_inner` are necessary, surprisingly.
if sess.missing_fragment_specifiers.borrow_mut().remove(&span).is_some() {
// E.g. `$e` instead of `$e:expr`.
return Error(span, "missing fragment specifier".to_string());
}
}
}
}
Success(ret_val)
Expand Down

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