8000 When encountering chained operators use heuristics to recover from bad turbofish by estebank · Pull Request #64909 · rust-lang/rust · GitHub
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When encountering chained operators use heuristics to recover from bad turbofish #64909

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Merged
merged 8 commits into from
Oct 6, 2019
Merged

When encountering chained operators use heuristics to recover from bad turbofish #64909

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When encountering chained operators use heuristics to recover from ba…
estebank Sep 30, 2019
6c9f298
review comments
estebank Sep 30, 2019
d7dceaa
Account for missing turbofish in paths too
estebank Sep 30, 2019
d27683a
Prove bad turbofish parser recovery in test
estebank Sep 30, 2019
dfdc369
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estebank Oct 1, 2019
f1499a8
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estebank Oct 1, 2019
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estebank Oct 3, 2019
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estebank Oct 4, 2019
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Account for missing turbofish in paths too
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@estebank
estebank committed Oct 3, 2019
commit d7dceaa0c57759d37a48b5a0aa1064b7c89f957b
47 changes: 43 additions & 4 deletions src/libsyntax/parse/diagnostics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -585,12 +585,51 @@ impl<'a> Parser<'a> {
let early_return = vec![token::Eof];
self.consume_tts(1, &modifiers[..], &early_return[..]);

if self.token.kind != token::OpenDelim(token::Paren) {
// We don't have `foo< bar >(`, so we rewind the parser and bail out.
if !&[
token::OpenDelim(token::Paren),
token::ModSep,
].contains(&self.token.kind) {
// We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
// parser and bail out.
mem::replace(self, snapshot.clone());
}
}
if self.token.kind == token::OpenDelim(token::Paren) {
if token::ModSep == self.token.kind {
// We have some certainty that this was a bad turbofish at this point.
// `foo< bar >::`
err.span_suggestion(
op_span.shrink_to_lo(),
msg,
"::".to_string(),
Applicability::MaybeIncorrect,
);

let snapshot = self.clone();

self.bump(); // `::`
// Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
match self.parse_expr() {
Ok(_) => {
// 99% certain that the suggestion is correct, continue parsing.
err.emit();
// FIXME: actually check that the two expressions in the binop are
// paths and resynthesize new fn call expression instead of using
// `ExprKind::Err` placeholder.
return Ok(Some(self.mk_expr(
lhs.span.to(self.prev_span),
ExprKind::Err,
ThinVec::new(),
)));
}
Err(mut err) => {
err.cancel();
// Not entirely sure now, but we bubble the error up with the
// suggestion.
mem::replace(self, snapshot);
return Err(err);
}
}
} else if token::OpenDelim(token::Paren) == self.token.kind {
// We have high certainty that this was a bad turbofish at this point.
// `foo< bar >(`
err.span_suggestion(
Expand All @@ -601,14 +640,14 @@ impl<'a> Parser<'a> {
);

let snapshot = self.clone();
self.bump(); // `(`

// Consume the fn call arguments.
let modifiers = vec![
(token::OpenDelim(token::Paren), 1),
(token::CloseDelim(token::Paren), -1),
];
let early_return = vec![token::Eof];
self.bump(); // `(`
self.consume_tts(1, &modifiers[..], &early_return[..]);

if self.token.kind == token::Eof {
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5 changes: 3 additions & 2 deletions src/test/ui/did_you_mean/issue-40396.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -13,9 +13,10 @@ error: chained comparison operators require parentheses
|
LL | Vec<i32>::new();
| ^^^^^
help: use `::<...>` instead of `<...>` if you meant to specify type arguments
|
= help: use `::<...>` instead of `<...>` if you meant to specify type arguments
= help: or use `(...)` if you meant to specify fn arguments
LL | Vec::<i32>::new();
| ^^

error: chained comparison operators require parentheses
--> $DIR/issue-40396.rs:12:20
Expand Down
0