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Tweak handling of "struct like start" where a struct isn't supported

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This improves the case where someone tries to write a `match` expr where the patterns have type ascription syntax. Makes them less verbose, by giving up on the first encounter in the block, and makes them more accurate by only treating them as a struct literal if successfuly parsed as such.
This commit is contained in:
Esteban Küber
2025-09-24 21:06:54 +00:00
parent 15283f6fe9
commit 43057698c1
6 changed files with 93 additions and 128 deletions
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40
compiler/rustc_parse/src/parser/diagnostics.rs
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@@ -2748,28 +2748,7 @@ impl<'a> Parser<'a> {
if token::Colon != self.token.kind {
return first_pat;
}
if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
|| !self.look_ahead(1, |token| token.is_non_reserved_ident())
{
let mut snapshot_type = self.create_snapshot_for_diagnostic();
snapshot_type.bump(); // `:`
match snapshot_type.parse_ty() {
Err(inner_err) => {
inner_err.cancel();
}
Ok(ty) => {
let Err(mut err) = self.expected_one_of_not_found(&[], &[]) else {
return first_pat;
};
err.span_label(ty.span, "specifying the type of a pattern isn't supported");
self.restore_snapshot(snapshot_type);
let span = first_pat.span.to(ty.span);
first_pat = self.mk_pat(span, PatKind::Wild);
err.emit();
}
}
return first_pat;
}
// The pattern looks like it might be a path with a `::` -> `:` typo:
// `match foo { bar:baz => {} }`
let colon_span = self.token.span;
@@ -2857,7 +2836,13 @@ impl<'a> Parser<'a> {
Applicability::MaybeIncorrect,
);
} else {
first_pat = self.mk_pat(new_span, PatKind::Wild);
first_pat = self.mk_pat(
new_span,
PatKind::Err(
self.dcx()
.span_delayed_bug(colon_span, "recovered bad path pattern"),
),
);
}
self.restore_snapshot(snapshot_pat);
}
@@ -2870,7 +2855,14 @@ impl<'a> Parser<'a> {
err.span_label(ty.span, "specifying the type of a pattern isn't supported");
self.restore_snapshot(snapshot_type);
let new_span = first_pat.span.to(ty.span);
first_pat = self.mk_pat(new_span, PatKind::Wild);
first_pat =
self.mk_pat(
new_span,
PatKind::Err(self.dcx().span_delayed_bug(
colon_span,
"recovered bad pattern with type",
)),
);
}
}
err.emit();