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Rollup merge of #106712 - Ezrashaw:impl-ref-trait, r=estebank

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make error emitted on `impl &Trait` nicer

Fixes #106694

Turned out to be simpler than I thought, also added UI test.

Before: ([playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=9bda53271ef3a8886793cf427b8cea91))
```text
error: expected one of `:`, ``@`,` or `|`, found `)`
 --> src/main.rs:2:22
  |
2 | fn foo(_: impl &Trait) {}
  |                      ^ expected one of `:`, ``@`,` or `|`
  |
  = note: anonymous parameters are removed in the 2018 edition (see RFC 1685)
help: if this is a parameter name, give it a type
  |
2 | fn foo(_: impl Trait: &TypeName) {}
  |                ~~~~~~~~~~~~~~~~
help: if this is a type, explicitly ignore the parameter name
  |
2 | fn foo(_: impl _: &Trait) {}
  |                ++

error: expected one of `!`, `(`, `)`, `,`, `?`, `for`, `~`, lifetime, or path, found `&`
 --> src/main.rs:2:16
  |
2 | fn foo(_: impl &Trait) {}
  |               -^ expected one of 9 possible tokens
  |               |
  |               help: missing `,`

error: expected one of `!`, `(`, `,`, `=`, `>`, `?`, `for`, `~`, lifetime, or path, found `&`
 --> src/main.rs:3:11
  |
3 | fn bar<T: &Trait>(_: T) {}
  |           ^ expected one of 10 possible tokens
```

After:
```text
error: expected a trait, found type
 --> <anon>:2:16
  |
2 | fn foo(_: impl &Trait) {}
  |                -^^^^^
  |                |
  |                help: consider removing the indirection

error: expected a trait, found type
 --> <anon>:3:11
  |
3 | fn bar<T: &Trait>(_: T) {}
  |           -^^^^^
  |           |
  |           help: consider removing the indirection
```
This commit is contained in:
Matthias Krüger 2023-01-17 05:25:21 +01:00 • committed by GitHub
commit 9cda9e0ab6
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4 changed files with 155 additions and 5 deletions
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40
compiler/rustc_parse/src/parser/ty.rs
View file

@ -727,11 +727,13 @@ impl<'a> Parser<'a> {
let mut bounds = Vec::new();
let mut negative_bounds = Vec::new();
// In addition to looping while we find generic bounds:
// We continue even if we find a keyword. This is necessary for error recovery on,
// for example, `impl fn()`. The only keyword that can go after generic bounds is
// `where`, so stop if it's it.
// We also continue if we find types (not traits), again for error recovery.
while self.can_begin_bound()
// Continue even if we find a keyword.
// This is necessary for error recover on, for example, `impl fn()`.
//
// The only keyword that can go after generic bounds is `where`, so stop if it's it.
|| self.token.can_begin_type()
|| (self.token.is_reserved_ident() && !self.token.is_keyword(kw::Where))
{
if self.token.is_keyword(kw::Dyn) {
@ -938,6 +940,36 @@ impl<'a> Parser<'a> {
&& self.look_ahead(1, |tok| tok.kind == TokenKind::OpenDelim(Delimiter::Parenthesis))
&& let Some(path) = self.recover_path_from_fn()
{
path
} else if !self.token.is_path_start() && self.token.can_begin_type() {
let ty = self.parse_ty_no_plus()?;
// Instead of finding a path (a trait), we found a type.
let mut err = self.struct_span_err(ty.span, "expected a trait, found type");
// If we can recover, try to extract a path from the type. Note
// that we do not use the try operator when parsing the type because
// if it fails then we get a parser error which we don't want (we're trying
// to recover from errors, not make more).
let path = if self.may_recover()
&& matches!(ty.kind, TyKind::Ptr(..) | TyKind::Ref(..))
&& let TyKind::Path(_, path) = &ty.peel_refs().kind {
// Just get the indirection part of the type.
let span = ty.span.until(path.span);
err.span_suggestion_verbose(
span,
"consider removing the indirection",
"",
Applicability::MaybeIncorrect,
);
path.clone()
} else {
return Err(err);
};
err.emit();
path
} else {
self.parse_path(PathStyle::Type)?