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Improve handling of expr->field errors

The current message for "`->` used for field access" is the following:

```rust
error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `->`
 --> src/main.rs:2:6
  |
2 |     a->b;
  |      ^^ expected one of 8 possible tokens
```

(playground link[1])

This PR tries to address this by adding a dedicated error message and recovery. The proposed error message is:

```
error: `->` used for field access or method call
 --> ./tiny_test.rs:2:6
  |
2 |     a->b;
  |      ^^ help: try using `.` instead
  |
  = help: the `.` operator will dereference the value if needed
```

(feel free to bikeshed it as much as necessary)

[1]: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=7f8b6f4433aa7866124123575456f54e

Signed-off-by: Sasha Pourcelot <sasha.pourcelot@protonmail.com>
This commit is contained in:
Sasha Pourcelot 2024-04-20 15:52:22 +02:00
parent a61b14d15e
commit 98332c108b
8 changed files with 140 additions and 4 deletions

View file

@ -230,6 +230,10 @@ parse_expected_struct_field = expected one of `,`, `:`, or `{"}"}`, found `{$tok
parse_expected_trait_in_trait_impl_found_type = expected a trait, found type
parse_expr_rarrow_call = `->` used for field access or method call
.suggestion = try using `.` instead
.help = the `.` operator will dereference the value if needed
parse_extern_crate_name_with_dashes = crate name using dashes are not valid in `extern crate` statements
.label = dash-separated idents are not valid
.suggestion = if the original crate name uses dashes you need to use underscores in the code

View file

@ -2988,3 +2988,12 @@ pub(crate) struct AsyncImpl {
#[primary_span]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(parse_expr_rarrow_call)]
#[help]
pub(crate) struct ExprRArrowCall {
#[primary_span]
#[suggestion(style = "short", applicability = "machine-applicable", code = ".")]
pub span: Span,
}

View file

@ -979,6 +979,12 @@ impl<'a> Parser<'a> {
// we are using noexpect here because we don't expect a `.` directly after a `return`
// which could be suggested otherwise
self.eat_noexpect(&token::Dot)
} else if self.token.kind == TokenKind::RArrow && self.may_recover() {
// Recovery for `expr->suffix`.
self.bump();
let span = self.prev_token.span;
self.dcx().emit_err(errors::ExprRArrowCall { span });
true
} else {
self.eat(&token::Dot)
};