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Rollup merge of #111230 - zacklukem:eq-less-to-less-eq, r=compiler-errors

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add hint for =< as <=

Adds a compiler hint for when `=<` is typed instead of `<=`

Example hint:
```rust
fn foo() {
    if 1 =< 3 {
        println!("Hello, World!");
    }
}
```
```
error: expected type, found `3`
 --> main.rs:2:13
  |
2 |     if 1 =< 3 {
  |          -- ^ expected type
  |          |
  |          help: did you mean: `<=`
```

This PR only emits the suggestion if there is no space between the `=` and `<`.  This hopefully narrows the scope of when this error is emitted, however this still allows this error to be emitted in cases such as this:
```
error: expected expression, found `;`
 --> main.rs:2:18
  |
2 |     if 1 =< [i32;; 3]>::hello() {
  |          --      ^ expected expression
  |          |
  |          help: did you mean: `<=`
```

Which could be a good reason not to merge since I haven't been able to think of any other ways of narrowing the scope of this diagnostic.

closes #111128
This commit is contained in:
Matthias Krüger 2023-05-06 13:30:05 +02:00 • committed by GitHub
commit 83b29ec743
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3 changed files with 79 additions and 1 deletions
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13
compiler/rustc_parse/src/parser/expr.rs
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@ -1448,8 +1448,19 @@ impl<'a> Parser<'a> {
}
fn parse_expr_path_start(&mut self) -> PResult<'a, P<Expr>> {
let maybe_eq_tok = self.prev_token.clone();
let (qself, path) = if self.eat_lt() {
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
let lt_span = self.prev_token.span;
let (qself, path) = self.parse_qpath(PathStyle::Expr).map_err(|mut err| {
// Suggests using '<=' if there is an error parsing qpath when the previous token
// is an '=' token. Only emits suggestion if the '<' token and '=' token are
// directly adjacent (i.e. '=<')
if maybe_eq_tok.kind == TokenKind::Eq && maybe_eq_tok.span.hi() == lt_span.lo() {
let eq_lt = maybe_eq_tok.span.to(lt_span);
err.span_suggestion(eq_lt, "did you mean", "<=", Applicability::Unspecified);
}
err
})?;
(Some(qself), path)
} else {
(None, self.parse_path(PathStyle::Expr)?)