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Rollup merge of #112529 - jieyouxu:block-expr-unused-must-use, r=oli-obk

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Extend `unused_must_use` to cover block exprs

Given code like

```rust
#[must_use]
fn foo() -> i32 {
    42
}

fn warns() {
    {
        foo();
    }
}

fn does_not_warn() {
    {
        foo()
    };
}

fn main() {
    warns();
    does_not_warn();
}
```

### Before This PR

```
warning: unused return value of `foo` that must be used
 --> test.rs:8:9
  |
8 |         foo();
  |         ^^^^^
  |
  = note: `#[warn(unused_must_use)]` on by default
help: use `let _ = ...` to ignore the resulting value
  |
8 |         let _ = foo();
  |         +++++++

warning: 1 warning emitted
```

### After This PR

```
warning: unused return value of `foo` that must be used
 --> test.rs:8:9
  |
8 |         foo();
  |         ^^^^^
  |
  = note: `#[warn(unused_must_use)]` on by default
help: use `let _ = ...` to ignore the resulting value
  |
8 |         let _ = foo();
  |         +++++++

warning: unused return value of `foo` that must be used
  --> test.rs:14:9
   |
14 |         foo()
   |         ^^^^^
   |
help: use `let _ = ...` to ignore the resulting value
   |
14 |         let _ = foo();
   |         +++++++      +

warning: 2 warnings emitted
```

Fixes #104253.
This commit is contained in:
Guillaume Gomez 2023-06-15 22:04:56 +02:00 • committed by GitHub
commit d233522418
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GPG key ID: 4AEE18F83AFDEB23
19 changed files with 289 additions and 65 deletions
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53
compiler/rustc_lint/src/lints.rs
View file

@ -1555,8 +1555,29 @@ pub struct UnusedOp<'a> {
pub op: &'a str,
#[label]
pub label: Span,
#[suggestion(style = "verbose", code = "let _ = ", applicability = "maybe-incorrect")]
pub suggestion: Span,
#[subdiagnostic]
pub suggestion: UnusedOpSuggestion,
}
#[derive(Subdiagnostic)]
pub enum UnusedOpSuggestion {
#[suggestion(
lint_suggestion,
style = "verbose",
code = "let _ = ",
applicability = "maybe-incorrect"
)]
NormalExpr {
#[primary_span]
span: Span,
},
#[multipart_suggestion(lint_suggestion, style = "verbose", applicability = "maybe-incorrect")]
BlockTailExpr {
#[suggestion_part(code = "let _ = ")]
before_span: Span,
#[suggestion_part(code = ";")]
after_span: Span,
},
}
#[derive(LintDiagnostic)]
@ -1599,15 +1620,25 @@ pub struct UnusedDef<'a, 'b> {
}
#[derive(Subdiagnostic)]
#[suggestion(
lint_suggestion,
style = "verbose",
code = "let _ = ",
applicability = "maybe-incorrect"
)]
pub struct UnusedDefSuggestion {
#[primary_span]
pub span: Span,
pub enum UnusedDefSuggestion {
#[suggestion(
lint_suggestion,
style = "verbose",
code = "let _ = ",
applicability = "maybe-incorrect"
)]
NormalExpr {
#[primary_span]
span: Span,
},
#[multipart_suggestion(lint_suggestion, style = "verbose", applicability = "maybe-incorrect")]
BlockTailExpr {
#[suggestion_part(code = "let _ = ")]
before_span: Span,
#[suggestion_part(code = ";")]
after_span: Span,
},
}
// Needed because of def_path_str