821d50aa0c
Warn about unused expressions with closure or generator type. This follows
existing precedence of must use annotations present on `FnOnce`, `FnMut`, `Fn`
traits, which already indirectly apply to closures in some cases, e.g.,:
```rust
fn f() -> impl FnOnce() {
|| {}
}
fn main() {
// an existing warning: unused implementer of `std::ops::FnOnce` that must be used:
f();
// a new warning: unused closure that must be used:
|| {};
}
```
12 lines
290 B
Plaintext
12 lines
290 B
Plaintext
warning: unused closure that must be used
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--> $DIR/issue-1460.rs:6:5
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LL | {|i: u32| if 1 == i { }};
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| ^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: `#[warn(unused_must_use)]` on by default
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= note: closures are lazy and do nothing unless called
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warning: 1 warning emitted
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