Suggest calling closure with resolved return type when appropriate #63833
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…trochenkov Suggest calling closure with resolved return type when appropriate Follow up to rust-lang#63337. CC rust-lang#63100. ``` error[E0308]: mismatched types --> $DIR/fn-or-tuple-struct-without-args.rs:46:20 | LL | let closure = || 42; | -- closure defined here LL | let _: usize = closure; | ^^^^^^^ | | | expected usize, found closure | help: use parentheses to call this closure: `closure()` | = note: expected type `usize` found type `[closure@$DIR/fn-or-tuple-struct-without-args.rs:45:19: 45:24]` ```
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Rollup of 6 pull requests Successful merges: - #62744 (Refactor `TinyList::contains` and `len` to iterate instead of recurse) - #63813 (Do not suggest `.try_into()` on `i32::from(x)`) - #63833 (Suggest calling closure with resolved return type when appropriate) - #63839 (Ensure miri can do bit ops on pointer values) - #63854 (Modifies how Arg, Arm, Field, FieldPattern and Variant are visited) - #63859 (Don't unwrap the result of `span_to_snippet`) Failed merges: r? @ghost
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☔ The latest upstream changes (presumably #63873) made this pull request unmergeable. Please resolve the merge conflicts. |
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Suggest call fn ctor passed as arg to fn with type param bounds
_Reviewer note: the relevant changes are in the second commit, the first is simple and mechanical, but verbose._
When forgetting to call a fn in an argument position to an fn that has a generic bound:
```rust
async fn foo() {}
fn bar(f: impl Future<Output=()>) {}
fn main() {
bar(foo); // <- should be `bar(foo());`
}
```
suggest calling it:
```
error[E0277]: the trait bound `fn() -> impl std::future::Future {foo}: std::future::Future` is not satisfied
--> $DIR/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:9:5
|
LL | fn bar(f: impl Future<Output=()>) {}
| --------------------------------- required by `bar`
...
LL | bar(foo);
| ^^^ the trait `std::future::Future` is not implemented for `fn() -> impl std::future::Future {foo}`
|
= help: it looks like you forgot to use parentheses to call the function: `foo()`
```
Fix #63100. Follow up to #63833 and #63337.
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Follow up to #63337. CC #63100.