Suggest `-> impl Trait` and `-> Box<dyn Trait>` on fn that doesn't return
During development, a function could have a return type set that is a
bare trait object by accident. We already suggest using either a boxed
trait object or `impl Trait` if the return paths will allow it. We now
do so too when there are *no* return paths or they all resolve to `!`.
We still don't handle cases where the trait object is *not* the entirety
of the return type gracefully.
Closes#38376.
Check that main/start is not async
* Add new error code E0752
* Add span to hir::IsAsync::Yes
* Emit an error if main or the start function is marked as async
* Add two regression tests
This PR fixes#68523.
When the return type is `!Sized` we look for all the returned
expressions in the body to fetch their types and provide a reasonable
suggestion. The tail expression of the body is normally evaluated after
checking whether the return type is `Sized`. Changing the order of the
evaluation produces undesirable knock down effects, so we detect the
specific case that newcomers are likely to encounter ,returning a single
bare trait object, and only in that case we evaluate the tail
expression's type so that the suggestion will be accurate.
* Add new error code E0752
* Add span to hir::IsAsync::Yes
* Emit an error if main or the start function is marked as async
* Add two regression tests
Fix formatting errors and bless test outputs
* move tests to ui/async-await
fix test error text
remove span from IsAsync
Replace "rc"/"arc" lang items with Rc/Arc diagnostic items.
`Rc`/`Arc` should have no special semantics, so it seems appropriate for them to not be lang items.
r? @matthewjasper
Support `#[track_caller]` on functions in `extern "Rust" { ... }`
Fixes https://github.com/rust-lang/rust/issues/70830 which is the follow-up to @eddyb's suggestion in https://github.com/rust-lang/rust/pull/69251#discussion_r380791634 to allow `#[track_caller]` on `fn`s in FFI imports, that is, on functions in `extern "Rust" { ... }` blocks.
This requires that the other side, the FFI export, also have the `#[track_caller]` attribute. Otherwise, undefined behavior is triggered and the blame lies, as usual, with the `unsafe { ... }` block which called the FFI imported function.
After this PR, all forms of `fn` items with the right ABI (`"Rust"`) support `#[track_caller]`.
As a drive-by, the PR also hardens the check rejecting `#[naked] #[track_caller]` such that methods and other forms of `fn` items are also considered.
r? @eddyb
cc @rust-lang/lang
infer array len from pattern
closes#70529
This still errors in the following case
```rust
#![feature(const_generics)]
fn arr<const N: usize>() -> [u8; N] {
todo!()
}
fn main() {
match arr() {
[5, ..] => (),
//~^ ERROR cannot pattern-match on an array without a fixed length
[_, _] => (),
}
}
```
Considering that this should be rare and is harder to implement I would merge this PR without *fixing* the above.
Add long error code for error E0226
Added a long description message for error E0226, which previously did not exist.
As requested in issue #61137
r? @GuillaumeGomez
