This allows feeding a different output type to async blocks with a
different `ImplTraitContext`.

Before, the lint did the checking for `must_use` and pretty printing the
types in a special format in one pass, causing quite complex and
untranslatable code.
Now the collection and printing is split in two. That should also make
it easier to translate or extract the type pretty printing in the
future.

Also fixes an integer overflow in the array length pluralization
calculation.

…ect unsound cases

…ence

…lally allow trait resolution to prove false things during coherence

Followup to rust-lang#103778
Sorry for the quick succession but this fixes one more building issue for Tier 3 `windows-gnullvm` that I have previously missed, and it would be nice to have it in the release.

Allow opaque types in trait impl headers and rely on coherence to reject unsound cases

r? ````@lcnr````

fixes rust-lang#99840

Refactor must_use lint into two parts

Before, the lint did the checking for `must_use` and pretty printing the types in a special format in one pass, causing quite complex and untranslatable code.
Now the collection and printing is split in two. That should also make it easier to translate or extract the type pretty printing in the future.

Also fixes an integer overflow in the array length pluralization
calculation.

fixes rust-lang#104352

Lower return type outside async block creation

This allows feeding a different output type to async blocks with a different `ImplTraitContext`. Spotted this while working on rust-lang#104321

Fix --extern library finding errors

- `crate_name` is not specified/passed to `metadata_crate_location_unknown_type`
https://github.com/rust-lang/rust/blob/c493bae0d8efd75723460ce5c371f726efa93f15/compiler/rustc_error_messages/locales/en-US/metadata.ftl#L274-L275
- `metadata_lib_filename_form` is missing `$`
- Add additional check to ensure that library is file

Testing
1. Create file `a.rs`
```rust
extern crate t;
fn main() {}
```
1. Create empty file `x`
1. Create empty directory `y`
1. Run
```sh
$ rustc -o a a.rs --extern t=x
$ rustc -o a a.rs --extern t=y
```
Both currently panic with stable.

…r=thomcc

enable fuzzy_provenance_casts lint in liballoc and libstd

r? ````@thomcc````

Bump `fd-lock` in `bootstrap` again

Followup to rust-lang#103778
Sorry for the quick succession but this fixes one more building issue for Tier 3 `windows-gnullvm` that I have previously missed, and it would be nice to have it in the release.