nightly feature

(Using this attribute still requires a nightly feature, this just
enables that this feature does not need to be enabled on the child crate
as well)

`#[diagnostic::on_unimplemented]`

This commit replaces those `#[rustc_on_unimplemented]` attributes with
their equivalent `#[diagnostic::on_unimplemented]` where this is
supported (So no filter or any extended option)

the corresponding feature.

`Diagnostic` has 40 methods that return `&mut Self` and could be
considered setters. Four of them have a `set_` prefix. This doesn't seem
necessary for a type that implements the builder pattern. This commit
removes the `set_` prefixes on those four methods.

It's not used, and doesn't quite fit the general pattern.

Also, `Diagnostic::downgrade_to_delayed_bug` doesn't need to return
`&mut Self` for the same reason.

- Move comments onto corresponding `Diagnostic` methods.
- Make formatting more consistent.

`create_almost_fatal` and `emit_almost_fatal` are always used instead.

These are misleading, because the mixture of `Level` and
`rustc_errors::Level` makes it look like there are two different types
involved.

It has a single call site.

Because it's redundant w.r.t. `Diagnostic::is_lint`, which is present
for every diagnostic level.

`struct_lint_level_impl` was the only place that set the `Error` field
to `true`, and it's also the only place that calls
`Diagnostic::is_lint()` to set the `is_lint` field.

By using FxIndexMap instead of FxHashMap, so that the order of visiting
of locals is deterministic.

We also need to bless
copy_propagation_arg.foo.DestinationPropagation.panic*.diff. Do not
review the diff of the diff. Instead look at the diff file before and
after this commit. Both before and after this commit, 3 statements are
replaced with nop. It's just that due to change in ordering, different
statements are replaced. But the net result is the same.

…er-errors

Add support for shell argfiles

Closes rust-lang/compiler-team#684

…den-suggest, r=davidtwco

Hide foreign `#[doc(hidden)]` paths in import suggestions

Stops the compiler from suggesting to import foreign `#[doc(hidden)]` paths.

``@rustbot`` label A-suggestion-diagnostics

…in_stdlib, r=compiler-errors

Use diagnostic namespace in stdlib

This required a minor fix to have the diagnostics shown in third party crates when the `diagnostic_namespace` feature is not enabled. See rust-lang@5d63f5d for details. I've opted for having a single PR for both changes as it's really not that much code. If it is required it should be easy to split up the change into several PR's.

r? `@compiler-errors`

…nds, r=compiler-errors

Imply outlives-bounds on lazy type aliases

Fixes rust-lang#118479.

r? types

…mpiler-errors

Cleanup error handlers: round 5

More rustc_errors cleanups. A sequel to rust-lang#119171.

r? `@compiler-errors`

…r=oli-obk

Check yield terminator's resume type in borrowck

In borrowck, we didn't check that the lifetimes of the `TerminatorKind::Yield`'s `resume_place` were actually compatible with the coroutine's signature. That means that the lifetimes were totally going unchecked. Whoops!

This PR implements this checking.

Fixes rust-lang#119564

r? types

…ulacrum

cstore: Remove unnecessary locking from `CrateMetadata`

Locks and atomics in `CrateMetadata` fields were necessary before rust-lang#107765 when `CStore` was cloneable, but now they are not necessary and can be removed after restructuring the code a bit to please borrow checker.

All remaining locked fields in `CrateMetadata` are lazily populated caches.

…ble, r=cjgillot

rustc_mir_transform: Make DestinationPropagation stable for queries

By using `FxIndexMap` instead of `FxHashMap`, so that the order of visiting of locals is deterministic.

We also need to bless
`copy_propagation_arg.foo.DestinationPropagation.panic*.diff`. Do not review the diff of the diff. Instead look at the diff files before and after this commit. Both before and after this commit, 3 statements are replaced with nop. It's just that due to change in ordering, different statements are replaced. But the net result is the same. In other words, compare this diff (before fix):
* https://github.com/rust-lang/rust/blob/090d5eac722000906cc00d991f2bf052b0e388c3/tests/mir-opt/dest-prop/copy_propagation_arg.foo.DestinationPropagation.panic-unwind.diff

With this diff (after fix):
* https://github.com/rust-lang/rust/blob/f603babd63a607e155609dc0277806e559626ea0/tests/mir-opt/dest-prop/copy_propagation_arg.foo.DestinationPropagation.panic-unwind.diff

and you can see that both before and after the fix, we replace 3 statements with `nop`s.

I find it _slightly_ surprising that the test this PR affects did not previously fail spuriously due to the indeterminism of `FxHashMap`, but I guess in can be explained with the predictability of small `FxHashMap`s with `usize` (`Local`) keys, or something along those lines.

This should fix [this](rust-lang#119252 (comment)) comment, but I wanted to make a separate PR for this fix for a simpler development and review process.

Part of rust-lang#84447 which is E-help-wanted.

r? `@cjgillot` who is reviewer for the highly related PR rust-lang#119252.