This means `DiagCtxtInner::emit_diagnostic` can return its result
directly, rather than having to modify a local variable.

It has a single call site, and this will enable subsequent refactorings.

It results in a tiny bit of duplication (another
`self.treat_next_err_as_bug()` condition) but I think it's worth it to
get more code into the main `match`.

This will enable additional refactorings.

Note that `self.suppressed_expected_diag` is no longer set for
`ForceWarning`, which is good. Nor is `TRACK_DIAGNOSTIC` called for
`Allow`, which is also good.

Also add an assertion for the levels allowed with `has_future_breakage`.

This match is complex enough that it's a good idea to enumerate every
variant.

This also means `can_be_top_or_sub` can just be `can_be_subdiag`.

I've been experimenting with transforming the StableMIR to instrument
the code with potential UB checks. The modified body will only
be used by our analysis tool, however, constants in StableMIR must be
backed by rustc constants. Thus, I'm adding a few functions to build
constants, such as building string and other primitives.

- Replace some nested if-let with let-chains
- Tweak a match pattern to allow shorthand struct syntax
- Fuse an `is_empty` check with getting the last element
- Merge some common code that emits `MalformedAttribute` and continues
- Format `"{tool}::{name}"` in a way that's consistent with other match arms
- Replace if-let-else-panic with let-else
- Use early-exit to flatten a method body

Break type metadata identifiers tests into smaller set of tests/files,
and move CFI (and KCFI) tests to a cfi (and kcfi) subdirectory,

…ine it

…g to know the `Machine` type

…t is in fact about validation failures

…s provided by source code

…iper

Add CStr::bytes iterator

See rust-lang/libs-team#135 for an ACP.

Since rust-lang/libs-team#134 was also accepted, this type is now `core::ffi::c_str::Bytes` instead of `core::ffi::CStrBytes`.

…OSTIC-calls, r=oli-obk

Document `TRACK_DIAGNOSTIC` calls.

r? ```@cjgillot```

Create some minimal HIR for associated opaque types

`LocalDefId`s for opaque types in traits and impls are created after AST -> HIR lowering, so they don't have corresponding HIR and return their various properties through fed queries.

In this PR I also feed some core HIR-related queries for these `LocalDefId`s (which happen to be HIR owners).
As a result all `LocalDefId`s now have corresponding `HirId`s and HIR nodes, and "optional" methods like `opt_local_def_id_to_hir_id` and `opt_hir_node_by_def_id` can be removed.

Follow up to rust-lang#120206.

Make incremental sessions identity no longer depend on the crate names provided by source code

This makes incremental sessions identity no longer depend on the crate names provided by source code, implementing
rust-lang/compiler-team#726.

r? ``@oli-obk``

…smaller-files, r=compiler-errors

CFI: Break tests into smaller files

Break type metadata identifiers tests into smaller set of tests/files, and move CFI (and KCFI) tests to a cfi (and kcfi) subdirectory,

…Jung

Various cleanups around the const eval query providers

r? ```@RalfJung```

after this, working on running validation before interning starts with swapping the order of two lines of code

Add methods to create StableMIR constant

I've been experimenting with transforming the StableMIR to instrument the code with potential UB checks.

The modified body will only be used by our analysis tool, however, constants in StableMIR must be backed by rustc constants. Thus, I'm adding a few functions to build constants, such as building string and other primitives.

One question I have is whether we should create a global allocation instead for strings.

r? ``@oli-obk``

Various style improvements to `rustc_lint::levels`

While reading this file, I noticed a few opportunities to make things a little nicer:

- Replace some nested if-let with let-chains
- Tweak a match pattern to allow shorthand struct syntax
- Fuse an `is_empty` check with getting the last element
- Merge some common code that emits `MalformedAttribute` and continues
- Format `"{tool}::{name}"` in a way that's consistent with other match arms
- Replace if-let-else-panic with let-else
- Use early-exit to flatten a method body

Some of these changes cause indentation churn, so ignoring whitespace is recommended.

const-eval: organize and extend tests for required-consts

This includes some tests that are known-broken and hence disabled (due to rust-lang#107503).

r? ``@oli-obk``