…diagnostic

The instance evaluation is needed to handle intrinsics such as
`type_id` and `type_name`.

Since we now use Allocation to represent all evaluated constants,
provide a few methods to help process the data inside an allocation.

Reverts rust-lang#116530

A refactoring in rust-lang#117076 changed the `DefIdVisitorSkeleton` to avoid
calling `visit_projection_ty` for `ty::Projection` aliases, and instead
just iterate over the args - this makes sense, as `visit_projection_ty`
will indirectly visit all of the same args, but in doing so, will also
create a `TraitRef` containing the trait's `DefId`, which also gets
visited. The trait's `DefId` isn't visited when we only visit the
arguments without separating them into `TraitRef` and own args first.

Signed-off-by: David Wood <[email protected]>

- Take more things by self, not &self
- Clone more things
- Rework namespacing so we can use `ty::` in the canonicalizer

… r=lcnr

Uplift the (new solver) canonicalizer into `rustc_next_trait_solver`

Uplifts the new trait solver's canonicalizer into a new crate called `rustc_next_trait_solver`.

The crate name is literally a bikeshed-avoidance name, so let's not block this PR on that -- renames are welcome later.

There are a host of other changes that were required to make this possible:
* Expose a `ConstTy` trait to get the `Interner::Ty` from a `Interner::Const`.
* Expose some constructor methods to construct `Bound` variants. These are currently methods defined on the interner themselves, but they could be pulled into traits later.
* Expose a `IntoKind` trait to turn a `Ty`/`Const`/`Region` into their corresponding `*Kind`s.
* Some minor tweaks to other APIs in `rustc_type_ir`.

The canonicalizer code itself is best reviewed **with whitespace ignored.**

r? ``@lcnr``

fix: correct the arg for 'suggest to use associated function syntax' diagnostic

close rust-lang#118469

Add instance evaluation and methods to read an allocation in StableMIR

The instance evaluation is needed to handle intrinsics such as `type_id` and `type_name`.

Since we now use Allocation to represent all evaluated constants, provide a few methods to help process the data inside an allocation.

I've also started to add a structured way to get information about the compilation target machine. For now, I've only added information needed to process an allocation.

r? ``````@ouz-a``````

…it-trait-ref-and-args, r=TaKO8Ki

privacy: visit trait def id of projections

Fixes rust-lang#117997.

A refactoring in rust-lang#117076 changed the `DefIdVisitorSkeleton` to avoid calling `visit_projection_ty` for `ty::Projection` aliases, and instead just iterate over the args - this makes sense, as `visit_projection_ty` will indirectly visit all of the same args, but in doing so, will also create a `TraitRef` containing the trait's `DefId`, which also gets visited. The trait's `DefId` isn't visited when we only visit the arguments without separating them into `TraitRef` and own args first.

Eventually this influences the reachability set and whether a function is encoded into the metadata.

…er-errors

recurse into refs when comparing tys for diagnostics

before:
![image](https://github.com/rust-lang/rust/assets/23638587/bf6abd62-c7f3-4c09-a47e-31b6e129de19)

after:
![image](https://github.com/rust-lang/rust/assets/23638587/b704d728-ddba-4204-aebe-c07dcbbcb55c)

this diff from the test suite is also quite nice imo:
```diff
`@@` -4,8  4,8 `@@` error[E0308]: mismatched types
 LL |     debug_assert_eq!(iter.next(), Some(value));
    |                                   ^^^^^^^^^^^ expected `Option<<I as Iterator>::Item>`, found `Option<&<I as Iterator>::Item>`
    |
-   = note: expected enum `Option<<I as Iterator>::Item>`
-              found enum `Option<&<I as Iterator>::Item>`
    = note: expected enum `Option<_>`
               found enum `Option<&_>`
```

…mpiler-errors

temporarily revert "ice on ambguity in mir typeck"

Reverts rust-lang#116530 as a temporary measure to fix rust-lang#117577. That issue should be ultimately fixed by checking WF of type annotations prior to normalization, which is implemented in rust-lang#104098 but this PR is intended to be backported to beta.

r? ``@compiler-errors`` (the reviewer of the reverted PR)