Highlight conflicting param-env candidates, again
Un-reverts #98794 (i.e. reverts #99290).
The previous time I attempted to land this PR, it was because of an incremental issue (#99233). The repro instructions in the issue is no longer manifest the ICE -- I think it's because this ambiguity code was refactored (I think by `@lcnr)` to no longer store the ambiguities in the fulfillment error, but instead recompute them on the fly.
The main motivation for trying to re-land this is that it fixes#105131 by highlighting the root-cause of the issue, which is conflicting param-env candidates:
```
error[E0283]: type annotations needed: cannot satisfy `Self: Gen<'source>`
|
note: multiple `impl`s or `where` clauses satisfying `Self: Gen<'source>` found
--> $DIR/conflicting-bounds.rs:3:1
|
LL | pub trait Gen<'source> {
| ^^^^^^^^^^^^^^^^^^^^^^
...
LL | Self: for<'s> Gen<'s, Output = T>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0283`.
```
Fixes#105131.
Fixes (again) #98786
Combine `ty::Projection` and `ty::Opaque` into `ty::Alias`
Implements https://github.com/rust-lang/types-team/issues/79.
This PR consolidates `ty::Projection` and `ty::Opaque` into a single `ty::Alias`, with an `AliasKind` and `AliasTy` type (renamed from `ty::ProjectionTy`, which is the inner data of `ty::Projection`) defined as so:
```
enum AliasKind {
Projection,
Opaque,
}
struct AliasTy<'tcx> {
def_id: DefId,
substs: SubstsRef<'tcx>,
}
```
Since we don't have access to `TyCtxt` in type flags computation, and because repeatedly calling `DefKind` on the def-id is expensive, these two types are distinguished with `ty::AliasKind`, conveniently glob-imported into `ty::{Projection, Opaque}`. For example:
```diff
match ty.kind() {
- ty::Opaque(..) =>
+ ty::Alias(ty::Opaque, ..) => {}
_ => {}
}
```
This PR also consolidates match arms that treated `ty::Opaque` and `ty::Projection` identically.
r? `@ghost`
Rollup of 7 pull requests
Successful merges:
- #105147 (Allow unsafe through inline const)
- #105438 (Move some codegen-y methods from `rustc_hir_analysis::collect` -> `rustc_codegen_ssa`)
- #105464 (Support #[track_caller] on async closures)
- #105476 (Change pattern borrowing suggestions to be verbose and remove invalid suggestion)
- #105500 (Make some diagnostics not depend on the source of what they reference being available)
- #105628 (Small doc fixes)
- #105659 (Don't require owned data in `MaybeStorageLive`)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Remove previously existing fallback that tried to give a good turbofish
suggestion, `need_type_info` is already good enough.
Special case `::<Vec<_>` suggestion for `Iterator::collect`.
Point out the type of associated types in every method call of iterator chains
Partially address #105184 by pointing out the type of associated types in every method call of iterator chains:
```
note: the expression is of type `Map<std::slice::Iter<'_, {integer}>, [closure@src/test/ui/iterators/invalid-iterator-chain.rs:12:18: 12:21]>`
--> src/test/ui/iterators/invalid-iterator-chain.rs:12:14
|
10 | vec![0, 1]
| ---------- this expression has type `Vec<{integer}>`
11 | .iter()
| ------ associated type `std::iter::Iterator::Item` is `&{integer}` here
12 | .map(|x| { x; })
| ^^^^^^^^^^^^^^^ associated type `std::iter::Iterator::Item` is `()` here
```
We also reduce the number of impls we mention when any of the candidates is an "exact match". This benefits the output of cases with numerics greatly.
Outstanding work would be to provide a structured suggestion for appropriate changes, like in this case detecting the spurious `;` in the closure.
When encountering an unmet obligation that affects a method chain, like
in iterator chains where one of the links has the wrong associated
type, we point at every method call and mention their evaluated
associated type at that point to give context to the user of where
expectations diverged from the code as written.
```
note: the expression is of type `Map<std::slice::Iter<'_, {integer}>, [closure@$DIR/invalid-iterator-chain.rs:12:18: 12:21]>`
--> $DIR/invalid-iterator-chain.rs:12:14
|
LL | vec![0, 1]
| ---------- this expression has type `Vec<{integer}>`
LL | .iter()
| ------ associated type `std::iter::Iterator::Item` is `&{integer}` here
LL | .map(|x| { x; })
| ^^^^^^^^^^^^^^^ associated type `std::iter::Iterator::Item` is `()` here
```
Move some queries and methods
Each commit's title should be self-explanatory. Motivated to break up some large, general files and move queries into leaf crates.
