Create a canonical trait query for `evaluate_obligation`
This builds on the canonical query machinery introduced in #48411 to introduce a new canonical trait query for `evaluate_obligation` in the trait selector. Also ports most callers of the original `evaluate_obligation` to the new system (except in coherence, which requires support for intercrate mode). Closes#48537.
r? @nikomatsakis
We store the obligation that caused the overflow as part of the OverflowError, and report it at the public API endpoints (rather than in the implementation internals).
drop elaboration should reveal all
This used to happen implicitly through the normalization function; but we now keep the param-env as is, which seems less surprising.
cc #49685
r? @eddyb
Treat repr(Rust) univariant fieldless enums as ZSTs
This makes all those enums be represented the same way:
```rust
enum A1 { B1 }
enum A2 { B2 = 0 }
enum A3 { B3, C3(!) }
```
Related to #15747.
Cc @rust-lang/wg-codegen @rust-lang/lang
Rollup of 4 pull requests
Successful merges:
- #50177 (mark std::str::replace(,n) as #[must_use])
- #50207 (Hash EntryKind::AssociatedConst const data)
- #50214 (Js improvements)
- #50219 (Added missing `.` in docs.)
Failed merges:
- #50229 (Add setting to go to item if there is only one result)
Allow variant discriminant initializers to refer to other initializer…
…s of the same enum
r? @eddyb
fixes the 2.4 failure of https://github.com/rust-lang/rust/issues/49765
cc @durka @retep998
Allow crate:: in local paths
Currently if you want to use `crate` locally you have to do `::crate::`. This shouldn't be necessary
(will fix up tests later)
r? @petrochenkov
Introduce compile-pass
r? @alexcrichton
The plan is to move things that cannot fail (no assert, unwrap, etc) out so we don't have to run them, and in the long term we can also stop running LLVM for them.
Out of 3215 tests...
```
Language Files Lines Code Comments Blanks
Rust 3215 119254 64688 35135 19431
```
16% of them has an empty main (which is already moved in this PR).
```
grep -rnPzl 'fn main\(\)\s*{\s*}' | xargs rg --files-without-match cfg | wc -l
547
```
And only 50% of the tests contains assertions:
```
rg -e assert -e unwrap -e expect -e panic -l | wc -l
1600
```
The remainder is likely able to get moved, but they need check by a human so I didn't touch them in PR.
cc @rust-lang/compiler
* [ ] Update documentation
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