Remove `TypeSuper{Foldable,Visitable}` impls for `Region`.
These traits exist so that folders/visitors can recurse into types of interest: binders, types, regions, predicates, and consts. But `Region` is non-recursive and cannot contain other types of interest, so its methods in these traits are trivial.
This commit inlines and removes those trivial methods.
r? `@compiler-errors`
Remove `remap_env_constness` in queries
This removes some of the complexities with const traits. #88119 used to be caused by this but was fixed by `param_env = param_env.without_const()`.
Don't `use rustc_hir as ast`(!)
It makes for confusing code.
This was introduced in a large commit in #67886 that rearranged a lot of `use` statements. I suspect it was an accident.
suggest lifetime for closure parameter type when mismatch
This is a draft PR, will add test cases later and be ready for review.
This PR fixes https://github.com/rust-lang/rust/issues/105675 by adding a diagnostics suggestion. Also a partial fix to https://github.com/rust-lang/rust/issues/105528.
The following code will have a compile error now:
```
fn const_if_unit(input: bool) -> impl for<'a> FnOnce(&'a ()) -> usize {
let x = |_| 1;
x
}
```
Before this PR:
```
error[E0308]: mismatched types
--> src/lib.rs:3:5
|
3 | x
| ^ one type is more general than the other
|
= note: expected trait `for<'a> FnOnce<(&'a (),)>`
found trait `FnOnce<(&(),)>`
note: this closure does not fulfill the lifetime requirements
--> src/lib.rs:2:13
|
2 | let x = |_| 1;
| ^^^
error: implementation of `FnOnce` is not general enough
--> src/lib.rs:3:5
|
3 | x
| ^ implementation of `FnOnce` is not general enough
|
= note: closure with signature `fn(&'2 ()) -> usize` must implement `FnOnce<(&'1 (),)>`, for any lifetime `'1`...
= note: ...but it actually implements `FnOnce<(&'2 (),)>`, for some specific lifetime `'2`
For more information about this error, try `rustc --explain E0308`.
error: could not compile `rust-test` due to 2 previous errors
```
After this PR:
```
error[E0308]: mismatched types
--> src/lib.rs:3:5
|
3 | x
| ^ one type is more general than the other
|
= note: expected trait `for<'a> FnOnce<(&'a (),)>`
found trait `FnOnce<(&(),)>`
note: this closure does not fulfill the lifetime requirements
--> src/lib.rs:2:13
|
2 | let x = |_| 1;
| ^^^
help: consider changing the type of the closure parameters
|
2 | let x = |_: &_| 1;
| ~~~~~~~
error: implementation of `FnOnce` is not general enough
--> src/lib.rs:3:5
|
3 | x
| ^ implementation of `FnOnce` is not general enough
|
= note: closure with signature `fn(&'2 ()) -> usize` must implement `FnOnce<(&'1 (),)>`, for any lifetime `'1`...
= note: ...but it actually implements `FnOnce<(&'2 (),)>`, for some specific lifetime `'2`
For more information about this error, try `rustc --explain E0308`.
error: could not compile `rust-test` due to 2 previous errors
```
After applying the suggestion, it compiles. The suggestion might not always be correct as the generation procedure of that suggestion is quite simple...
These traits exist so that folders/visitors can recurse into types of
interest: binders, types, regions, predicates, and consts. But `Region`
is non-recursive and cannot contain other types of interest, so its
methods in these traits are trivial.
This commit inlines and removes those trivial methods.
explicit `adt_dtorck_constraint` for `ManuallyDrop`
the only reason we didn't add outlives requirements when dropping `ManuallyDrop` was a fast-path in `trivial_dropck_outlives`. Explicitly acknowledge that fast-path in `adt_dtorck_constraint`
Do not attempt to commute comparison and cast to codegen discriminants
The general algorithm to compute a discriminant is:
```
relative_tag = tag - niche_start
is_niche = relative_tag <= (ule) relative_max
discr = if is_niche {
cast(relative_tag) + niche_variants.start()
} else {
untagged_variant
}
```
We have an optimization branch which attempts to merge the addition and the subtraction by commuting them with the cast. We currently get this optimization wrong.
This PR takes the easiest and safest way: remove the optimization, and let LLVM handle it. (Perf may not agree with that course of action 😅)
There may be a less invasive solution, but I don't have the necessary knowledge of LLVM semantics to find it. Cranelift has the same optimization, which should be handled similarly.
cc `@nikic` and `@bjorn3` if you have a better solution.
Fixes https://github.com/rust-lang/rust/issues/110128
Reformulate `point_at_expr_source_of_inferred_type` to be more accurate
Be more accurate when deducing where along the several usages of a binding it is constrained to be some type that is incompatible with an expectation.
This also renames the method to `note_source_of_type_mismatch_constraint` because I prefer that name, though I guess I can revert that. (Also drive-by rename `note_result_coercion` -> `suggest_coercing_result_via_try_operator`, because it's suggesting, not noting!)
This PR is (probably?) best reviewed per commit, but it does regress a bit only to fix it later on, so it could also be reviewed as a whole if that makes the final results more clear.
r? `@estebank`
Add a stable MIR way to get the main function
This is useful for analysis tools that only analyze the code paths that a specific program actually goes through. Or for code generators built on top of stable MIR.
Switch to `EarlyBinder` for `impl_subject` query
Part of the work to finish https://github.com/rust-lang/rust/issues/105779.
Several queries `X` have a `bound_X` variant that wraps the output in `EarlyBinder`. This adds `EarlyBinder` to the return type of the `impl_subject` query and removes `bound_impl_subject`.
r? ```@lcnr```
Remove all but one of the spans in `BoundRegionKind::BrAnon`
There are only three places where `BoundRegionKind::BrAnon` uses `Some(span)` instead of `None`. Two of them are easy to remove, which this PR does.
r? ```@jackh726```
don't uniquify regions when canonicalizing
uniquifying causes a bunch of issues, most notably it causes `AliasEq(<?x as Trait<'a>>::Assoc, <?x as Trait<'a>>::Assoc)` to result in ambiguity because both `normalizes-to` paths result in ambiguity and substs equate should trivially succeed but doesn't because we uniquified `'a` to two different regions.
I originally added uniquification to make it easier to deal with requirement 6 from the dev-guide: https://rustc-dev-guide.rust-lang.org/solve/trait-solving.html#requirements
> ### 6. Trait solving must be (free) lifetime agnostic
>
> Trait solving during codegen should have the same result as during typeck. As we erase
> all free regions during codegen we must not rely on them during typeck. A noteworthy example
> is special behavior for `'static`.
cc https://github.com/rust-lang/rustc-dev-guide/pull/1671
Relying on regions being identical may cause ICE during MIR typeck, but even without this PR we can end up relying on that as type inference vars can resolve to types which contain an identical region. Let's land this and deal with any ICE that crop up as we go. Will look at this issue again before stabilization.
r? ```@compiler-errors```
Improve safe transmute error reporting
This patch updates the error reporting when Safe Transmute is not possible between 2 types by including the reason.
Also, fix some small bugs that occur when computing the `Answer` for transmutability.
resolve: Pre-compute non-reexport module children
Instead of repeating the same logic by walking HIR during metadata encoding.
The only difference is that we are no longer encoding `macro_rules` items, but we never currently need them as a part of this list. They can be encoded separately if this need ever arises.
`module_reexports` is also un-querified, because I don't see any reasons to make it a query, only overhead.
This patch updates the error reporting when Safe Transmute is not
possible between 2 types by including the reason.
Also, fix some small bugs that occur when computing the `Answer` for
transmutability.
