Check `xform_ret_ty` for WF in the new solver to improve method winnowing
This is a bit interesting. Method probing in the old solver is stronger than the new solver because eagerly normalizing types causes us to check their corresponding trait goals. This is important because we don't end up checking all of the where clauses of a method when method probing; just the where clauses of the impl. i.e., for:
```
impl Foo
where
WC1,
{
fn method()
where
WC2,
{}
}
```
We only check WC1 and not WC2. This is because at this point in probing the method is instantiated w/ infer vars, and checking the where clauses in WC2 will lead to cycles if we were to check them (at least that's my understanding; I could investigate changing that in general, incl. in the old solver, but I don't have much confidence that it won't lead to really bad overflows.)
This PR chooses to emulate the old solver by just checking that the return type is WF. This is theoretically stronger, but I'm not too worried about it. I think we alternatively have several approaches we can take here, though this one seems the simplest. Thoughts?
r? lcnr
Structurally resolve before matching on type of projection
Another missing structural resolve in closure upvar analysis. I think it's better to place the normalization here rather than trying to guarantee that all types returned by the expr use visitor are structurally normalized, which I don't think we do now. Thoughts?
r? lcnr
Remove the "which is required by `{root_obligation}`" post-script in
"the trait `X` is not implemented for `Y`" explanation in E0277. This
information is already conveyed in the notes explaining requirements,
making it redundant while making the text (particularly in labels)
harder to read.
```
error[E0277]: the trait bound `NotCopy: Copy` is not satisfied
--> $DIR/wf-static-type.rs:10:13
|
LL | static FOO: IsCopy<Option<NotCopy>> = IsCopy { t: None };
| ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `NotCopy`
|
= note: required for `Option<NotCopy>` to implement `Copy`
note: required by a bound in `IsCopy`
--> $DIR/wf-static-type.rs:7:17
|
LL | struct IsCopy<T:Copy> { t: T }
| ^^^^ required by this bound in `IsCopy`
```
vs the prior
```
error[E0277]: the trait bound `NotCopy: Copy` is not satisfied
--> $DIR/wf-static-type.rs:10:13
|
LL | static FOO: IsCopy<Option<NotCopy>> = IsCopy { t: None };
| ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `NotCopy`, which is required by `Option<NotCopy>: Copy`
|
= note: required for `Option<NotCopy>` to implement `Copy`
note: required by a bound in `IsCopy`
--> $DIR/wf-static-type.rs:7:17
|
LL | struct IsCopy<T:Copy> { t: T }
| ^^^^ required by this bound in `IsCopy`
```
Stop inverting expectation in normalization errors
We have some funky special case logic to invert the expectation and actual type for normalization errors depending on their cause code. IMO most of the error messages get better, except for `try {}` blocks' type expectations. I think that these need to be special cased in some other way, rather than via this hack.
Fixes#131763
Compiler & its UI tests: Rename remaining occurrences of "object safe" to "dyn compatible"
Follow-up to #130826.
Part of #130852.
1. 1st commit: Fix stupid oversights. Should've been part of #130826.
2. 2nd commit: Rename the unstable feature `object_safe_for_dispatch` to `dyn_compatible_for_dispatch`. Might not be worth the churn, you decide.
3. 3rd commit: Apply the renaming to all UI tests (contents and paths).
add caching to most type folders, rm region uniquification
Fixes the new minimization of the hang in nalgebra and nalgebra itself :3
this is a bit iffy, especially the cache in `TypeRelating`. I believe all the caches are correct, but it definitely adds some non-local complexity in places. The first commit removes region uniquification, reintroducing the ICE from https://github.com/rust-lang/trait-system-refactor-initiative/issues/27. This does not affect coherence and I would like to fix this by introducing OR-region constraints
r? `@compiler-errors`
Parallel compilation of a program can cause unexpected event sequencing.
Inform the solver when this is true so it can skip invalid asserts, then
assert replaced solutions are equal if Some
Spell out other trait diagnostic
I recently saw somebody confused about the diagnostic thinking it was suggesting to add an `as` cast. This change is longer but I think it's clearer
Harmonize using root or leaf obligation in trait error reporting
When #121826 changed the error reporting to use root obligation and not the leafmost obligation, it didn't actually make sure that all the other diagnostics helper functions used the right obligation.
Specifically, when reporting similar impl candidates we are looking for impls of the root obligation, but trying to match them against the trait ref of the leaf obligation.
This does a few other miscellaneous changes. There's a lot more clean-up that could be done here, but working with this code is really grief-inducing due to how messy it has become over the years. Someone really needs to show it love. 😓
r? ``@estebank``
Fixes#126129
