fix: disregard type variable expectation for if expressions
Fixes#13522
As [the comment](8142d1f606/crates/hir-ty/src/infer.rs (L1087-L1090)) on `Expectation::adjust_for_branches` explains:
> If the expected type is just a type variable, then don't use an expected type. Otherwise, we might write parts of the type when checking the 'then' block which are incompatible with the 'else' branch.
Note that we already use it in match expressions. I've added tests for them too nevertheless.
feat: Diagnose some incorrect usages of the question mark operator
Trying to figure out how the type stuff in r-a works some more, I think I am doing this correct here but I am not quite sure :)
Bump chalk
There's a bug in current chalk that prevents us from properly supporting GATs, which is supposed to be fixed in v0.86. Note the following:
- v0.86 is only going to be released next Sunday so I'll keep this PR as draft until then.
- This doesn't compile without https://github.com/rust-lang/chalk/pull/779, which I hope will be included in v0.86. I confirmed this compiles with it locally.
Two breaking changes from v0.84:
- `TypeFolder` has been split into `TypeFolder` and `FallibleTypeFolder` (https://github.com/rust-lang/chalk/pull/772)
- `ProjectionTy::self_type_parameter()` has been removed (https://github.com/rust-lang/chalk/pull/778)
Two breaking changes:
- `TypeFolder` has been split into `TypeFolder` and `FallibleTypeFolder`
- `ProjectionTy::self_type_parameter()` has been removed
fix: reorder dyn bounds on render
Fixes#13368#13192 changed the order of dyn bounds, violating the [contract](3a69435af7/crates/hir-ty/src/display.rs (L896-L901)) with `write_bounds_like_dyn_trait()` on render. The projection bounds are expected to come right after the trait bound they are accompanied with.
Although the reordering procedure can be made a bit more efficient, I opted for relying only on the [invariants](3a69435af7/crates/hir-ty/src/lower.rs (L995-L998)) currently documented in `lower_dyn_trait()`. It's not the hottest path and dyn bounds tend to be short so I believe it shouldn't hurt performance noticeably.
This commit "inverts" the order of generic parameters/arguments of an
item and its parent. This is to fulfill chalk's expectation on the
order of `Substitution` for generic associated types and it's one step
forward for their support (hopefully).
Although chalk doesn't put any constraint on the order of `Substitution`
for other items, it feels natural to get everything aligned rather than
special casing GATs.
One complication is that `TyBuilder` now demands its users to pass in
parent's `Substitution` upon construction unless it's obvious that the
the item has no parent (e.g. an ADT never has parent). All users
*should* already know the parent of the item in question, and without
this, it cannot be easily reasoned about whether we're pushing the
argument for the item or for its parent.
Quick comparison of how this commit changes `Substitution`:
```rust
trait Trait<TP, const CP: usize> {
type Type<TC, const CC: usize> = ();
fn f<TC, const CC: usize>() {}
}
```
- before this commit: `[Self, TP, CP, TC, CC]` for each trait item
- after this commit: `[TC, CC, Self, TP, CP]` for each trait item
feat: type inference for generators
This PR implements basic type inference for generator and yield expressions.
Things not included in this PR:
- Generator upvars and generator witnesses are not implemented. They are only used to determine auto trait impls, so basic type inference should be fine without them, but method resolutions with auto trait bounds may not be resolved correctly.
Open questions:
- I haven't (yet) implemented `HirDisplay` for `TyKind::Generator`, so generator types are just shown as "{{generator}}" (in tests, inlay hints, hovers, etc.), which is not really nice. How should we show them?
- I added moderate amount of stuffs to minicore. I especially didn't want to add `impl<T> Deref for &T` and `impl<T> Deref for &mut T` exclusively for tests for generators; should I move them into the test fixtures or can they be placed in minicore?
cc #4309
feat: Display the value of enum variant on hover
fixes#12955
This PR adds const eval support for enums, as well as showing their value on hover, just as consts currently have.
I developed these two things at the same time, but I've realized now that they are separate. However since the hover is just a 10 line change (not including tests), I figured I may as well put them in the same PR. Though if you want them split up into "enum const eval support" and "show enum variant value on hover", I think that's reasonable too.
Since this adds const eval support for enums this also allows consts that reference enums to have their values computed now too.
The const evaluation itself is quite rudimentary, it doesn't keep track of the actual type of the enum, but it turns out that Rust doesn't actually either, and `E::A as u8` is valid regardless of the `repr` on `E`.
It also doesn't really care about what expression the enum variant contains, it could for example be a string, despite that not being allowed, but I guess it's up to the `cargo check` diagnostics to inform of such issues anyway?
fixup: remove unnecessary `Option`
Fixup for #13223, two things:
- `normalize_projection_query()` (and consequently `HirDatabase::normalize_projection()`) never returns `None` (well, it used to when I first wrote it...), so just return `Ty` instead of `Option<Ty>`
- When chalk cannot normalize projection uniquely, `normalize_trait_assoc_type()` used to return `None` before #13223, but not anymore because of the first point. I restored the behavior so its callers work as before.
