| Age | Commit message (Collapse) | Author | Lines |
|---|
|
|
|
|
|
This reverts commit 6499c5e7fc173a3f55b7a3bd1e6a50e9edef782d, reversing
changes made to 78450d2d602b06d9b94349aaf8cece1a4acaf3a8.
|
|
This reverts commit e7cc3bddbe0d0e374d05e7003e662bba1742dbae, reversing
changes made to 734368a200904ef9c21db86c595dc04263c87be0.
|
|
by using an opaque type obligation to bubble up comparisons between opaque types and other types
Also uses proper obligation causes so that the body id works, because out of some reason nll uses body ids for logic instead of just diagnostics.
|
|
Fix #70968, partially address #66523.
|
|
Related: #66426
This commit adds handling for opaque types during inference variable
fallback. Type variables generated from the instantiatino of opaque
types now fallback to the opque type itself.
Normally, the type variable for an instantiated opaque type is either
unified with the concrete type, or with the opaque type itself (e.g when
a function returns an opaque type by calling another function).
However, it's possible for the type variable to be left completely
unconstrained. This can occur in code like this:
```rust
pub type Foo = impl Copy;
fn produce() -> Option<Foo> {
None
}
```
Here, we'll instantatiate the `Foo` in `Option<Foo>` to a fresh type
variable, but we will never unify it with anything due to the fact
that we return a `None`.
This results in the error message:
`type annotations needed: cannot resolve `_: std::marker::Copy``
pointing at `pub type Foo = impl Copy`.
This message is not only confusing, it's incorrect. When an opaque type
inference variable is completely unconstrained, we can always fall back
to using the opaque type itself. This effectively turns that particular
use of the opaque type into a non-defining use, even if it appears in a
defining scope.
|
