const initializer is not considered a "defining use" for type_alias_impl_trait

[Nemo157]

I tried this code:

#![feature(type_alias_impl_trait)]

pub type Foo = impl std::fmt::Debug;
pub const FOO: Foo = 5usize;

I expected to see this happen: successful compilation

Instead, this happened:

error[E0308]: mismatched types
 --> src/lib.rs:4:22
  |
3 | pub type Foo = impl std::fmt::Debug;
  |                -------------------- the expected opaque type
4 | pub const FOO: Foo = 5usize;
  |                      ^^^^^^ expected opaque type, found `usize`
  |
  = note: expected opaque type `impl Debug`
                    found type `usize`

error: could not find defining uses
 --> src/lib.rs:3:16
  |
3 | pub type Foo = impl std::fmt::Debug;
  |                ^^^^^^^^^^^^^^^^^^^^

Meta

1.49.0-nightly (2020-10-12 8dae8cdcc8fa879cea6a)

[Nemo157]

@rustbot modify labels: +requires-nightly, +A-impl-trait, +F-type_alias_impl_trait

[jackh726]

This works now with min_type_alias_impl_trait, but also requires impl_trait_in_bindings

[jplatte]

min_type_alias_impl_trait has been removed in #87501, what does that mean for this issue?

[jackh726]

This is something we probably want type_alias_impl_trait to do, so this can stay open.

Also, not sure why I said this requires impl_trait_in_bindings...

[oli-obk]

This has been fixed in #94081 which also has tests that pass with it