...of the type being matched.
This change will result in a better diagnostic for code like the following:
```rust
enum Enum {
Foo,
Bar
}
fn f(x: Enum) {
match x {
Foo => (),
Bar => ()
}
}
```
which would currently simply fail with an unreachable pattern error
on the 2nd arm.
The user is advised to either use a qualified path in the patterns
or import the variants explicitly into the scope.
This plugs a leak where resolve was treating enums defined in parent modules as
in-scope for all children modules when resolving a pattern identifier. This
eliminates the code path in resolve entirely.
If this breaks any existing code, then it indicates that the variants need to be
explicitly imported into the module.
Closes#14221
[breaking-change]
