"Internal error looking up definition" using a type alias with a where clause

[pythonesque]

I guess this just hasn't been implemented yet?

#![feature(associated_types)]

trait Foo {}

pub type Bar<T> where T: Foo = T;

fn main() {}

src/hkt.rs:5:26: 5:29 error: internal error looking up a definition
src/hkt.rs:5 pub type Bar<T> where T: Foo = T;
                                      ^~~

[ftxqxd]

Bounds aren’t supported on type aliases so I guess this is just a bug with the error message.

[tamird]

Seems to work now.

trait Foo {}

pub type Bar<T> where T: Foo = T;

fn main() {}

compiles without error.

[steveklabnik]

Agreed!

[ftxqxd]

It compiles without error, but it should probably give a warning, like the equivalent version without a where clause:

// This version gives a warning:
type Foo<T: Copy> = T; // warning: trait bounds are not (yet) enforced in type definitions

// But this equivalent version doesn’t:
type Bar<T> where T: Copy = T; // no warning

fn main() {
    let _: Bar<Box<i32>> = Box::new(1); // compiles
}

[tamird]

@P1start I mentioned this on #21903 - I think this should probably be a compile error until the enforcement is there.