Implied bound not implied across crates

[benluelo]

I tried this code:

use crate_b::{Foo, Super, Unsatisfied};

fn foo<T: Foo>() {
   unsatisfied::<<T::FooAssoc as Super>::SuperAssoc>()
}

fn unsatisfied<B: Unsatisfied>() {}

pub mod crate_b {
    pub trait Foo {
        type FooAssoc: Bar;
    }

    pub trait Bar: Super<SuperAssoc: Bound> {}

    pub trait Super {
        type SuperAssoc;
    }

    pub trait Bound: Unsatisfied {}

    pub trait Unsatisfied {}
}

This compiles fine, however if crate_b is a separate crate instead of a local module, it errors with:

error[E0277]: the trait bound `<<T as Foo>::FooAssoc as Super>::SuperAssoc: Unsatisfied` is not satisfied
 --> src/main.rs:4:19
  |
4 |     unsatisfied::<<T::FooAssoc as Super>::SuperAssoc>()
  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Unsatisfied` is not implemented for `<<T as Foo>::FooAssoc as Super>::SuperAssoc`
  |
note: required by a bound in `unsatisfied`
 --> src/main.rs:7:19
  |
7 | fn unsatisfied<B: Unsatisfied>() {}
  |                   ^^^^^^^^^^^ required by this bound in `unsatisfied`
help: consider further restricting the associated type
  |
3 | fn foo<T: Foo>() where <<T as Foo>::FooAssoc as Super>::SuperAssoc: Unsatisfied {
  |                  ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

For more information about this error, try `rustc --explain E0277`.
error: could not compile `playground` (bin "playground") due to 1 previous error

This is not fixed by the next solver (-Znext-solver).

Meta

rustc --version --verbose:

rustc 1.79.0-nightly (1388d7a06 2024-03-20)
binary: rustc
commit-hash: 1388d7a069d872bcfe5e5dd97ef61fa0a586fac0
commit-date: 2024-03-20
host: aarch64-unknown-linux-gnu
release: 1.79.0-nightly
LLVM version: 18.1.2

[benluelo]

I was able to narrow this down even further:

use crate_b::Bar;

fn bar<B: Bar>() {}

pub mod crate_b {
    pub trait Bar: Super<SuperAssoc: Bound> {}

    pub trait Super {
        type SuperAssoc;
    }

    pub trait Bound {}
}

[compiler-errors]

🤦 yep yep makes sense i'll fix it, sorry