The types of any associated constants in a trait implementation must match the
types in the trait definition. This error indicates that there was a mismatch.

Here's an example of this error:

```compile_fail,E0326
trait Foo {
    const BAR: bool;
}

struct Bar;

impl Foo for Bar {
    const BAR: u32 = 5; // error, expected bool, found u32
}
```