`trivial_bounds` lint lints on non-global associated type constraints

[lcnr]

#![feature(trivial_bounds)]

trait Trait {
    type Assoc;
}
impl<T> Trait for T {
    type Assoc = T;
}

fn foo<T>()
where
    u32: Trait<Assoc = T>,
{
}

this results in

warning: trait bound u32: Trait does not depend on any type or lifetime parameters
  --> <source>:12:10
   |
12 |     u32: Trait<Assoc = T>,
   |          ^^^^^^^^^^^^^^^^
   |
   = note: `#[warn(trivial_bounds)]` on by default

but should not, as the corresponding projection bound does reference a generic parameter (and requires this function to only be called with T = u32.