error[E0119]: conflicting implementations of trait `NoOverlap` for type `W<_>`
  --> $DIR/ambiguous-fail.rs:18:1
   |
LL | impl<T: Trait> NoOverlap for T {}
   | ------------------------------ first implementation here
LL |
LL | impl<T: Trait<Assoc = u32>> NoOverlap for W<T> {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `W<_>`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0119`.