warning: the feature `generic_associated_types` is incomplete and may not be safe to use and/or cause compiler crashes
  --> $DIR/constraint-assoc-type-suggestion.rs:3:12
   |
LL | #![feature(generic_associated_types)]
   |            ^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: `#[warn(incomplete_features)]` on by default
   = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information

error[E0308]: mismatched types
  --> $DIR/constraint-assoc-type-suggestion.rs:13:23
   |
LL |     let b: Vec<i32> = a;
   |            --------   ^ expected struct `Vec`, found associated type
   |            |
   |            expected due to this
   |
   = note:       expected struct `Vec<i32>`
           found associated type `<T as X>::Y<i32>`
help: consider constraining the associated type `<T as X>::Y<i32>` to `Vec<i32>`
   |
LL | fn f<T: X<Y<i32> = Vec<i32>>>(a: T::Y<i32>) {
   |          ^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0308`.