error: at least one trait must be specified
  --> $DIR/generic_underconstrained.rs:6:40
   |
LL | type Underconstrained<T: Trait> = impl 'static;
   |                                        ^^^^^^^

error[E0277]: the trait bound `T: Trait` is not satisfied
  --> $DIR/generic_underconstrained.rs:6:1
   |
LL | type Underconstrained<T: Trait> = impl 'static;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `T`
...
LL | fn underconstrain<T>(_: T) -> Underconstrained<T> {
   |                   - help: consider restricting this bound: `T: Trait`
   |
   = note: the return type of a function must have a statically known size

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.