error[E0277]: the trait bound `T: Trait` is not satisfied
  --> $DIR/generic_underconstrained.rs:9:31
   |
LL | fn underconstrain<T>(_: T) -> Underconstrained<T> {
   |                               ^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `T`
   |
note: required by a bound on the type alias `Underconstrained`
  --> $DIR/generic_underconstrained.rs:6:26
   |
LL | type Underconstrained<T: Trait> = impl Send;
   |                          ^^^^^ required by this bound
help: consider restricting type parameter `T`
   |
LL | fn underconstrain<T: Trait>(_: T) -> Underconstrained<T> {
   |                    +++++++

error: aborting due to previous error

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