error[E0277]: the trait bound `(): const Tr` is not satisfied
  --> $DIR/const-closure-trait-method-fail.rs:18:23
   |
LL | const _: () = assert!(need_const_closure(Tr::a) == 42);
   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error

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