error: tail calling closures directly is not allowed
  --> $DIR/closure.rs:6:5
   |
LL |     become (|| ())();
   |     ^^^^^^^^^^^^^^^^
   |
help: try casting the closure to a function pointer type
   |
LL |     become ((|| ()) as fn() -> _)();
   |            +        +++++++++++++

error: tail calling closures directly is not allowed
  --> $DIR/closure.rs:11:5
   |
LL |     become (|()| ())(());
   |     ^^^^^^^^^^^^^^^^^^^^
   |
help: try casting the closure to a function pointer type
   |
LL |     become ((|()| ()) as fn(_) -> _)(());
   |            +          ++++++++++++++

error: tail calling closures directly is not allowed
  --> $DIR/closure.rs:16:5
   |
LL |     become (|(), _| ())((), 1);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
help: try casting the closure to a function pointer type
   |
LL |     become ((|(), _| ()) as fn(_, _) -> _)((), 1);
   |            +             +++++++++++++++++

error: tail calling closures directly is not allowed
  --> $DIR/closure.rs:22:5
   |
LL |     become f((), ((), ()));
   |     ^^^^^^^^^^^^^^^^^^^^^^
   |
help: try casting the closure to a function pointer type
   |
LL |     become (f as fn(_, _) -> _)((), ((), ()));
   |            +  +++++++++++++++++

error: aborting due to 4 previous errors