error[E0658]: the precise format of `Fn`-family traits' type parameters is subject to change. Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead (see issue #29625)
  --> $DIR/issue-23024.rs:19:35
   |
LL |     println!("{:?}",(vfnfer[0] as Fn)(3));
   |                                   ^^
   |
   = help: add #![feature(unboxed_closures)] to the crate attributes to enable

error[E0243]: wrong number of type arguments: expected 1, found 0
  --> $DIR/issue-23024.rs:19:35
   |
LL |     println!("{:?}",(vfnfer[0] as Fn)(3));
   |                                   ^^ expected 1 type argument

error[E0191]: the value of the associated type `Output` (from the trait `std::ops::FnOnce`) must be specified
  --> $DIR/issue-23024.rs:19:35
   |
LL |     println!("{:?}",(vfnfer[0] as Fn)(3));
   |                                   ^^ missing associated type `Output` value

error: aborting due to 3 previous errors

Some errors occurred: E0191, E0243, E0658.
For more information about an error, try `rustc --explain E0191`.