error[E0107]: function takes 2 generic arguments but 1 generic argument was supplied
  --> $DIR/not-enough-args.rs:4:5
   |
LL |     f::<[u8]>("a", b"a");
   |     ^   ---- supplied 1 generic argument
   |     |
   |     expected 2 generic arguments
   |
note: function defined here, with 2 generic parameters: `T`, `U`
  --> $DIR/not-enough-args.rs:1:4
   |
LL | fn f<T: ?Sized, U: ?Sized>(_: impl AsRef<T>, _: impl AsRef<U>) {}
   |    ^ -          -
help: add missing generic argument
   |
LL |     f::<[u8], U>("a", b"a");
   |             +++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0107`.