error[E0107]: function takes 1 generic argument but 2 generic arguments were supplied
  --> $DIR/explicit-generic-args-for-impl.rs:4:5
   |
LL |     foo::<str, String>("".to_string());
   |     ^^^        ------ help: remove this generic argument
   |     |
   |     expected 1 generic argument
   |
note: function defined here, with 1 generic parameter: `T`
  --> $DIR/explicit-generic-args-for-impl.rs:1:4
   |
LL | fn foo<T: ?Sized>(_f: impl AsRef<T>) {}
   |    ^^^ -
   = note: `impl Trait` cannot be explicitly specified as a generic argument

error: aborting due to 1 previous error

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