error[E0308]: mismatched types
  --> $DIR/signature-mismatch.rs:4:54
   |
LL |     let _ = [std::ops::Add::add, std::ops::Mul::mul, std::ops::Mul::mul as fn(_, &_)];
   |                                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
   |
   = note: expected fn pointer `fn(_, _) -> _`
              found fn pointer `for<'a> fn(_, &'a _) -> ()`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.