Unique function types are not unique enough #23733
Description
In this example
trait Check: std::marker::MarkerTrait {
fn check();
}
impl Check for u8 {
fn check() { println!("u8"); }
}
impl Check for u16 {
fn check() { println!("u16"); }
}
fn f<T: Check>() {
T::check();
}
fn main() {
fn same_type<T>(_: T, _: T) {}
same_type(f::<u8>, f::<u16>);
println!("{} {}", f::<u8> as usize, f::<u16> as usize);
}
functions f::<u8> and f::<u16> have the same type fn() {f} tied to the id of the generic function item, but different function pointers. So, in general case a function pointer can't be unambiguosly obtained from function item's type.