Functions should have a unique, unnameable type, not `fn(...) -> ...`

[narpfel]

I tried this code:

fn f() {}
fn g() {}

fn main() {
    let mut x = f;
    x = g;
}

I expected to see this happen: This should type error, as f and g have different types:

error[E0308]: mismatched types
 --> <source>:6:9
  |
6 |     x = g;
  |         ^ expected fn item, found a different fn item
  |
  = note: expected fn item `fn() {f}`
             found fn item `fn() {g}`
  = note: different `fn` items always have unique types, even if their signatures are the same
  = help: change the expected type to be function pointer `fn()`
  = help: if the expected type is due to type inference, cast the expected `fn` to a function pointer: `f as fn()`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.
Compiler returned: 1

Instead, this happened: Compiles without error.

Godbolt link: https://godbolt.org/z/4bz9Pdjxr

Meta

• What version of Rust GCC were you using, git sha if possible. be27571

gccrs (Compiler-Explorer-Build-gcc-be27571c110d99fe55324a9c2b6622787b08fb52-binutils-2.38) 13.0.1 20230221 (experimental)