Can you help me figure out how to define an fn type that can take values of method type?

struct Foo<'a>(&'a u32);

impl<'a> Foo<'a> {
    fn bar(&mut self) {
        type Func = fn(&mut Foo); // Same error with this
        //type Func = for<'b> fn(&'b mut Foo<'_>); // Same error with this
        let f: Func = Foo::baz;
        f(self)
    }
    
    fn baz(&mut self) {}
}

error[E0308]: mismatched types
 --> src/main.rs:7:23
  |
7 |         let f: Func = Foo::baz;
  |                ----   ^^^^^^^^ one type is more general than the other
  |                |
  |                expected due to this
  |
  = note: expected fn pointer `for<'a, 'b> fn(&'a mut Foo<'b>)`
                found fn item `for<'a> fn(&'a mut Foo<'_>) {Foo::<'_>::baz}`

For more information about this error, try `rustc --explain E0308`.
error: could not compile `playground` (bin "playground") due to 1 previous error

Playground

The complicating factor here happens to be that the self type has a lifetime parameter, and the Funcs above are interpreted as for<'a, 'b> fn(&'a mut Foo<'b>).

In addition to the solution, I'd appreciate an understanding of the problem and the precise distinction the compiler is making.

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