Const-eval failure in `const fn` does not print the path of what we evaluate

[RalfJung]

Consider this code:

struct S<T>(T);

const fn oopsie() -> ! {
    panic!();
}

impl<T> S<T> {
    const C1: i32 = panic!();
    const C2: i32 = oopsie();
}

fn main() {
    S::<i32>::C1; // or C2
}

If we use C1, we get the following:

error[E0080]: evaluation of `S::<i32>::C1` failed
 --> src/main.rs:8:21
  |
8 |     const C1: i32 = panic!();
  |                     ^^^^^^^^ evaluation panicked: explicit panic

But if we use C2, we get:

error[E0080]: evaluation of `oopsie` failed
 --> src/main.rs:9:21
  |
9 |     const C2: i32 = oopsie();
  |                     ^^^^^^^^ evaluation panicked: explicit panic
  |
note: inside `oopsie`
 --> src/main.rs:4:5
  |
4 |     panic!();
  |     ^^^^^^^^ the failure occurred here

Note that it says "evaluation of oopsie failed"; I would have expected "evaluation of S::<i32>::C2 failed". That's where the span points at, too.

Cc @oli-obk