pragma mangle on extern(C) in function body

[Sebastiaan Koppe via Digitalmars-d-learn]

While it is perfectly ok to define an extern(C) function in a 
function method, I can't seem to get pragma(mangle, "...") on it 
to work.

---
pragma(mangle, "Foo")    // Ok
extern(C) void foo();
void main() {
    pragma(mangle, "Bar")    // Error....
    extern(C) void bar();
}
---

Any idea why?