Call Hierarchy Calls To doesn't work on a function call whose definition isn't available

[sean-mcmanus]

Use code

extern void foo();
int main()
{
  foo(); // this also repros with printf(""), and also adding #include <stdio.h> at the top
  return 0;
}

Do Call Hierarchy on main and the make sure it's in Calls To mode and then do Call Hierarchy on foo.

Bug: It doesn't give results. It works with VS, i.e it should show main as a caller of foo. This repros for any function calls that are available via static or dynamically linked libraries (no definition available).

Bug2: For the Calls From case, VS says "The function definition could not be located" but we don't show a message -- is it possible to add a message?