Duplicate function has no line number

[Thierry Delisle]

trait is_a_thing(otype T) {
	T & ?=?( T &, T );
};

forall(otype T | is_a_thing(T))
T foo();

results in an error with no line number:

error: duplicate function definition for ?=?: pointer to function
... with parameters
  reference to instance of type T (not function type) 
  instance of type T (not function type) 
... returning 
  _retval__operator_assign: reference to instance of type T (not function type) 
  ... with attributes: 
    Attribute with name: unused

[Rob Schluntz <rschlunt@…>]

In d53772d:

Transfer location from function to object in FixFunction? [fixes #98]