[Bug c++/20812] contextual overload resolution failure for a member name found in two base classes

["SWElef at post dot sk" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From SWElef at post dot sk  2005-04-15 07:30 -------
I was wrong. std:10.2/2 (member name lookup) says

  [snip] If the resulting set of declarations are not all from sub-objects of
  the same type, or the set has a nonstatic member and includes members from
  distinct sub-objects, there is an ambiguity and the program is ill-formed.
  [snip]

So the deduction may not succeed. On the other hand, IIRC it is also not
supposed to fail since the paragraph 14.8.2/2 that names all reasons for
deduction failure does not contain anything about this specific case. The
only reason that seems a little similar reads

  Attempting to use a type in the qualifier portion of a qualified name that
  names a type when that type does not contain the specified member, or if the
  specified member is not a type where a type is required.

and in this case the named type _contains_ the specified member, it's just
ambiguous.

To expose the problem I wrote this new snippet:

struct B1{ typedef int T; };
struct B2{ typedef int T; };
struct D : B1, B2 { };

template <typename X>
typename X::T foo() { return X::T(); }

int main(){ foo<D>(); }

gcc reports "error: no matching function for call to `foo()'". Comeau Online
says "error: "D::T" is ambiguous" which is very different (and IIRC correct).

May be this PR should be resolved as INVALID and another one should be written
with this snippet and a more appropriate subject.

Regards,
Vladimir Marko


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20812