In: struct bottom {}; template<typename v, typename next> struct node: public next { v val; }; enum a {b, c}; enum x{y, z}; struct foo : public node<a, node<x, bottom> > {}; template<typename T, typename U> void bar(node<T, U>&) {} int main() { foo f; bar(f); return 0; } you get: ~/ootbc/members/src$ g++ foo.cc foo.cc: In function `int main()': foo.cc:10: error: no matching function for call to `bar(foo&)' Actually, there is a matching function, but the call is ambiguous because there are two matching base classes. The diagnostic should say so and identify the matching bases. This is reported correctly by other ambiguous calls where two different functions are matches to the argument set. In this case one function has two different matches, but the user's need in the diagnostic is the same: show what the compiler found. Ivan
The same case but using derivation from classes rather than templates: struct foo {}; struct bar : public foo {}; struct baz : public bar {}; struct baf : public foo, public baz {}; void F(foo&) {} int main() { baf b; F(b); return 0; } gives a much better diagnostic: ~/ootbc/members/src$ g++ foo.cc foo.cc:4: warning: direct base `foo' inaccessible in `baf' due to ambiguity foo.cc: In function `int main()': foo.cc:6: error: `foo' is an ambiguous base of `baf'
I'm absolutely positive this is a duplicate of a fair number of other PRs, though I can't find one with a 20 second search. PR 13979 may be one, but doesn't have a really short testcase so I can't tell for sure. W.
*** This bug has been marked as a duplicate of 16057 ***