~/test/O$ cat break.cpp #include <iostream> template <typename A, typename B> struct MutualRecursion { static const int a = MutualR

~/test/O$ cat break.cpp #include <iostream> template <typename A, typename B> struct MutualRecursion { static const int a = MutualRecursion< B, A >::b ; static const int b = MutualRecursion< B, A >::a ; }; int main( int argc, char ** argv ){ std::cout << MutualRecursion< float, int >::b << std::endl; return 0; }; ~/test/O$ clang break.cpp break.cpp:6:49: error: no member named 'b' in 'MutualRecursion<float, int>' static const int a = MutualRecursion< B, A >::b ; ~~~~~~~~~~~~~~~~~~~~~~~~~^ break.cpp:6:24: note: in instantiation of template class 'MutualRecursion<int, float>' requested here static const int a = MutualRecursion< B, A >::b ; ^ break.cpp:11:16: note: in instantiation of template class 'MutualRecursion<float, int>' requested here std::cout << MutualRecursion< float, int >::b << std::endl; ^ break.cpp:7:24: error: in-class initializer is not a constant expression static const int b = MutualRecursion< B, A >::a ; ^~~~~~~~~~~~~~~~~~~~~~~~~~ 2 errors generated. ~/test/O$ ~~This is definitely a bug in clang~~. clang doesn't find the member "b" here because it's referencing the cached still-in-construction version of the template. Furthermore, it still does this even when "b" is a regular constant. // static const int b = MutualRecursion< B, A >::a ; static const int b = 10 ; gcc, since it appears to always instantiate a new copy of the template compiles successfully for when "b = 10". ~~clang needs to wait until it has fully constructed a type before putting it into the cache, even if it might be slower in some recursive cases. Better than wrong in them.~~ I don't know if clang is in the wrong here, so I'm rejecting a couple of statements. Its method does not allow for compilation in these circumstances, but may be technically permissible, even if gcc jives with how I envision templates operating.