https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81134
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- To determine the type of the conditional expression it's necessary to know the types of both GCD<N%M, M>::value and GCD<N, M%N>::value, which requires instantiating both of GCD<N%M, M> and GCD<N, M%N>, which triggers the infinite recursion.
