If we're adding the enclosing template args, we also need to switch to looking at the most general template.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 35fe583ade362f018f095435980424f1244ab92f Author: Jason Merrill <ja...@redhat.com> Date: Thu Dec 22 13:27:26 2016 -0500 PR c++/78906 - ICE with member variable template * pt.c (finish_template_variable): Use most_general_template. diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 7711546..3fa2ce9 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -9000,6 +9000,7 @@ finish_template_variable (tree var, tsubst_flags_t complain) tree tmpl_args = DECL_TI_ARGS (DECL_TEMPLATE_RESULT (templ)); arglist = add_outermost_template_args (tmpl_args, arglist); + templ = most_general_template (templ); tree parms = DECL_TEMPLATE_PARMS (templ); arglist = coerce_innermost_template_parms (parms, arglist, templ, complain, /*req_all*/true, diff --git a/gcc/testsuite/g++.dg/cpp1y/var-templ54.C b/gcc/testsuite/g++.dg/cpp1y/var-templ54.C new file mode 100644 index 0000000..f52f764 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/var-templ54.C @@ -0,0 +1,13 @@ +// PR c++/78906 +// { dg-do compile { target c++14 } } + +template <typename> struct A { static constexpr int digits = 0; }; +template <typename> struct B { + template <int, typename MaskInt = int, int = A<MaskInt>::digits> + static constexpr int XBitMask = 0; +}; +struct C { + using ReferenceHost = B<int>; + template <int> static decltype(ReferenceHost::XBitMask<0>) XBitMask; +}; +int main() { C::XBitMask<0>; }