Here, we were seeing that A<X>:: is a template specialization, so we tried to treat it as entering the scope of A<X>. But since A is an alias template, that doesn't make sense. Fixed by not considering alias templates for this treatment.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 7fde9bb020c7be786c791e485261e28e7b0d3ccf Author: Jason Merrill <ja...@redhat.com> Date: Thu Mar 23 16:21:34 2017 -0400 PR c++/77339 - ICE with invalid use of alias template. * pt.c (lookup_template_class_1): Don't try to enter the scope of an alias template. diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 5259dad..cbe8082 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -8682,9 +8682,9 @@ lookup_template_class_1 (tree d1, tree arglist, tree in_decl, tree context, || !PRIMARY_TEMPLATE_P (gen_tmpl) || currently_open_class (template_type)) { - tree tinfo = TYPE_TEMPLATE_INFO_MAYBE_ALIAS (template_type); + tree tinfo = TYPE_TEMPLATE_INFO (template_type); - if (comp_template_args (TI_ARGS (tinfo), arglist)) + if (tinfo && comp_template_args (TI_ARGS (tinfo), arglist)) return template_type; } diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-58.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-58.C new file mode 100644 index 0000000..0ae1c49 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-58.C @@ -0,0 +1,7 @@ +// PR c++/77339 +// { dg-do compile { target c++11 } } + +template < typename > using A = int; + +//OK: template < typename X > A < X > a; +template < typename X > A < X >::a; // { dg-error "" }