[Bug c++/80096] New: [c++1z] ICE with auto template parameter

["reichelt at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80096

            Bug ID: 80096
           Summary: [c++1z] ICE with auto template parameter
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: reichelt at gcc dot gnu.org
  Target Milestone: ---

The following valid code snippet triggers an ICE on trunk
(when compiled with -std=c++1z):

=================================
template<auto> struct A
{
  template<int> struct B {};
};

A<0> a;
=================================

bug.cc: In instantiation of 'struct A<0>':
bug.cc:6:6:   required from here
bug.cc:3:24: internal compiler error: in tsubst, at cp/pt.c:13524
   template<int> struct B {};
                        ^
0x67936b tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:13524
0x676ef6 tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:13394
0x663db0 tsubst_copy
        ../../gcc/gcc/cp/pt.c:14963
0x68a9cf tsubst_copy
        ../../gcc/gcc/cp/pt.c:14426
0x68a9cf tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:17920
0x66a140 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../gcc/gcc/cp/pt.c:16458
0x67c626 tsubst_template_args
        ../../gcc/gcc/cp/pt.c:11697
0x699474 tsubst_aggr_type
        ../../gcc/gcc/cp/pt.c:11899
0x676aaa tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:13404
0x6962e2 lookup_template_class_1
        ../../gcc/gcc/cp/pt.c:8738
0x6962e2 lookup_template_class(tree_node*, tree_node*, tree_node*, tree_node*,
int, int)
        ../../gcc/gcc/cp/pt.c:9009
0x699499 tsubst_aggr_type
        ../../gcc/gcc/cp/pt.c:11905
0x676aaa tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:13404
0x673ac8 tsubst_decl
        ../../gcc/gcc/cp/pt.c:12114
0x676ce7 tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:13322
0x6ac108 instantiate_class_template_1
        ../../gcc/gcc/cp/pt.c:10514
0x6ac108 instantiate_class_template(tree_node*)
        ../../gcc/gcc/cp/pt.c:10798
0x750ca6 complete_type(tree_node*)
        ../../gcc/gcc/cp/typeck.c:133
0x610199 start_decl_1(tree_node*, bool)
        ../../gcc/gcc/cp/decl.c:5208
0x637bbf start_decl(cp_declarator const*, cp_decl_specifier_seq*, int,
tree_node*, tree_node*, tree_node**)
        ../../gcc/gcc/cp/decl.c:5171
Please submit a full bug report, [etc.]

Btw, clang 4.0.0 accepts the code.