[Bug c++/66426] ICE: unexpected expression ‘int?=(Constructible())...=?UTF-8?Q?’ of kind expr_pack_expansion

[jamrial at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66426

--- Comment #1 from James Almer <jamrial at gmail dot com> ---
FWIW, testcase from Comment 2 of pr66405 unedited:

[jamrial@archVM ~]$ cat pr66405_c2.cpp
template <typename> struct A;
template <bool> struct enable_if;
template <typename T, T> struct B;
template <bool... Bools> using and_c = A<B<bool, Bools || true...>>;
template <typename...> using Constructible = int;
template <typename... Ts> struct common_tuple {
  template <
      typename... Us,
      typename enable_if<and_c<(int)Constructible<Ts, Us>()...>::value>::type>
  common_tuple();
  void foo();
};
template <> void common_tuple<>::foo(){};

[jamrial@archVM ~]$ g++-4.9 -O2 -std=c++11 -c pr66405_c2.cpp
pr66405_c2.cpp:9:63: internal compiler error: unexpected expression
‘int(Constructible())...’ of kind expr_pack_expansion
       typename enable_if<and_c<(int)Constructible<Ts, Us>()...>::value>::type>
                                                               ^
0x61cbd6 cxx_eval_constant_expression
        /home/jamrial/gcc-4.9-20150603/gcc/cp/semantics.c:9833
0x61e5b6 cxx_eval_outermost_constant_expr
        /home/jamrial/gcc-4.9-20150603/gcc/cp/semantics.c:9853
0x585cb0 convert_nontype_argument
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:5698
0x585cb0 convert_template_argument
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:6590
0x582252 coerce_template_parameter_pack
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:6713
0x582252 coerce_template_parms
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:6922
0x586c70 lookup_template_class_1
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:7594
0x586c70 lookup_template_class(tree_node*, tree_node*, tree_node*, tree_node*,
int, int)
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:7895
0x6149b2 finish_template_type(tree_node*, tree_node*, int)
        /home/jamrial/gcc-4.9-20150603/gcc/cp/semantics.c:2969
0x5d63fa cp_parser_template_id
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:13464
0x5d6613 cp_parser_class_name
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:19195
0x5cc673 cp_parser_qualifying_entity
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:5538
0x5cc673 cp_parser_nested_name_specifier_opt
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:5263
0x5e0ee2 cp_parser_simple_type_specifier
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:14666
0x5c3ebd cp_parser_type_specifier
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:14412
0x5c65cb cp_parser_type_specifier_seq
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:18137
0x5d4ee2 cp_parser_type_id_1
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:18010
0x5d4fde cp_parser_template_type_arg
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:18059
0x5d51d8 cp_parser_template_argument
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:13840
0x5d51d8 cp_parser_template_argument_list
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:13750



And testcase taken from gcc/testsuite/g++.dg/cpp0x/variadic-alias1.C (added in
svn 224163)

[jamrial@archVM ~]$ cat Varidic-alias1.C
template <typename T, T...> struct B;
template <bool... Bools> using and_c = B<bool, +Bools...>;
template <typename T, typename U> using Constructible = int;
template <typename... Ts> struct common_tuple {
  template <typename... Us,
           typename = and_c<Constructible<Ts, Us>{}...> >
    common_tuple();
  void foo();
};
template <> void common_tuple<>::foo(){}

[jamrial@archVM ~]$ g++-4.9 -O2 -std=c++11 -c Varidic-alias1.C
Varidic-alias1.C:6:55: internal compiler error: unexpected expression ‘{}...’
of kind expr_pack_expansion
            typename = and_c<Constructible<Ts, Us>{}...> >
                                                       ^
0x61cbd6 cxx_eval_constant_expression
        /home/jamrial/gcc-4.9-20150603/gcc/cp/semantics.c:9833
0x61e5b6 cxx_eval_outermost_constant_expr
        /home/jamrial/gcc-4.9-20150603/gcc/cp/semantics.c:9853
0x585cb0 convert_nontype_argument
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:5698
0x585cb0 convert_template_argument
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:6590
0x582252 coerce_template_parameter_pack
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:6713
0x582252 coerce_template_parms
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:6922
0x586c70 lookup_template_class_1
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:7594
0x586c70 lookup_template_class(tree_node*, tree_node*, tree_node*, tree_node*,
int, int)
        /home/jamrial/gcc-4.9-20150603/gcc/cp/pt.c:7895
0x6149b2 finish_template_type(tree_node*, tree_node*, int)
        /home/jamrial/gcc-4.9-20150603/gcc/cp/semantics.c:2969
0x5d63fa cp_parser_template_id
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:13464
0x5d6613 cp_parser_class_name
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:19195
0x5cc673 cp_parser_qualifying_entity
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:5538
0x5cc673 cp_parser_nested_name_specifier_opt
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:5263
0x5e0ee2 cp_parser_simple_type_specifier
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:14666
0x5c3ebd cp_parser_type_specifier
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:14412
0x5c65cb cp_parser_type_specifier_seq
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:18137
0x5d4ee2 cp_parser_type_id_1
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:18010
0x5db5c2 cp_parser_type_id
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:18050
0x5db5c2 cp_parser_type_parameter
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:13161
0x5daeac cp_parser_template_parameter
        /home/jamrial/gcc-4.9-20150603/gcc/cp/parser.c:12994