[Bug c++/95999] New: ICE in tree check: expected integer_cst, have var_decl in get_len, at tree.h:5951

[webrown.cpp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95999

            Bug ID: 95999
           Summary: ICE in tree check: expected integer_cst, have var_decl
                    in get_len, at tree.h:5951
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: error-recovery, ice-on-invalid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: haoxintu at gmail dot com
                CC: webrown.cpp at gmail dot com
  Target Milestone: ---
                CC: webrown.cpp at gmail dot com

This code, bug.cc, reduced by C-Reduce, makes GCC-trunk ICE.

$cat bug.cc
int a;
enum struct b;
template <typename = enum struct b { c = a d } 
template <> enum struct b { e };


$g++ bug.cc
bug.cc:3:42: error: the value of ‘a’ is not usable in a constant expression
    3 | template <typename = enum struct b { c = a d }
      |                                          ^
bug.cc:1:5: note: ‘int a’ is not const
    1 | int a;
      |     ^
bug.cc:3:44: error: expected ‘}’ before ‘d’
    3 | template <typename = enum struct b { c = a d }
      |                                    ~       ^
bug.cc:3:44: error: expected ‘>’ before ‘d’
bug.cc:3:46: error: expected unqualified-id before ‘}’ token
    3 | template <typename = enum struct b { c = a d }
      |                                              ^
bug.cc:3:46: error: expected declaration before ‘}’ token
bug.cc:4:29: internal compiler error: tree check: expected integer_cst, have
var_decl in get_len, at tree.h:5951
    4 | template <> enum struct b { e };
      |                             ^
0x7c2dcf tree_check_failed(tree_node const*, char const*, int, char const*,
...)
        ../../gcc/tree.c:9685
0x61582f tree_check(tree_node const*, char const*, int, char const*, tree_code)
        ../../gcc/tree.h:3557
0x61582f wi::extended_tree<192>::get_len() const
        ../../gcc/tree.h:5951
0x61582f wi::int_traits<generic_wide_int<wi::extended_tree<192> >
>::decompose(long*, unsigned int, generic_wide_int<wi::extended_tree<192> >
const&)
        ../../gcc/wide-int.h:985
0x61582f wide_int_ref_storage<true,
false>::wide_int_ref_storage<generic_wide_int<wi::extended_tree<192> >
>(generic_wide_int<wi::extended_tree<192> > const&, unsigned int)
        ../../gcc/wide-int.h:1034
0x61582f generic_wide_int<wide_int_ref_storage<true, false>
>::generic_wide_int<generic_wide_int<wi::extended_tree<192> >
>(generic_wide_int<wi::extended_tree<192> > const&, unsigned int)
        ../../gcc/wide-int.h:790
0x61582f wi::binary_traits<generic_wide_int<wi::extended_tree<192> >, int,
wi::int_traits<generic_wide_int<wi::extended_tree<192> > >::precision_type,
wi::int_traits<int>::precision_type>::result_type
wi::add<generic_wide_int<wi::extended_tree<192> >,
int>(generic_wide_int<wi::extended_tree<192> > const&, int const&, signop,
wi::overflow_type*)
        ../../gcc/wide-int.h:2467
0x61582f build_enumerator(tree_node*, tree_node*, tree_node*, tree_node*,
unsigned int)
        ../../gcc/cp/decl.c:15857
0x9a2447 cp_parser_enumerator_definition
        ../../gcc/cp/parser.c:19545
0x9a2447 cp_parser_enumerator_list
        ../../gcc/cp/parser.c:19474
0x9a2447 cp_parser_enum_specifier
        ../../gcc/cp/parser.c:19405
0x9a2447 cp_parser_type_specifier
        ../../gcc/cp/parser.c:17734
0x9a2a02 cp_parser_decl_specifier_seq
        ../../gcc/cp/parser.c:14410
0x9c8f35 cp_parser_single_declaration
        ../../gcc/cp/parser.c:29459
0x9ca0f0 cp_parser_explicit_specialization
        ../../gcc/cp/parser.c:17654
0x9ccac9 cp_parser_declaration
        ../../gcc/cp/parser.c:13430
0x9cd06a cp_parser_translation_unit
        ../../gcc/cp/parser.c:4761
0x9cd06a c_parse_file()
        ../../gcc/cp/parser.c:44043
0xae4dbb c_common_parse_file()
        ../../gcc/c-family/c-opts.c:1190
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

$g++ --version
g++ (GCC) 11.0.0 20200626 (experimental)
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This is free software; see the source for copying conditions.  There is NO
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