[Bug c++/84804] New: [8 Regression] ICE with lambda in default argument

[reichelt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84804

            Bug ID: 84804
           Summary: [8 Regression] ICE with lambda in default argument
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: ice-on-invalid-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 inavlid code snippet triggers an ICE on trunk:

=================================================
template<int> struct A
{
  friend void foo(int i = []{ return 0;}()) {}
};

void bar()
{
  A<0>::foo();
}
=================================================

bug.cc: In instantiation of 'struct A<0>':
bug.cc:8:7:   required from here
bug.cc:3:41: internal compiler error: tree check: expected class 'type', have
'exceptional' (error_mark) in tsubst_lambda_expr, at cp/pt.c:17155
   friend void foo(int i = []{ return 0;}()) {}
                           ~~~~~~~~~~~~~~^~
0x78b66e tree_class_check_failed(tree_node const*, tree_code_class, char
const*, int, char const*)
        ../../gcc/gcc/tree.c:9385
0x639e0e tree_class_check(tree_node*, tree_code_class, char const*, int, char
const*)
        ../../gcc/gcc/tree.h:3255
0x639e0e tsubst_lambda_expr(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:17155
0x95f422 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:18495
0x96036f tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:17820
0x96dd9f tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:17255
0x96dd9f tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../gcc/gcc/cp/pt.c:16987
0x95c936 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../gcc/gcc/cp/pt.c:16175
0x95c936 tsubst_default_argument(tree_node*, int, tree_node*, tree_node*, int)
        ../../gcc/gcc/cp/pt.c:12346
0x95e2e6 tsubst_default_arguments
        ../../gcc/gcc/cp/pt.c:12404
0x95e2e6 tsubst_function_decl
        ../../gcc/gcc/cp/pt.c:12651
0x979c56 tsubst_decl
        ../../gcc/gcc/cp/pt.c:12924
0x9740ef tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:13812
0x98c962 tsubst_friend_function
        ../../gcc/gcc/cp/pt.c:9948
0x98c962 instantiate_class_template_1
        ../../gcc/gcc/cp/pt.c:10989
0x98c962 instantiate_class_template(tree_node*)
        ../../gcc/gcc/cp/pt.c:11055
0x9d38fd complete_type(tree_node*)
        ../../gcc/gcc/cp/typeck.c:136
0x9321aa cp_parser_nested_name_specifier_opt
        ../../gcc/gcc/cp/parser.c:6445
0x933cb5 cp_parser_simple_type_specifier
        ../../gcc/gcc/cp/parser.c:17177
0x92de15 cp_parser_type_specifier
        ../../gcc/gcc/cp/parser.c:16850
Please submit a full bug report, [etc.]

The regression was introduced between 2017-11-09 and 2017-11-17.