[Bug c++/118319] New: ICE Segmentation fault in friend declaration with default argument assigned to an empty lambda expression

[wangbopku15 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118319

            Bug ID: 118319
           Summary: ICE Segmentation fault in friend declaration with
                    default argument assigned to an empty lambda
                    expression
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wangbopku15 at gmail dot com
  Target Milestone: ---

Test input:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

template <int> struct S{
      friend void foo (int a = []{}());
};

void foo(int a){};

int main(){
        S<0> t;    
        foo();
}

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Compiler Output:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

<source>:2:19: error: friend declaration of 'void foo(int)' specifies default
arguments and isn't a definition [-Wtemplate-body]
    2 |       friend void foo (int a = []{}());
      |                   ^~~
<source>: In instantiation of 'struct S<0>':
<source>:8:14:   required from here
    8 |         S<0> t;
      |              ^
<source>:2:19: error: friend declaration of 'void foo(int)' specifies default
arguments and isn't the only declaration [-fpermissive]
    2 |       friend void foo (int a = []{}());
      |                   ^~~
<source>:5:6: note: previous declaration of 'void foo(int)'
    5 | void foo(int a){};
      |      ^~~
<source>: In function 'int main()':
<source>:9:12: internal compiler error: Segmentation fault
    9 |         foo();
      |         ~~~^~
0x2938005 diagnostic_context::diagnostic_impl(rich_location*,
diagnostic_metadata const*, diagnostic_option_id, char const*, __va_list_tag
(*) [1], diagnostic_t)
        ???:0
0x294ee06 internal_error(char const*, ...)
        ???:0
0xae4424 set_flags_from_callee(tree_node*)
        ???:0
0x17e3b1c walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, false, default_hash_traits<tree_node*> >*,
tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, false, default_hash_traits<tree_node*> >*))
        ???:0
0xd8da22 break_out_target_exprs(tree_node*, bool)
        ???:0
0xaeac9c convert_default_arg(tree_node*, tree_node*, tree_node*, int, int)
        ???:0
0xb0100e build_new_function_call(tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ???:0
0xd65696 finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
bool, int)
        ???:0
0xce562a c_parse_file()
        ???:0
0xe44f99 c_common_parse_file()
        ???:0
Please submit a full bug report, with preprocessed source.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Note that the template instantiation of 'S<0> t' here before the calling of
'foo' is necessary here.

See https://godbolt.org/z/jcrKesYTh