[Bug c++/122374] ICE on assignment expression in requires clause of copy constructor

[eczbek.void at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122374

--- Comment #1 from eczbek.void at gmail dot com ---
This might be related? Invalid example but causes a segfault:
https://godbolt.org/z/z3v1fazdT

```
template<int x>
struct S {
        S() {}

        void operator=(int) {}

        S(const S&) requires(!requires { this->operator=(0); }) {}
};

int main() {
        S<0> a;
        auto b = a;
}
```

```
<source>: In function 'int main()':
<source>:12:18: error: no matching function for call to 'S<0>::S(S<0>&)'
   12 |         auto b = a;
      |                  ^
  • there are 2 candidates
    • candidate 1: 'S<x>::S(const S<x>&) requires
!requires{((S<x>*)this)->.S<x>::operator=(int)(0);} [with int x = 0]'
      <source>:7:9:
          7 |         S(const S&) requires(!requires { this->operator=(0); })
{}
            |         ^
      • constraints not satisfied
        • <source>: In instantiation of 'S<x>::S(const S<x>&) requires
!requires{((S<x>*)this)->.S<x>::operator=(int)(0);} [with int x = 0]':
        • required from here
          <source>:12:11:   
             12 |         auto b = a;
                |                  ^
        • required by the constraints of 'template<int x> S<x>::S(const S<x>&)
requires !requires{((S<x>*)this)->.S<x>::operator=(int)(0);}'
          <source>:7:2:   
              7 |         S(const S&) requires(!requires { this->operator=(0);
}) {}
                |         ^
        • internal compiler error: Segmentation fault
          <source>:7:56:
              7 |         S(const S&) requires(!requires { this->operator=(0);
}) {}
                |                                          ~~~~~~~~~~~~~~^
0x28de808 diagnostics::context::diagnostic_impl(rich_location*,
diagnostics::metadata const*, diagnostics::option_id, char const*,
__va_list_tag (*) [1], diagnostics::kind)
        ???:0
0x28d35fb internal_error(char const*, ...)
        ???:0
0xb97786 tsubst_requires_expr(tree_node*, tree_node*, int, tree_node*)
        ???:0
0xb98d38 diagnose_constraints(unsigned long, tree_node*, tree_node*)
        ???:0
0xb288bf build_new_method_call(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>**, tree_node*, int, tree_node**, int)
        ???:0
0xb2999d build_special_member_call(tree_node*, tree_node*, vec<tree_node*,
va_gc, vl_embed>**, tree_node*, int, int)
        ???:0
0xbbf408 ocp_convert(tree_node*, tree_node*, int, int, int)
        ???:0
0xc41fda build_aggr_init(tree_node*, tree_node*, int, int)
        ???:0
0xc0c83e cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int,
cp_decomp*)
        ???:0
0xd3fa13 c_parse_file()
        ???:0
0xeb0479 c_common_parse_file()
        ???:0
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1
```