[Bug c++/94034] [10 Regression] Broken diagnostic: 'result_decl' not supported by dump_expr

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94034

--- Comment #5 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Here is a rejects-valid testcase caused by the same underlying issue:

$ cat testcase.C
struct A { A *p = this; int n; };

constexpr A
foo()
{
  return {};
}

constexpr A
bar()
{
  A a = foo();
  a.p->n = 5;
  return a;
}

static_assert(bar().n == 5);

$ g++ -std=c++2a testcase.C
testcase.C:17:23: error: non-constant condition for static assertion
   17 | static_assert(bar().n == 5);
      |               ~~~~~~~~^~~~
testcase.C:17:19:   in ‘constexpr’ expansion of ‘bar()’
testcase.C:17:23: error: modification of ‘‘result_decl’ not supported by
dump_expr<expression error>’ is not a constant expression