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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/104620] FAIL: g++.dg/cpp23/consteval-if2.C  -std=gnu++20 
 (test for errors)
Date: Thu, 24 Mar 2022 13:29:29 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104620

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Another testcase to consider is:
consteval int foo (int x) { return x; }
consteval int bar () { return 2; }
constexpr int baz (int x) { return x; }

template <typename T>
constexpr int
qux (int x)
{
  int r =3D 0;
  if consteval          // { dg-warning "'if consteval' only available with=
" ""
{ target c++20_only } }
    {
      r +=3D 2 * bar ();
    }
  else
    {
      r +=3D foo (8 * baz (0));
    }
  if ! consteval        // { dg-warning "'if consteval' only available with=
" ""
{ target c++20_only } }
    {
      r +=3D foo (32 * baz (0));
    }
  if consteval          // { dg-warning "'if consteval' only available with=
" ""
{ target c++20_only } }
    {
      r +=3D 32 * bar ();
    }
  return r;
}

This one is valid, but before your r12-7264 was incorrectly rejected becaus=
e 8
* baz (0) etc. is wrapped in NON_DEPENDENT_EXPR,
potential_constant_expression_1 recursed on the NON_DEPENDENT_EXPR operand,
found it is ok but cxx_eval_constant_expression
rejected the NON_DEPENDENT_EXPR.  Bet for the build_over_call
processing_template_decl immediate_invocation_p code we need to punt silent=
ly
if there is something we can't handle but fail loudly if we can handle
everything but it is clearly always not a constant expression.=20
potential_constant_expression_1 isn't 100% accurate, there are cases where =
it
gets stuff through.=