[Bug c++/105321] New: "non-constant condition" issued for function containing a short-circuited unevaluated non-constant expression

["bekenn at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105321

            Bug ID: 105321
           Summary: "non-constant condition" issued for function
                    containing a short-circuited unevaluated non-constant
                    expression
           Product: gcc
           Version: 11.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bekenn at gmail dot com
  Target Milestone: ---

bool handle_error();

constexpr int echo(int value, bool yes = true) noexcept
{
    return (yes || handle_error()), value;
}

static_assert(echo(10) == 10, "");

---

<source>:8:24: error: non-constant condition for static assertion
    8 | static_assert(echo(10) == 10, "");
      |               ~~~~~~~~~^~~~~
<source>:8:19:   in 'constexpr' expansion of 'echo(10, 1)'
<source>:3:36: error: 'yes' is not a constant expression
    3 | constexpr int echo(int value, bool yes = true) noexcept
      |                               ~~~~~^~~~~~~~~~

https://godbolt.org/z/vsd9xdW5c

---

It appears that the || operator isn't short-circuiting correctly during
constant evaluation.  This seems to be very particular; if I replace `yes` with
a more complicated expression (such as `!no`), the problem disappears.

This issue shows up in every version of GCC I've tried, including 11.2 and the
current "trunk" release on Compiler Explorer.