[Bug c++/89513] New: constexpr functions with function try block shouldn't be accepted at least with -pedantic in -std=c++{11,14,17} modes

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89513

            Bug ID: 89513
           Summary: constexpr functions with function try block shouldn't
                    be accepted at least with -pedantic in
                    -std=c++{11,14,17} modes
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

With -std=c++{11,14,17} -pedantic-errors we should reject both of these
functions, but we do reject just bar and not foo.  I assume this ought to be
valid C++2a (though wonder if the catch block needs to contain only valid
constexpr constructs even when it is not actually ever evaluated during
constexpr evaluation).

constexpr bool foo ()
try {
  return true;
} catch (...) {
}

constexpr bool bar ()
{
  try { return true; } catch (...) {}
  return true;
}

constexpr auto a = foo ();
constexpr auto b = bar ();