c++: Fix excess precision related ICE on invalid binop [PR107382, PR107383]

c++: Fix excess precision related ICE on invalid binop [PR107382, PR107383]

The following tests ICE in the gcc_assert (common); in cp_build_binary_op.
I've missed that while for * common is set always, while for +, - and /
it is in some cases not.
If it is not, then
  if (!result_type
      && arithmetic_types_p
      && (shorten || common || short_compare))
condition is false, then the following
  if (may_need_excess_precision
      && (orig_type0 != type0 || orig_type1 != type1)
      && build_type == NULL_TREE)
would fail the assertion there and if there wouldn't be excess precision,
  if (code == SPACESHIP_EXPR)
would be false (for SPACESHIP_EXPR we always have build_type set like for
other comparisons) and then trigger
  if (!result_type)
    {
      if (complain & tf_error)
        {
          binary_op_rich_location richloc (location,
                                           orig_op0, orig_op1, true);
          error_at (&richloc,
                    "invalid operands of types %qT and %qT to binary %qO",
                    TREE_TYPE (orig_op0), TREE_TYPE (orig_op1), code);
        }
      return error_mark_node;
    }
So, if result_type is NULL, we don't really need to compute
semantic_result_type because nothing will use it anyway and can get
fall through into the error/return error_mark_node; case.

2022-10-27  Jakub Jelinek  <jakub@redhat.com>

	PR c++/107382
	PR c++/107383
	* typeck.cc (cp_build_binary_op): Don't compute semantic_result_type
	if result_type is NULL.

	* g++.dg/diagnostic/bad-binary-ops2.C: New test.