* constexpr.c (cxx_eval_switch_expr): Use SWITCH_COND and SWITCH_BODY.
	(cxx_eval_constant_expression) <case COND_EXPR>: Don't look for the
	label in the else branch if we found it in the then branch.

	* g++.dg/cpp1y/constexpr-88983.C: New test.

From-SVN: r268438