Add TARGET_EXPR_DIRECT_INIT_P sanity check.

	* cp-gimplify.c (cp_gimplify_expr) [TARGET_EXPR]: Check
	TARGET_EXPR_DIRECT_INIT_P.
	* constexpr.c (cxx_eval_constant_expression): Likewise.

From-SVN: r280019

gcc/cp/ChangeLog

 2020-01-08  Jason Merrill  <jason@redhat.com>
 
+	* cp-gimplify.c (cp_gimplify_expr) [TARGET_EXPR]: Check
+	TARGET_EXPR_DIRECT_INIT_P.
+	* constexpr.c (cxx_eval_constant_expression): Likewise.
+
+2020-01-08  Jason Merrill  <jason@redhat.com>
+
 	PR c++/91369 - constexpr destructor and member initializer.
 	* constexpr.c (cxx_eval_store_expression): Look through TARGET_EXPR
 	when not preevaluating.

gcc/cp/constexpr.c

@@ -5312,6 +5312,7 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
 	  *non_constant_p = true;
 	  break;
 	}
+      gcc_checking_assert (!TARGET_EXPR_DIRECT_INIT_P (t));
       /* Avoid evaluating a TARGET_EXPR more than once.  */
       if (tree *p = ctx->global->values.get (TARGET_EXPR_SLOT (t)))
 	{

gcc/cp/cp-gimplify.c

@@ -925,6 +925,13 @@ cp_gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
 	}
       break;
 
+    case TARGET_EXPR:
+      /* A TARGET_EXPR that expresses direct-initialization should have been
+	 elided by cp_gimplify_init_expr.  */
+      gcc_checking_assert (!TARGET_EXPR_DIRECT_INIT_P (*expr_p));
+      ret = GS_UNHANDLED;
+      break;
+
     case RETURN_EXPR:
       if (TREE_OPERAND (*expr_p, 0)
 	  && (TREE_CODE (TREE_OPERAND (*expr_p, 0)) == INIT_EXPR