C++ PATCH for c++/71638, ICE with NSDMI and reference

[Marek Polacek]

This extends my previous fix for c++/84927 in that it also updates
the ctor's flags when we replace an element.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2018-03-20  Marek Polacek  <polacek@redhat.com>

	PR c++/71638, ICE with NSDMI and reference.
	* constexpr.c (cxx_eval_bare_aggregate): Update constructor's flags
	even when we replace an element.

	* g++.dg/cpp0x/nsdmi14.C: New test.
	* g++.dg/cpp1y/nsdmi-aggr10.C: New test.

diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c
index 894bcd0bb3e..e2d66498a66 100644
--- gcc/cp/constexpr.c
+++ gcc/cp/constexpr.c
@@ -2873,16 +2873,17 @@ cxx_eval_bare_aggregate (const constexpr_ctx *ctx, tree t,
 	  gcc_assert (is_empty_class (TREE_TYPE (TREE_TYPE (index))));
 	  changed = true;
 	}
-      else if (new_ctx.ctor != ctx->ctor)
-	{
-	  /* We appended this element above; update the value.  */
-	  gcc_assert ((*p)->last().index == index);
-	  (*p)->last().value = elt;
-	}
       else
 	{
-	  CONSTRUCTOR_APPEND_ELT (*p, index, elt);
-	  /* Adding an element might change the ctor's flags.  */
+	  if (new_ctx.ctor != ctx->ctor)
+	    {
+	      /* We appended this element above; update the value.  */
+	      gcc_assert ((*p)->last().index == index);
+	      (*p)->last().value = elt;
+	    }
+	  else
+	    CONSTRUCTOR_APPEND_ELT (*p, index, elt);
+	  /* Adding or replacing an element might change the ctor's flags.  */
 	  TREE_CONSTANT (ctx->ctor) = constant_p;
 	  TREE_SIDE_EFFECTS (ctx->ctor) = side_effects_p;
 	}
diff --git gcc/testsuite/g++.dg/cpp0x/nsdmi14.C gcc/testsuite/g++.dg/cpp0x/nsdmi14.C
index e69de29bb2d..aac6fa1c81b 100644
--- gcc/testsuite/g++.dg/cpp0x/nsdmi14.C
+++ gcc/testsuite/g++.dg/cpp0x/nsdmi14.C
@@ -0,0 +1,19 @@
+// PR c++/71638
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wall" }
+
+struct A {
+  struct {
+    int i;
+    int &j = i;
+  } b;
+  int a = b.j;
+};
+
+void bar (A);
+
+void
+foo ()
+{
+  bar (A{});
+}
diff --git gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr10.C gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr10.C
index e69de29bb2d..1dc396d9ca5 100644
--- gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr10.C
+++ gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr10.C
@@ -0,0 +1,7 @@
+// PR c++/71638
+// { dg-do compile { target c++14 } }
+
+struct {
+  int &&a;
+  int b{a};
+} c[] { { 2 } };

	Marek