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  <pola...@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