c++: Fix ICE in reshape_init with init-list [PR95164]

This patch fixes a long-standing bug in reshape_init_r.  Since r209314
we implement DR 1467 which handles list-initialization with a single
initializer of the same type as the target.  In this test this causes
a crash in reshape_init_r when we're processing a constructor that has
undergone the DR 1467 transformation.

Take e.g. the

  foo({{1, {H{k}}}});

line in the attached test.  {H{k}} initializes the field b of H in I.
H{k} is a functional cast, so has TREE_HAS_CONSTRUCTOR set, so is
COMPOUND_LITERAL_P.  We perform the DR 1467 transformation and turn
{H{k}} into H{k}.  Then we attempt to reshape H{k} again and since
first_initializer_p is null and it's COMPOUND_LITERAL_P, we go here:

           else if (COMPOUND_LITERAL_P (stripped_init))
             gcc_assert (!BRACE_ENCLOSED_INITIALIZER_P (stripped_init));

then complain about the missing braces, go to reshape_init_class and ICE
on
               gcc_checking_assert (d->cur->index
                                    == get_class_binding (type, id));

because due to the missing { } we're looking for 'b' in H, but that's
not found.

So we have to be prepared to handle an initializer whose outer braces
have been removed due to DR 1467.

gcc/cp/ChangeLog:

	PR c++/95164
	* decl.c (reshape_init_r): When initializing an aggregate member
	with an initializer from an initializer-list, also consider
	COMPOUND_LITERAL_P.

gcc/testsuite/ChangeLog:

	PR c++/95164
	* g++.dg/cpp0x/initlist123.C: New test.

2 files changed, 40 insertions, 1 deletions

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 31d6874..ca1c8a4 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -6466,7 +6466,7 @@ reshape_init_r (tree type, reshape_iter *d, tree first_initializer_p,
      non-empty subaggregate, brace elision is assumed and the
      initializer is considered for the initialization of the first
      member of the subaggregate.  */
-  if (TREE_CODE (init) != CONSTRUCTOR
+  if ((TREE_CODE (init) != CONSTRUCTOR || COMPOUND_LITERAL_P (init))
       /* But don't try this for the first initializer, since that would be
 	 looking through the outermost braces; A a2 = { a1 }; is not a
 	 valid aggregate initialization.  */
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist123.C b/gcc/testsuite/g++.dg/cpp0x/initlist123.C
new file mode 100644
index 0000000..29f037f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist123.C
@@ -0,0 +1,39 @@
+// PR c++/95164
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wmissing-braces" }
+
+struct H {
+  int a;
+};
+
+struct X : H { };
+
+struct I {
+  int c;
+  H b;
+};
+struct E { I d; };
+void foo(E);
+
+template<int N>
+void fn ()
+{
+  int a = 42;
+  int &k = a;
+
+  foo({1, {H{k}}}); // { dg-warning "missing braces around initializer for .I." }
+  foo({1, {X{k}}}); // { dg-warning "missing braces around initializer for .I." }
+
+  foo({{1, {k}}});
+  foo({{1, {N}}});
+
+  foo({{1, H{k}}});
+  foo({{1, H{N}}});
+  foo({{1, X{k}}});
+  foo({{1, X{N}}});
+
+  foo({{1, {H{k}}}});
+  foo({{1, {H{N}}}});
+  foo({{1, {X{k}}}});
+  foo({{1, {X{N}}}});
+}