c++: constexpr VEC_INIT_EXPR [PR118285]

cxx_eval_vec_init_1 was doing the wrong thing for an array of
self-referential class type; just evaluating the TARGET_EXPR initializer
creates a new object that refers to the TARGET_EXPR_SLOT, if we want it to
refer properly to the initialization target we need to provide it.

	PR c++/118285

gcc/cp/ChangeLog:

	* constexpr.cc (cxx_eval_vec_init_1): Build INIT_EXPR for
	initializing a class.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/initlist-opt7.C: New test.

1 files changed, 41 insertions, 0 deletions

diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-opt7.C b/gcc/testsuite/g++.dg/cpp0x/initlist-opt7.C
new file mode 100644
index 0000000..f55ef5b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist-opt7.C
@@ -0,0 +1,41 @@
+// PR c++/118285
+// { dg-do compile { target c++20 } }
+
+#include <initializer_list>
+
+struct A {
+  char *a;
+  union { char b[8]; long c; };
+  constexpr A (const char *x) : a(b)
+  {
+    for (int i = 0; i < 8; ++i)
+      b[i] = 0;
+  }
+  constexpr ~A ()
+  {
+    if (!foo ())
+      bar (c);
+  }
+  constexpr bool foo ()
+  {
+    char *x = a;
+    if (x == b)
+      return true;
+    return false;
+  }
+  constexpr void bar (long) {}
+};
+
+constexpr void
+baz (std::initializer_list<A>)
+{
+}
+
+constexpr bool
+qux ()
+{
+  baz ({""});
+  return true;
+}
+
+static_assert (qux (), "");