Fixed the bug that a union type containing a struct with a flexible array member was accepted as a struct member or array element type.

test/val/fam.c

@@ -0,0 +1,31 @@
+/* Bug #2016 and #2017 - flexible array members */
+
+typedef struct {
+    int a;
+    int b[];        /* Ok: Flexible array member can be last */
+} X;
+
+typedef union {
+    X   x;          /* Ok: Contains flexible array member */
+    int a;
+} U;
+
+typedef struct {
+    struct {
+        int a;
+    };
+    int b[];    /* Ok: Flexible array member can be last */
+} Y;
+
+X x;
+U u;
+Y y;
+
+_Static_assert(sizeof x == sizeof (int), "sizeof x != sizeof (int)");
+_Static_assert(sizeof u == sizeof (int), "sizeof u != sizeof (int)");
+_Static_assert(sizeof y == sizeof (int), "sizeof y != sizeof (int)");
+
+int main(void)
+{
+    return 0;
+}