test case for bug #78431.

svn path=/trunk/mono/; revision=71284

mono/tests/Makefile.am

@@ -270,6 +270,7 @@ TEST_IL_SRC=			\
 TEST_CS2_SRC = \
 	interlocked-2.2.cs	\
 	pinvoke-2.2.cs 		\
+	bug-78431.2.cs 		\
 	bug-79684.2.cs 		\
 	catch-generics.2.cs	\
 	event-get.2.cs		\

mono/tests/bug-78431.2.cs

@@ -0,0 +1,32 @@
+  public class Pair <T> { 
+    public T fst; 
+    public T snd; 
+  }
+
+  public class RList <T>  {
+    public class Nil : RList <T> {}
+    public class Zero : RList <T> { 
+      public RList <Pair <T> > arg;
+    }
+
+    static int _Length (RList <T> xs) {
+      if (xs is Zero)
+        return RList <Pair <T> >._Length (((Zero)xs).arg);
+      else
+        return 0;
+    }
+    public int Length  {
+      get { 
+        return _Length (this);
+      }
+    }    
+  }
+
+
+class M { 
+  public static void Main() {
+    int x = (new RList<object>.Nil()).Length;
+  }
+}
+
+