fix: some analysis stage problems

tests/programs/pos_method_call_via_field.fzs

@@ -0,0 +1,19 @@
+class Node
+{
+  Node next;
+
+  fn ping()
+  {
+    printline("ping");
+  }
+
+  fn pingNext()
+  {
+    this.next.ping();
+  }
+}
+
+Node head = new Node;
+Node tail = new Node;
+head.next = tail;
+head.pingNext();