tolerate two cases of imprecision in value_set_fi; addresses issue #2653

Author: Daniel Kroening

src/pointer-analysis/value_set_fi.cpp

@@ -409,13 +409,13 @@ void value_set_fit::get_value_set_rec(
 
     const typet &type=ns.follow(expr.op0().type());
 
-    DATA_INVARIANT(type.id()==ID_array ||
-                   type.id()==ID_incomplete_array ||
-                   type.id()=="#REF#",
-                   "operand 0 of index expression must be an array");
-
-    get_value_set_rec(expr.op0(), dest, "[]"+suffix,
-                      original_type, ns, recursion_set);
+    if(type.id() == ID_array)
+    {
+      get_value_set_rec(expr.op0(), dest, "[]"+suffix,
+                        original_type, ns, recursion_set);
+    }
+    else
+      insert(dest, exprt(ID_unknown, original_type));
 
     return;
   }
@@ -1328,9 +1328,10 @@ void value_set_fit::assign_rec(
 
     assign_rec(typecast_expr.op(), values_rhs, suffix, ns, recursion_set);
   }
-  else if(lhs.id()=="zero_string" ||
-          lhs.id()=="is_zero_string" ||
-          lhs.id()=="zero_string_length")
+  else if(lhs.id() == "zero_string" ||
+          lhs.id() == "is_zero_string" ||
+          lhs.id() == "zero_string_length" ||
+          lhs.id() == ID_address_of)
   {
     // ignore
   }