Do not use nil_typet in c_bit_field_replacement_type

No caller handles that case, instead insert appropriate PRECONDITIONs.

src/solvers/flattening/c_bit_field_replacement_type.cpp

@@ -6,9 +6,10 @@ Author: Daniel Kroening, [email protected]
 
 \*******************************************************************/
 
-
 #include "c_bit_field_replacement_type.h"
 
+#include <util/invariant.h>
+
 typet c_bit_field_replacement_type(
   const c_bit_field_typet &src,
   const namespacet &ns)
@@ -23,21 +24,18 @@ typet c_bit_field_replacement_type(
     result.set_width(src.get_width());
     return std::move(result);
   }
-  else if(subtype.id()==ID_c_enum_tag)
+  else
   {
+    PRECONDITION(subtype.id() == ID_c_enum_tag);
+
     const typet &sub_subtype=
       ns.follow_tag(to_c_enum_tag_type(subtype)).subtype();
 
-    if(sub_subtype.id()==ID_signedbv ||
-       sub_subtype.id()==ID_unsignedbv)
-    {
-      bitvector_typet result=to_bitvector_type(sub_subtype);
-      result.set_width(src.get_width());
-      return std::move(result);
-    }
-    else
-      return nil_typet();
+    PRECONDITION(
+      sub_subtype.id() == ID_signedbv || sub_subtype.id() == ID_unsignedbv);
+
+    bitvector_typet result = to_bitvector_type(sub_subtype);
+    result.set_width(src.get_width());
+    return std::move(result);
   }
-  else
-    return nil_typet();
 }