Allocate objects: cast when pointer types differ

It already tried to do this, but doesn't take account for pointers that encode generic information:
in such cases the underlying object type can be equal but the pointers differ, and a cast is necessary.

Author: smowton

src/util/allocate_objects.cpp

@@ -212,12 +212,8 @@ exprt allocate_objectst::allocate_non_dynamic_object(
   aux_symbol.is_static_lifetime = static_lifetime;
   symbols_created.push_back(&aux_symbol);
 
-  exprt aoe =
-    ns.follow(aux_symbol.symbol_expr().type()) !=
-        ns.follow(target_expr.type().subtype())
-      ? (exprt)typecast_exprt(
-          address_of_exprt(aux_symbol.symbol_expr()), target_expr.type())
-      : address_of_exprt(aux_symbol.symbol_expr());
+  exprt aoe = typecast_exprt::conditional_cast(
+    address_of_exprt(aux_symbol.symbol_expr()), target_expr.type());
 
   code_assignt code(target_expr, aoe);
   code.add_source_location() = source_location;