Make sure boolbv::get returns tag types when requested

boolbv::get should return expressions of exactly the same type, not an expanded
version of the type.

Author: tautschnig

src/solvers/flattening/boolbv_get.cpp

@@ -120,15 +120,19 @@ exprt boolbvt::bv_get_rec(
     }
     else if(type.id()==ID_struct_tag)
     {
-      return
+      exprt result=
         bv_get_rec(
           bv, unknown, offset, ns.follow_tag(to_struct_tag_type(type)));
+      result.type() = type;
+      return std::move(result);
     }
     else if(type.id()==ID_union_tag)
     {
-      return
+      exprt result=
         bv_get_rec(
           bv, unknown, offset, ns.follow_tag(to_union_tag_type(type)));
+      result.type() = type;
+      return std::move(result);
     }
     else if(type.id()==ID_struct)
     {