| X is a variable | instantiation_error | |
| X is neither an FD variable nor an integer | type_error(fd_variable, X) | |
| N is neither a variable nor an integer | type_error(integer, N) | |
| an element E of the Vars list is neither a variable nor an FD variable nor an integer | type_error(fd_variable, E) | |
| Values is neither a partial list nor a list | type_error(list, Values) | |
| X is a variable | instantiation_error | |
| X is neither an FD variable nor an integer | type_error(fd_variable, X) | |