[Bug #17767] Now ENV.clone raises TypeError as well as ENV.dup
One year ago, the former method has been deprecated while the latter has become an error. Then the 3.1 released, it is enough time to make also the former an error.
Related issues
Bug #17767: `Cloned ENV` inconsistently returns `ENV` or `self`
Added by nobu (Nobuyoshi Nakada) over 3 years ago
[Bug #17767] Now
ENV.cloneraisesTypeErroras well asENV.dupOne year ago, the former method has been deprecated while the latter
has become an error. Then the 3.1 released, it is enough time to make
also the former an error.