Issue #16993 has been updated by Dan0042 (Daniel DeLorme). mame (Yusuke Endoh) wrote in #note-9:

Given the convention of deriving methods such as `key_set` from `keys`, where the former returns a set instead of an array, one might expect a corresponding derivation like `Kernel#instance_variable_set` for `Kernel#instance_variables`. Unfortunately, this would conflict with an existing method name.

In https://github.com/ruby/set/pull/40 the name was changed to #keys_to_set, so this comment doesn't apply anymore. Then again I wish all optimizations like this could be implemented at the VM level, so that `hash.keys.to_set` would automatically be efficient rather than having to explicitly use the efficient version #keys_to_set. ---------------------------------------- Feature #16993: Sets: from hash keys using Hash#key_set https://bugs.ruby-lang.org/issues/16993#change-112642 * Author: marcandre (Marc-Andre Lafortune) * Status: Open ---------------------------------------- To create a set from hash keys currently implies a temporary array for all keys, rehashing all those keys and rebuilding a hash. Instead, the hash could be copied and its values set to `true`. ```ruby h = {a: 1} # Now: Set.new(h.keys) # => Set[:a] # After h.key_set # => Set[:a], efficiently. ``` -- https://bugs.ruby-lang.org/