Bug #19257: Data that defines a member called hash

• Status: Feedback
• Assignee: -
• Target version: -
• ruby -v: ruby 3.2.0 (2022-12-25 revision a528908271) [x86_64-darwin22]
• Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN

[solnic (Peter Solnica)]

I believe this should raise an error given that Data#hash exists as a pre-defined core method and serves a very specific purpose:

data = Data.define(:hash)

obj = data.new(hash: "foo")

obj.hash
# => "foo"

An alternative would be to make obj[:hash] return the value of the member and obj.hash would return the hash of the object, but that could be confusing.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Feedback

Always you can override methods defined in super classes.

class C
end
obj = C.new
p obj.hash #=> an integer

class C
  def hash = "foo"
end
p obj.hash #=> "foo"

No #[] method is a significant difference from Struct.

[ufuk (Ufuk Kayserilioglu)]

While I understand the potential for confusion or a foot-gun, I also agree with @nobu (Nobuyoshi Nakada) that this is in spirit with how Ruby operates, where anything is overridable. Struct has been behaving in the exact same way for years:

irb(main):001:0> Foo = Struct.new(:hash)
=> Foo
irb(main):002:0> Foo.new(42).hash
=> 42
irb(main):003:0> Bar = Struct.new(:bar)
=> Bar
irb(main):004:0> Bar.new(42).hash
=> 4004416633903135689

Having said that, if the proposal was to add a warning for when users override some special methods, like hash or object_id or something, then I would be all for that. A warning for these situations is good enough to warn people who might be doing this by mistake, but is not as drastic as an error preventing them from doing it.