[ruby-core:28936] [Bug #1393] Multiple assignment does not call to_a but to_ary

Issue #1393 has been updated by Yusuke Endoh.

Category set to core
Assigned to changed from Koichi Sasada to Yukihiro Matsumoto

Hi,

2009/4/21 Vincent Isambart <[e-mail]>:
> In Ruby 1.9, when Ruby is expecting an array and does not get one (for example in splat arguments), it calls the to_a method on the object.
> For example, if x is not an array, "y = *x" tries to call x.to_a.
> However, in multiple assignments, it does not try to call to_a but to_ary.
> For example, "*y = x" tries to call x.to_ary.

This issue is still reproducable:

  obj = Object.new
  def obj.to_a; [1, 2]; end
  def obj.to_ary; [3, 4]; end
  def foo(x, y); p [x, y]; end

  a, b = *obj; p [a, b]  #=> [1, 2] on 1.9, [3, 4] on 1.8
  foo(*obj)              #=> [1, 2] on 1.9, [3, 4] on 1.8


> Should not Ruby try to call to_a in both cases? It looks like a bug to me.

Agreed.  I think that to_ary should be called because the both cases do
implicit conversion.


> Is there a particular reason this was done?

I guess that it is just a slip-up when removing to_splat (r14063).

Matz, is my guess correct?
Yugui, do you allow the spec change (fix) in 1.9.2?


FYI: if this is fixed, 21 failures/errors occur on RubySpec.
They depend on the current behavior implicitly and explicitly, such as:

  [*nil].should == []

  a = loop do break *nil; end; a.should == []

  obj = Object.new
  def obj.to_a
    [1, 2]
  end
  return *obj

-- 
Yusuke ENDOH <[e-mail]>
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