[ruby-core:68923] [Ruby trunk - Bug #11074] [Open] Block with optional parameter of same closure variable name

Issue #11074 has been reported by Charlton Wang.

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Bug #11074: Block with optional parameter of same closure variable name
https://bugs.ruby-lang.org/issues/11074

* Author: Charlton Wang
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.1.1p76 (2014-02-24 revision 45161) [x86_64-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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~~~
def bar
   yield
end
x = 3
bar do |x=x|
  x
end
=> nil
bar do |y=x|
  x
end
=> 3
~~~
So perhaps x=x isn't able to distinguish that the RHS should probably be the closure x and, instead, is take to mean the value of the (new and uninitialized) x parameter of the block. But then:

~~~
def foo(x=x)
   x
end
foo(3)
=> 3
foo
=> NameError: undefined local variable or method `x' for main:Object
~~~
So at least in this case, it knows that x on the RHS isn't the parameter variable x. This seems a bit inconsistent.

One can get some really odd results as well:

~~~
def foo(x)
   bar do |x=x|
      x
   end
end
foo(1)
=> 491
foo(1)
=> 498
foo(1)
=> 505
~~~
In this case, x=x doesn't render nil as in the previous case. The value of x being returned always increases by 7. Is doing something like x=x as a parameter (to a block) generally viewed as being "undefined" behaviour?

Thanks,
Charlton




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