Issue #9898 has been reported by Brian Shirai.

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Bug #9898: Keyword argument oddities
https://bugs.ruby-lang.org/issues/9898

* Author: Brian Shirai
* Status: Open
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
* ruby -v: ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-darwin13.0]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
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Case 1: If a method takes a single argument, and the method is called with a keyword splat, the method receives the passed object, not the result of calling #to_hash on the object:

# kw1.rb
def m(a) a end
o = Object.new
def o.to_hash() puts "to_hash"; { a: 1 } end
p m(**o)

$ ruby -v kw1.rb
ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-darwin13.0]
to_hash
#<Object:0x007fdee188ab90>

Would someone please explain why the result of #to_hash in not passed to the method?


Case 2: If the method takes a keyword argument, #to_hash is called at the send site and at the receiver:

# kw2.rb
def mk(a:) a end
o = Object.new
def o.to_hash() puts "to_hash"; { a: 1 } end
p mk(**o)

$ ruby -v kw2.rb
ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-darwin13.0]
to_hash
to_hash
1

Would someone please explain why #to_hash is called at both the send site and at the receiver?





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