Bug #9898: Keyword argument oddities

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-darwin13.0]
• Backport: 2.0.0: DONTNEED, 2.1: DONE

[brixen (Brian Shirai)]

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?

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)
• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN to 2.0.0: DONTNEED, 2.1: REQUIRED

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

Applied in changeset r46342.

---

vm.c: return the result hash

• vm.c (core_hash_merge_kwd): should return the result hash, which
  may be converted from and differ from the given argument.
  [ruby-core:62921] [Bug #9898]

[nobu (Nobuyoshi Nakada)]

• Has duplicate Bug #9954: Unexpected Hash Modification and Segmentation Fault with Named Arguments added

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: DONTNEED, 2.1: REQUIRED to 2.0.0: DONTNEED, 2.1: DONE

Backported into ruby_2_1 at r46619.

[hsbt (Hiroshi SHIBATA)]

• Related to Feature #14183: "Real" keyword argument added