Issue #8316 has been updated by nobu (Nobuyoshi Nakada).

Category set to core
Status changed from Open to Assigned
Assignee set to mame (Yusuke Endoh)


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Bug #8316: Can't pass hash to first positional argument; hash interpreted as keyword arguments
https://bugs.ruby-lang.org/issues/8316#change-38858

Author: TylerRick (Tyler Rick)
Status: Assigned
Priority: Normal
Assignee: mame (Yusuke Endoh)
Category: core
Target version: 
ruby -v: ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-linux]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


I'm able to pass any other type of object to my first argument:

 def foo(hash, opt: true)
   puts "hash: #{hash}, opt: #{opt.inspect}"
 end
 
 foo 'a'                 # => hash: a, opt: true
 foo [{a:1}]             # => hash: [{:a=>1}], opt: true
 foo [{a:1}], opt: false # => hash: [{:a=>1}], opt: false

But when I try to pass a hash, it raises an ArgumentError:

 foo({a:1})  # Raises ArgumentError: unknown keyword: a
 # Expected behavior: hash: {:a=>1}, opt: true

I tried to work around the "unknown keyword" error by using ** but ended up getting a "wrong number of arguments (0 for 1)" error instead.

 def foo_with_extra(hash, **extra)
   puts "hash: #{hash}, extra: #{extra.inspect}"
 end
 
 foo_with_extra 'a'                 # hash: a, extra: {}
 foo_with_extra [{a:1}]             # hash: [{:a=>1}], extra: {}
 foo_with_extra [{a:1}], opt: false # hash: [{:a=>1}], extra: {:opt=>false}
 
 foo_with_extra({a:1})  # Raises ArgumentError: wrong number of arguments (0 for 1)
 # Expected behavior: hash: {:a=>1}, extra: {}

This behavior is surprising and I haven't seen it mentioned anywhere before. Is it really intentional?


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