Keyword method parameters cannot take a frozen hash

[blanquer]

It seems that Jruby tries to mess (in some way or another) with the parameters hash that is passed to a method. If one passes those named parameters using a true hash, that it is frozen, Jruby complains it cannot modify a frozen hash.

Here's the smallest repro I could get:

class Foo
  def self.test( arg1: "default" )
    puts "arg1: #{arg1.inspect}"
  end
end

normal_args =  {arg1: "normal"}
frozen_args =  {arg1: "frozen"}.freeze

Foo.test( normal_args ) #=> succeeds
Foo.test( frozen_args ) #=> bails out RuntimeError: can't modify frozen Hash

with mri 2.2.0:

arg1: "normal"
arg1: "frozen"

with jruby-head (as of today):

arg1: "normal"
RuntimeError: can't modify frozen Hash
      delete at org/jruby/RubyHash.java:1574
  __script__ at /tmp/test.rb:11

Oh, and BTW, the original error that I saw in my application somehow complained more loudly about it:

BUG: Got exception org.jruby.exceptions.RaiseException: (RuntimeError) can't modify frozen Hash but instr using(0:0) = recv_kw_arg(0, using) is not supposed to be raising exceptions!

For what it's worth.

[enebo]

Our kwarg handling is not dup'ing kwargs hash which leads to issues like this and #2015. We will get this solved for pre2.