Ruby

When using class_eval with a proc, references to class variables scoped to the receiver in 1.9.2, but in 1.9.3 class variables are now lexically scoped to the environment of the proc. For example, this code:

class Foo def initialize @@value = "Set from Foo initialize" end def report @@value end end class Bar def initialize @@value = "Set from Bar initialize" end def report @@value end def monkey Foo.class_eval do def set(value) @@value = value end end end end b = Bar.new b.monkey f = Foo.new puts "Before monkeying:" puts "Bar's class var: #{b.report}" puts "Foo's class var: #{f.report}" f.set("Set through Monkey") puts "After monkeying:" puts "Bar's class var: #{b.report}" puts "Foo's class var: #{f.report}" 

Running under 1.9.2-p290:

Before monkeying: Bar's class var: Set from Bar initialize Foo's class var: Set from Foo initialize After monkeying: Bar's class var: Set from Bar initialize Foo's class var: Set through Monkey 

Running under 1.9.3-p0:

Before monkeying: Bar's class var: Set from Bar initialize Foo's class var: Set from Foo initialize After monkeying: Bar's class var: Set through Monkey Foo's class var: Set from Foo initialize