map.rb in map-4.7.0

- old
+ new

@@ -1,7 +1,7 @@
 class Map < Hash
-  Version = '4.6.1' unless defined?(Version)
+  Version = '4.7.0' unless defined?(Version)
   Load = Kernel.method(:load) unless defined?(Load)
 
   class << Map
     def version
       Map::Version
@@ -277,14 +277,10 @@
 
   def convert(key, val)
     [convert_key(key), convert_value(val)]
   end
 
-# maps are aggressive with copy operations.  they are all deep copies.  make a
-# new one if you really want a shallow copy
-#
-# TODO - fallback to shallow if objects cannot be marshal'd....
   def copy
     default = self.default
     self.default = nil
     copy = Marshal.load(Marshal.dump(self)) rescue Dup.bind(self).call()
     copy.default = default
@@ -303,9 +299,13 @@
     copy
   end
 
   def default(key = nil)
     key.is_a?(Symbol) && include?(key = key.to_s) ? self[key] : super
+  end
+
+  def default=(value)
+    raise ArgumentError.new("Map doesn't work so well with a non-nil default value!") unless value.nil?
   end
 
 # writer/reader methods
 #
   alias_method '__set__', '[]=' unless method_defined?('__set__')