Joshua Gargus uploaded a new version of System to project The Trunk:
http://source.squeak.org/trunk/System-jcg.228.mcz

==================== Summary ====================

Name: System-jcg.228
Author: jcg
Time: 9 January 2010, 2:27:15 am
UUID: f79fe9d8-3dad-4dce-b583-9c20f871819a
Ancestors: System-ar.227

Add PseudoClass>>includesSelector: to patch a MessageNotUnderstood encountered while filing in code from a file.

=============== Diff against System-ar.227 ===============

Item was added:
+ ----- Method: PseudoClass>>includesSelector: (in category 'testing method dictionary') -----
+ includesSelector: aSymbol 
+ 	self exists
+ 		ifTrue: [^self realClass includesSelector: aSymbol]
+ 		ifFalse: [
+ 			"Not sure what the answer should be in this case (I'm unfamiliar with this class),
+ 			 so I want to force an error rather than answer something nonsensical.  This is
+ 			 no worse than the old behavior, when this method didn't even exist, resulting
+ 			 in a MessageNotUnderstood error."
+ 			self error: 'real class does not exist'
+ 		]!