Bert Freudenberg uploaded a new version of Kernel to project The Trunk:
http://source.squeak.org/trunk/Kernel-bf.565.mcz

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

Name: Kernel-bf.565
Author: bf
Time: 7 April 2011, 12:08:35.536 pm
UUID: f5b1f9f1-3c3b-4dac-bec9-88df9a90cd0e
Ancestors: Kernel-ar.564

- make ObjectTracer/ObjectViewer work again (try the example in ObjectViewer class comment). BEWARE however, sending xxxUnTrace still sometimes locks up the image
- not sure why sentTo: doesn't work, had to switch to sendTo:
- optionally allow accessing the caught message, e.g.:
	object evaluate: [:msg | Transcript cr; show: msg]
		wheneverChangeIn: [x := x = false].

=============== Diff against Kernel-ar.564 ===============

Item was changed:
+ ProtoObject subclass: #ObjectTracer
- nil subclass: #ObjectTracer
  	instanceVariableNames: 'tracedObject recursionFlag'
  	classVariableNames: ''
  	poolDictionaries: ''
  	category: 'Kernel-Objects'!
  
  !ObjectTracer commentStamp: '<historical>' prior: 0!
  An ObjectTracer can be wrapped around another object, and then give you a chance to inspect it whenever it receives messages from the outside.  For instance...
  	(ObjectTracer on: Display) flash: (50 at 50 extent: 50 at 50)
  will give control to a debugger just before the message flash is sent.
  Obviously this facility can be embellished in many useful ways.
  See also the even more perverse subclass, ObjectViewer, and its example.
  !

Item was removed:
- ----- Method: ObjectViewer class>>on:evaluate:wheneverChangeIn: (in category 'instance creation') -----
- on: viewedObject evaluate: block1 wheneverChangeIn: block2
- 	^ self new xxxViewedObject: viewedObject evaluate: block1 wheneverChangeIn: block2!

Item was changed:
  ----- Method: ObjectViewer>>doesNotUnderstand: (in category 'very few messages') -----
  doesNotUnderstand: aMessage 
  	"Check for change after sending aMessage"
  	| returnValue newValue |
+ 	recursionFlag ifTrue: [^ aMessage sendTo: tracedObject].
- 	recursionFlag ifTrue: [^ aMessage sentTo: tracedObject].
  	recursionFlag := true.
+ 	returnValue := aMessage sendTo: tracedObject.
+ 	newValue := valueBlock valueWithPossibleArgument: aMessage.
- 	returnValue := aMessage sentTo: tracedObject.
- 	newValue := valueBlock value.
  	newValue = lastValue ifFalse:
+ 		[changeBlock valueWithPossibleArgument: aMessage..
- 		[changeBlock value.
  		lastValue := newValue].
  	recursionFlag := false.
  	^ returnValue!