[Pharo-project] About little magic to support understanding

Hi I wanted to see what is used in Morph so I did the following Define a subclass of ProtoObject and redefnied DNU as follow doesNotUnderstand: aMessage | sel category | sel := aMessage selector. Transcript show: 'Does not understand ', aMessage selector printString ; cr. category := (Morph organization categoryOfElement: sel). self class compile: (Morph sourceCodeAt: sel) classified: category. ^ aMessage sentTo: self. It works if I copy from Object but not from Morph does any of you have an idea.