The class variables are kept (declared), even if explicitly removed.
It is ok? (i.e. the messages are not recompiled.)
I had expected either a forced recompilation of the class messages
(while removing the class variable), or a run time error.
Patrick Chénais
Procedure:
......................................................
1. Create a new Class ->
Object subclass: #MyFirstClass
 instanceVariableNames: 'alpha'
 classVariableNames: ''
 poolDictionaries: ''
 category: 'Patrick-Nodes'
......................................................
2. Create new messages in category accessing ->
alpha: aNumber
 alpha := aNumber
alpha
 ^ alpha
......................................................
3. Try it ->
x := MyFirstClass new alpha: 12.
x alpha 12 (Print)
x beta (Print) MessageNotUnderstood: MyFirstClass>>beta
UNTIL NOW, ALL WORK VERY FINE... :))
......................................................
But
......................................................
4. Now remove Variable alpha
Object subclass: #MyFirstClass
 instanceVariableNames: ''
 classVariableNames: ''
 poolDictionaries: ''
 category: 'Patrick-Nodes'
......................................................
4. Try it  ->
x := MyFirstClass new alpha: 24.
x alpha 24 (Print)
Works also fine, but wrong :( because variable alpha does not exist
anymore. It should provoke a run time error, isn't it?

It's gone to Undeclared.
If you do
 Undeclared removeUnreferencedKeys; inspect
you'll see it.
When you remove a *class* variable that is still used by code, you get
a dialog asking you if it is OK to move it to Undeclared.
But you don't see that prompt with an instance variable.
If you select that variable name in your code and choose 'explain' from
the context menu, it should explain where it went.
alpha "is an undeclared variable."
SystemNavigation browseAllCallsOn: (Undeclared associationAt: #alpha).
Unfortunately, this explanation of how to see it is wrong. It should be
SystemNavigation new browseAllCallsOn: (Undeclared associationAt:
#alpha).