[Pharo-dev] IndexedSlots in combination with StatefulTraits

[Torsten Bergmann]

I guess I found a bug in accessing Slots using #slots in combination with 
IndexedSlots and traits.
To reproduce use latest Pharo 7 (Build 1126)

First create a class with a slot, note that the slot needs to be :

Object subclass: #ClassA
        slots: { IndexedSlot named: #upper }
        classVariables: { }
        package: 'Slot-Bugs'

As it is the first slot it internally receives an index 1 as you can check with 
"ClassA slots first".

Now define a stateful trait with another indexed slot:
        
        Trait named: #StatefulTrait
                uses: {}
                slots: { IndexedSlot named: #slotFromTrait }
                category: 'Slot-Bugs'   
         
And create a new subclass using the new Trait

        ClassA subclass: #ClassB
                uses: StatefulTrait
                instanceVariableNames: ''
                classVariableNames: ''
                package: 'Slot-Bugs'     
         

1. when you evaluate "ClassA slots"  it returns {#FirstSlot => Slot} which is 
correct
2. when you evaluate "StatefulTrait slots"  it returns {#slotFromTrait => Slot} 
which is correct
3. when you evaluate "ClassB allSlots"  returns  "an OrderedCollection(#upper 
=> InstanceVariableSlot #slotFromTrait => InstanceVariableSlot)" which is OK

but  

4. when you evaluate "ClassB slots" it returns  {#slotFromTrait => 
InstanceVariableSlot} which is NOT correct as class B does not define the slot, 
it is defined in the trait

         
So I think 4. is wrong and reasons is the implementation of #slot:

  slots
        "I remove the slots comming from a traitComposition"
        ^ super slots reject:[ :e  | self traitComposition slots includes:e ]   
 
        
If you debug you will notice that 

   super slots                   returns our #slotFromTrait with an index of 2 
while 
   self traitComposition slots   returns our #slotFromTrait with an index of 1 
while 

which is the same #slotFromTrait but a different index - therefore it does not 
get removed.

 
Dont know what is the best way to fix this without any side effects. Commenst 
and help appreciated. 

Thanks
T.