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Trait: Overriden class side methods not added to classes using traits #3158

chisandrei opened this Issue Apr 10, 2019 · 1 comment


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chisandrei commented Apr 10, 2019

The code below creates a trait and adds two class side methods and two instance side methods:

Trait named: #TraitForTest
	 uses: {}
	 category: 'AAA'.
TraitForTest compile: 'ffiLibraryName
	^ 1+1. ' classified: 'test' .
TraitForTest compile: 'anotherMethod
	^ 1+1. ' classified: 'test' .
TraitForTest classTrait compile: 'ffiLibraryName
	^ 2+3. ' classified: 'test' .
TraitForTest classTrait compile: 'anotherMethod
	^ 2+3. ' classified: 'test' .

The class side method #ffiLibraryName is also defined in Object.

When creating then a class using that trait, the class side method #ffiLibraryName is not added to the class.

Object subclass: #ClassWithTrait
	uses: TraitForTest
	instanceVariableNames: ''
	classVariableNames: ''
	package: 'AAA'.

ClassWithTrait ffiLibraryName.

The call to #ffiLibraryName raises an exception as the method defined in Object ends up being called: "'SubclassResponsibility: ClassWithTrait class had the subclass responsibility to implement #ffiLibraryName'".

Running ClassWithTrait anotherMethod. works ok and returns 5.

Checking selectors shows that the method #ffiLibraryName is not added to the class.

ClassWithTrait includesSelector: #ffiLibraryName.  "true"
ClassWithTrait class includesSelector: #ffiLibraryName.  "false"
ClassWithTrait class includesSelector: #anotherMethod.  "true"

TraitForTest includesSelector: #ffiLibraryName. "true"
TraitForTest classTrait includesSelector: #ffiLibraryName.  "true"

Same behaviour in Pharo 7 and 8.


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khinsen commented Apr 11, 2019

I came here to exactly this bug, only to find it reported a day earlier.

There is a potentially useful observation I can add to this. If you remove ffiLibraryName from TraitForTest after defining ClassWithTrait, and then define it again, then ClassWithTrait ffiLibraryName will work as expected. I have been using that as a workaround to continue working on my code.

khinsen added a commit to activepapers/activepapers-pharo that referenced this issue Apr 11, 2019

syrel added a commit to feenkcom/oswindow-glutin that referenced this issue Apr 11, 2019

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