On Sun, 9 Jan 2011, Frank Shearar wrote:

> On 2011/01/09 16:21, Levente Uzonyi wrote:
>> On Sun, 9 Jan 2011, Frank Shearar wrote:
>> 
>>> Hi,
>>> 
>>> I ran into a pair of bugs by accident
>>> (http://bugs.squeak.org/view.php?id=7595 and
>>> http://bugs.squeak.org/view.php?id=7596) that are caused by the same
>>> problem.
>>> 
>>> If you have a MessageNames that shows Undeclared, and you select
>>> Undeclared, you get a pair of walkbacks because code that expects a
>>> class actually gets a Dictionary. The problem stems from Smalltalk
>>> classNamed: #Undeclared returning something that's not actually a
>>> class. (I suspect this kind of bug will manifest for other non-class
>>> globals.)
>>> 
>>> Now one workaround is possibly to turn code like this:
>>> 
>>> selectedClassOrMetaClass
>>> "Answer the currently selected class (or metaclass)."
>>> messageListIndex > 0 ifTrue: [
>>> ^ self setClassAndSelectorIn: [:c :s | ^c]].
>>> (selectorListIndex isNil not and: [selectorListIndex > 0]) ifTrue:
>>> [^Smalltalk classNamed: (self selectorList at: selectorListIndex)].
>>> ^ nil.
>>> 
>>> into something like this:
>>> 
>>> selectedClassOrMetaClass
>>> "Answer the currently selected class (or metaclass)."
>>> messageListIndex > 0 ifTrue: [
>>> ^ self setClassAndSelectorIn: [:c :s | ^c]].
>>> (selectorListIndex isNil not and: [selectorListIndex > 0]) ifTrue:
>>> [ | cls |
>>> cls := Smalltalk classNamed: (self selectorList at: selectorListIndex).
>>> ^(cls isKindOf: Behavior) ifTrue: [cls]].
>>> ^ nil.
>>> 
>>> I dislike this. You'd have to check the result of #classNamed: for
>>> being a class!
>>> 
>>> I'd rather fix the underlying problem, and change
>>> SystemDictionary>>classOrTraitNamed: so that the last clause said
>>> something like
>>> 
>>> baseClass := Smalltalk at: baseName asSymbol ifAbsent: [^ nil].
>>> meta
>>> ifTrue: [^ baseClass classSide]
>>> ifFalse: [^ (baseClass isKindOf: Behavior) ifTrue: [baseClass]]
>>> 
>>> That doesn't seem to smash up anything, but is the above _sane_?
>> 
>> It's an old idea to ensure that #classNamed: returns a class (or maybe a
>> trait), but I'm not sure it won't break anything.
>> I think it would be better to write it like this:
>> 
>> ^self at: baseName asSymbol ifPresent: [ :global |
>> global isBehavior ifTrue: [
>> meta
>> ifFalse: [ global ]
>> ifTrue: [ global classSide ] ] ]
>
> I'll prepare an MCZ with tests, in the meantime, and try bang on the change.

Thanks.

>
> It looks like System currently has two heads in trunk - System-bp.408 and 
> System-dtl.408. With a freshly updated trunk image, it thus looks like there 
> are local changes to the image before I've done anything.

Right, Chris forgot to merge the two versions when he pushed 
System-bp.408.


Levente

>
> frank
>
>