On Wed, May 30, 2012 at 2:37 PM, Henrik Sperre Johansen <henrik.s.johansen@veloxit.no> wrote:

On 30.05.2012 14:05, Mariano Martinez Peck wrote:

Hi guys. I found a problem while working with FuelPreview where we store objects of the graph in a Set. While doing a collect, there was an error because an implementation of #= was assuming that the argument was of a certain shape. Of course, that should answer false instead. So I wrote this test to see all existing wrong implementations:

testAllClassesImplementSafeEqualsMethod
"This tests that all classes in the system that implements #= do it in a way that they don't throw error when passing as an argument something different from expected. The correct behavior is that #= answers false."
�� | wrongClasses |
�� wrongClasses := IdentityDictionary ��new.
�� ((SystemNavigation default allImplementorsOf: #=)
�� collect: [:each | each methodClass])
�� do: [:each |
�� | instance |
�� "Some classes like CompiledMethod override basicNew to throw an error.
�� In any case, the comparison will be false, so no problem"
�� [instance := each basicNew] on: Error do: [].
�� [instance = Object new]
�� on: Error
�� do: [: err | wrongClasses at: each put: err ]].
�� self assert: wrongClasses isEmpty

The result is: {Magnitude. WideCharacterSet. KMKeymap. MCMockDefinition. ScaledDecimal. MCSnapshot}

So, my I think we should change #= in those classes by adding:

�� self == aKeymap
�� ifTrue: [ ^ true ].
�� self class = aKeymap class
�� ifFalse: [ ^ false ].

at the beginning of the #=

what do you think? ��if agree, I open an issue.

--
Mariano
http://marianopeck.wordpress.com

I'd test against self species rather than self class, since it gives greater flexibility for user-defined instances to potentially = classes in the system.

In other word, #class has a very strict meaning which would hinder extensibility, #species less so.

Ok, I see. But the classes are only a few (five). So you recommend you use self species instead of self class even if we "analyze" those 5 classes to see if it is worth it or not (for example, we check if they do override #species or not) ?