Do not use hashValue in comparison #44
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Hi @siyusong, |
inamiy
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Feb 24, 2016
Do not use hashValue in comparison
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Hi @inamiy,
First of all, thank you for creating this amazing library!
When exploring the codebase, I found that
hashValues are used in comparison in a few places. This seems a logic error:x == yimpliesx.hashValue == y.hashValue, but not the other way around. Therefore, usinghashValuein comparison, technically speaking, is not reliable because of potential hash collision.I understand that in many cases, we are comparing two hash value generated by SwiftState classes, and hash collision is unlikely/impossible. However, the concrete Event/State types will be implemented by the client (user of SwiftState), so there is no way to guarantee that hash collision won't happen.
I have removed all occurrences of comparison of
hashValues, and reimplemented them using plain old pattern matching. Please let me know your thoughts on this.