Changes between Initial Version and Version 1 of Ticket #13153, comment 6


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Timestamp:
Jan 20, 2017 5:24:30 AM (3 years ago)
Author:
nomeata
Comment:

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  • Ticket #13153, comment 6

    initial v1  
    1 The `fmap` in
    2 {{{
    3 instance Traversable ZipList where
    4   traverse f (ZipList xs) = ZipList <$> traverse f xs
    5 }}}
    6 is not polymorphic, but rather a concret one (the one from `Functor []`), right? I would expect that to be resolved to actual `map`, for which we have a `map/coerce` rule, which should optimize the whole `ZipLib <$>` stuff away.
     1--deleted--
    72
    8 Did you check the core if there is really an `fmap` or `map` left? If so, then the rules don't work as expected, and that is a bug.
     3(I thought for a moment the problematic `<$>` was `[]`’s, where rule should optimize this away, but that is not the case.)