#2953: deriving Functor, Foldable, Traversable
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Reporter: twanvl | Owner: twanvl
Type: feature request | Status: new
Priority: normal | Milestone: 6.12 branch
Component: Compiler | Version: 6.11
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Os: Unknown/Multiple
Architecture: Unknown/Multiple |
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Comment (by igloo):
If we did that then it wouldn't be clear what a Cabal file saying it needs
the `DeriveExtraClasses` extension actually meant. Would using ghc 6.10.1
be OK (only derives `Data`), would you need 6.12.1 (also derives
`Functor`), or even 6.14.1 (derives something that isn't implemented yet).
I don't know if cabal-install does this yet, but part of the plan was that
if you told it to install a package `foo`, and `foo` needed an extension
that your compiler doesn't support, then cabal-install would fail
immediately, rather than downloading and building all of `foo`'s
dependencies first.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2953#comment:11>
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