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我正在尝试安装最新版本的 Heist，但errors-1.3.1无法安装依赖项。关于如何克服这个问题的任何建议？

$ cabal install errors-1.3.1
Resolving dependencies...
Configuring errors-1.3.1...
Building errors-1.3.1...
Preprocessing library errors-1.3.1...
[1 of 5] Compiling Data.EitherR     ( Data/EitherR.hs, dist/build/Data/EitherR.o )
[2 of 5] Compiling Control.Error.Util ( Control/Error/Util.hs, dist/build/Control/Error/Util.o )

Control/Error/Util.hs:74:10:
    Could not deduce (Monad m) arising from a use of `fmap'
    from the context (Functor m)
      bound by the type signature for
                 fmapRT :: Functor m => (a -> b) -> EitherT l m a -> EitherT l m b
      at Control/Error/Util.hs:74:1-13
    Possible fix:
      add (Monad m) to the context of
        the type signature for
          fmapRT :: Functor m => (a -> b) -> EitherT l m a -> EitherT l m b
    In the expression: fmap
    In an equation for `fmapRT': fmapRT = fmap
cabal: Error: some packages failed to install:
errors-1.3.1 failed during the building phase. The exception was:
ExitFailure 1
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1 回答 1

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我在最新的错误中修复了这个问题，即 1.4.1（1.4.0 有一个错误，我没有导出 EitherT 和 MaybeT 类型）。这次我添加了任一依赖项的上限，以防止它在将来发生。

于 2013-02-10T00:40:43.960 回答