我今天早上尝试安装几个模块以使Eclipse FP正常工作，scion-browser和buildwrapper失败。
[root@localhost ghc-mod]# cabal install scion-browser
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: scion-browser-0.3.0
[root@localhost ghc-mod]# cabal install buildwrapper
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: buildwrapper-0.8.0
我简短地继续#haskell IRC，但无法得到答案，但我没有在IRC中长时间闲逛。然后我放弃了EclipseFP并与vim一起走上了快乐的道路。我之前使用过vim用于其他语言，我认为即使我可能没有调试器也会很好。但好奇心让我安装了一些插件，可以增强我在haskell中的编码体验，但是其中一个插件需要ghc-mod，所以我想我会再次给cabal install。我最终得到了以下错误。
[root@localhost ghc-mod]# cabal install ghc-mod
Resolving dependencies...
Configuring ghc-mod-0.3.0...
Building ghc-mod-0.3.0...
Preprocessing executable 'ghc-mod' for ghc-mod-0.3.0...
[1 of 6] Compiling Param ( Param.hs, dist/build/ghc-mod/ghc-mod-tmp/Param.o )
[2 of 6] Compiling Lang ( Lang.hs, dist/build/ghc-mod/ghc-mod-tmp/Lang.o )
[3 of 6] Compiling List ( List.hs, dist/build/ghc-mod/ghc-mod-tmp/List.o )
[4 of 6] Compiling Check ( Check.hs, dist/build/ghc-mod/ghc-mod-tmp/Check.o )
[5 of 6] Compiling Browse ( Browse.hs, dist/build/ghc-mod/ghc-mod-tmp/Browse.o )
Browse.hs:41:72:
Not in scope: data constructor `ExplicitForall'
Perhaps you meant `ExplicitForAll' (imported from Language.Haskell.Exts.Extension)
Failed to install ghc-mod-0.3.0
cabal: Error: some packages failed to install:
ghc-mod-0.3.0 failed during the building phase. The exception was:
ExitFailure 1
我尝试克隆项目然后运行cabal install，最后得到以下结果。
[root@localhost ghc-mod]# cabal install
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: ghc-mod-4.1.0
我真的想深究这个问题。我不确切知道cabal在哪里失败，所以很难找出它正在抱怨的依赖性。接下来是cabal和ghc的版本。
[root@localhost ghc-mod]# cabal --version
cabal-install version 1.16.0.2
using version 1.16.0 of the Cabal library
[root@localhost ghc-mod]#
[root@localhost ghc-mod]# ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.6.3
有人可以帮我理解来自cabal的错误消息吗？如果我错过了一个微不足道的话，我对哈斯克尔来说相对较新，所以道歉。