cabal install ---全局约束需要安装实例 [英] cabal install --- global constraint requires installed instance

问题描述

我的cabal依赖被列为

  base == 4.6。*，containers == 0.5。*，bytestring == 0.10。*，binary == 0.5。*，parsec == 3.1。* 
  

/ p>

  cabal sandbox init 
 wget http://www.stackage.org/lts/cabal.config 
为了克服依赖冲突，我使用沙盒安装。为了克服依赖冲突，我使用了沙箱安装。但是，cabal仍然在谈论一些令我困惑的全局约束。
 
 
 
 Cabal依赖关系树的分辨率被拧紧了， 
 
 
  try：parsec-3.1.8（myproj-0.1.0.0的依赖）
下一个目标：mtl（parsec-3.1.8的依赖）
拒绝：mtl-2.2.1,2.2.0.1,2.2（全局约束需要== 2.1.3.1）
正在尝试：mtl-2.1.3.1 
下一个目标：变换器（依赖于mtl-2.1.3.1 ）
拒绝：变压器-0.4.2.0,0.4.1.0,0.3.0.0,0.2.2.1,0.2.2.0,0.2.1.0，
 0.2.0.0,0.1.4.0,0.1.3.0,0.1 .1.0,0.1.0.1,0.1.0.0,0.0.1.0,0.0.0.0，
 0.4.0.0（全局约束需要安装实例）
  
 
 
解决方案
您应该在当前目录中有一个 cabal.config 文件。使用任何文本编辑器打开它，并为安装的变换器字符串进行搜索。
 
 
 
一旦找到它， 变形金刚== 0.4.3.0 或其他任何你喜欢的版本。
 
My cabal dependencies are listed as
base ==4.6.*, containers ==0.5.*, bytestring ==0.10.*, binary ==0.5.*, parsec ==3.1.*
i did,
cabal sandbox init
wget http://www.stackage.org/lts/cabal.config
cabal install --only-dependencies
To overcome dependency conflicts, i am using sandbox installation. But still, cabal is talking about some global constraints which is confusing for me.

Cabal dependency tree resolution gets screwed as,
    trying: parsec-3.1.8 (dependency of myproj-0.1.0.0)
next goal: mtl (dependency of parsec-3.1.8)
rejecting: mtl-2.2.1, 2.2.0.1, 2.2 (global constraint requires ==2.1.3.1)
trying: mtl-2.1.3.1
next goal: transformers (dependency of mtl-2.1.3.1)
rejecting: transformers-0.4.2.0, 0.4.1.0, 0.3.0.0, 0.2.2.1, 0.2.2.0, 0.2.1.0,
0.2.0.0, 0.1.4.0, 0.1.3.0, 0.1.1.0, 0.1.0.1, 0.1.0.0, 0.0.1.0, 0.0.0.0,
0.4.0.0 (global constraint requires installed instance)

解决方案
You should have a cabal.config file in your current directory. Open it with any text editor and serach for the transformers installed string.

Once you have found it, replace it with transformers ==0.4.3.0 or any other version you like.

                        
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