windows – 编译qtHaskell时发生错误

在qmake和mingw32-make之后,these指令成功,
并且我执行runhaskell Setup.hs build,我收到以下错误：

[651 of 662] Compiling Qtc.Core.Attributes ( Qtc\Core\Attributes.hs,dist\build\Qtc\Core\Attributes.o )
Qtc\Core\Attributes.hs:584:13:
Could not deduce (Qstt a (QDialogSc b))
  arising from a use of `slotReject''
from the context (Qstt a (QDialogSc b1))
  bound by the instance declaration
  at Qtc\Core\Attributes.hs:582:10-52
Possible fix:
  add (Qstt a (QDialogSc b)) to the context of
    the instance declaration
  or add an instance declaration for (Qstt a (QDialogSc b))
In the expression: slotReject'
In an equation for `reject'': reject' = slotReject'
In the instance declaration for `QsaSlotReject a'

Attributes.hs文件(第578 – 583行)：

class QsaSlotReject w where
  slotReject',reject' ::  (Qslot w (w -> ()),(w -> ()))

instance (Qstt a (QDialogSc b)) => QsaSlotReject (a) where
  slotReject' = (Qslot "reject()",\_ -> ())
  reject' = slotReject'

环境 ：

> Windows 7
> Haskell平台2011.2.0
> Qt sdk 4.7

顺便说一句,我在这个过程中遇到了两次内存不足,但我猜这没关系.

麻烦来自于这个事实

data Qslot x f = Qslot String

因此,从Qslot“Blah blah”形式的给定项目推断x和f可能有点困难.自从去年秋天qthaskell的最后一个版本上升以来,GHC使用的推理机制可能发生了微妙的变化.

在任何情况下,它似乎编译,带有一些好奇的警告,并且示例工作,如果你替换

instance (Qstt a (QDialogSc b)) => QsaSlotReject (a) where
    slotReject' = (Qslot "reject()",\_ -> ())
    reject' = slotReject'

同

instance (Qstt a (QDialogSc b)) => QsaSlotReject (a) where
   slotReject' = (Qslot "reject()",\_ -> ())
   reject' = (Qslot "reject()",\_ -> ())

那样ghc就不用多想了……

必须有一些东西可以使事情更精确.我不知道eta减少警告是否会在以后系统地开始出现,这与此线路有关.

原文地址：https://www.jb51.cc/windows/365236.html