Question

在重大代码重构之后，我陷入了以下错误：

    • Couldn't match type ‘Endpoint.AuditLog.Routes
                             (AsServerT (AppM '[] ()))’
      with

      --
      -- complete API type comes here
      --

      Expected type: ServerT Routes (AppM '[] ())
        Actual type: Endpoint.AuditLog.Routes (AsServerT (AppM '[] ()))
    • In the expression: (Endpoint.AuditLog.server appRunners)
      In an equation for ‘prodServer’:
          prodServer = (Endpoint.AuditLog.server appRunners)

我已经阅读并重新阅读了the documentation，但似乎找不到错误的出处。这段代码之前已经工作了，我将Endpoint.AuditLog.server :: Routes (AsServerT AppM)更改为Endpoint.AuditLog.server :: AppRunners m n -> Routes (AsServerT n)，并确认以下表达式的类型在整个重构过程中似乎是相似的。基本上Routes (AsServerT AppM)已更改为Routes (AsServerT (AppM '[] ()))

ghci> :t (Endpoint.AuditLog.server AppM.appRunners)
(Endpoint.AuditLog.server AppM.appRunners) :: Routes (AsServerT (AppM '[] ()))

以下代码段在重构中也是结构上相同：

type Routes = (ToServant Endpoint.AuditLog.Routes AsApi)

prodServer :: ServerT Routes (AppM '[] ())
prodServer = (Endpoint.AuditLog.server AppM.appRunners)

我该如何调试此错误？由于涉及到很多类型家族，因此有什么方法可以查看以下类型级别的表达式简化为：

ServerT Routes (AppM '[] ())
Endpoint.AuditLog.Routes (AsServerT (AppM '[] ()))

Answer 1

专有！没意思！没话说！

我错过了toServant-

prodServer :: ServerT Routes (AppM '[] ())
prodServer = (toServant $ Endpoint.AuditLog.server AppM.appRunners)

如何为仆人的类型错误建立直觉？

1 个答案: