Haskell DeriveGeneric pragma 未被识别

Question

我的 Haskell 文件顶部有以下内容：

{-# LANGUAGE DeriveGeneric,  OverloadedStrings,  DefaultSignatures,  TypeOperators,  FlexibleContexts, RecordWildCards, FlexibleInstances, ExtendedDefaultRules #-}

module Main where

import qualified Data.Map as Map
import qualified Data.Set as Set
import Data.Text (Text)
import Data.DateTime
import Data.Aeson

newtype Price = Price Float deriving Generic

然而，当我运行:

$ stack ghci
...
Prelude> :l myfile.hs

[1 of 1] Compiling Main             ( myfile.hs, interpreted )

myfile.hs:13:38: error:
    Not in scope: type constructor or class ‘Generic’
   |
13 | newtype Price = Price Float deriving Generic
   |                                      ^^^^^^^
Failed, no modules loaded.

它似乎不接受我对泛型的 pragma。我究竟做错了什么？查看，这似乎应该可行。

Answer 1

您还需要导入 GHC.Generics:

-- other imports
import GHC.Generics
-- more imports

Haskell DeriveGeneric pragma 未被识别

Haskell DeriveGeneric pragma not being recognized

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