启用了 mpsGeneric 的 Key 的 Eq 实例看起来很奇怪

Question

{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE QuasiQuotes #-}
module Main
  where

import           Database.Persist.Sql
import           Database.Persist.TH

share
    [mkPersist
        sqlSettings
            { mpsGeneric = True
            , mpsPrefixFields = False
            , mpsEntityJSON = Just EntityJSON
                                { entityToJSON = 'keyValueEntityToJSON
                                , entityFromJSON = 'keyValueEntityFromJSON
                                }
            , mpsGenerateLenses = False
            }
    , mkMigrate "abc"]
    [persistLowerCase|
Test
    a String
|]

main :: IO ()
main = do
    print $ (toSqlKey 1 :: TestId) /= (toSqlKey 1 :: TestId)
    print $ (toSqlKey 1 :: TestId) == (toSqlKey 1 :: TestId)

    print $ (toSqlKey 1 :: TestId) /= (toSqlKey 2 :: TestId)
    print $ (toSqlKey 1 :: TestId) == (toSqlKey 2 :: TestId)

在这个haskell程序中，我启用了mpsGeneric开关，这个程序的结果是：

True
True
False
False

如果禁用mpsGeneric，结果是：

True
False
False
True

看来，上面那个Eq实例坏了。我用

测试程序

persistent of version 2.2.4.1
persistent-template of version 2.1.6

这个 "feature" 让我整个下午都死了 ，当我运行以下代码时：

filter (/= someKey) [key1, key2, key3]

Answer 1

这是一个错误。现在 github 报道：https://github.com/yesodweb/persistent/issues/560

启用了 mpsGeneric 的 Key 的 Eq 实例看起来很奇怪

The Eq instance of a Key with mpsGeneric enabled seems strange

haskell

persistent

yesod