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reproduceAeson

Upgrade error to resolver:19.33 from resolver:18.28

What works ?

in stack.yaml ,resolver: lts-18.28

in the stack

*Lib> encode $ AppleA
"{\"tag\":\"AppleA\"}"

What fails ?

in stack.yaml ,resolver: lts-19.33

then the stack will failed to compile ..

(for Mac M chips)

When stack compiling need t include extra flag

export C_INCLUDE_PATH="`xcrun --show-sdk-path`/usr/include/ffi"; stack build

Conclusion

It seems that Template Haskell make a stricter changes since solver-lts-19.33. The circular reference is not allowed.

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Debug Log

Package diff

https://www.stackage.org/diff/lts-18.28/lts-19.33

resolver: lts-18.28
extra-deps:

aeson-2.0.3.0

Success

resolver: lts-19.33
extra-deps:

aeson-1.5.6.0

Failed

error message in lts 19.33

Error when using LTS-19.33

Step

pull the code from repo
change the lts to 19.33
run stack build

Debug with play.haskell.org

https://play.haskell.org/

below code works with GHC-8.10.7 but failed with GHC 9.0.2

`
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE InstanceSigs #-}

import Control.Monad (replicateM)
import Data.Foldable (foldl')
import qualified System.Random.Stateful as Rand

import GHC.Generics
import Data.Aeson hiding (json)
import Data.Aeson.TH
import Data.Aeson.Types


data Size = Big   
          | Small Apple
            deriving (Show,Eq,Ord,Read,Generic)


data Apple = AppleA
           | AppleB  Size
           | Apples Apple
            deriving (Show,Eq,Ord,Read,Generic)


$(deriveJSON defaultOptions ''Size)
$(deriveJSON defaultOptions ''Apple)

main :: IO ()
main = do

  print "HELLO"

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