Problem with Template Haskell and deriving Data for newtypes #976
Description
ghcide fails to compile modules that use TemplateHaskell and also derive Data for newtypes. Using a template Haskell expression from such a module in another module fails, even if the newtype isn't exported.
File src/A.hs:
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE TemplateHaskell #-}
module A (a) where
import Data.Data
import Language.Haskell.TH
newtype A = A () deriving (Data)
-- if the deriving clause is removed the issue goes away
a :: ExpQ
a = [| 0 |]File src/B.hs:
{-# LANGUAGE TemplateHaskell #-}
module B where
import A
b :: Int
b = $( a )File: hie.yaml
cradle:
direct:
arguments:
- '-isrc'
The error message in file src/B.hs is:
[typecheck] [E] Program error:
ByteCodeLink.lookupCE
During interactive linking, GHCi couldn't find the following symbol:
A_A_closure
This may be due to you not asking GHCi to load extra object files,
archives or DLLs needed by your current session. Restart GHCi, specifying
the missing library using the -L/path/to/object/dir and -lmissinglibname
flags, or simply by naming the relevant files on the GHCi command line.
Alternatively, this link failure might indicate a bug in GHCi.
If you suspect the latter, please send a bug report to:
glasgow-haskell-bugs@haskell.org
Running ghcide gives:
lars@paul:~/Code/github/ghcide/tmp (master) [GHC-8.8.1]$ ghcide
ghcide version: 0.0.6 (GHC: 8.8.1) (PATH: /Users/lars/.cabal/bin/ghcide) (GIT hash: 913aa5f9fa3508dcbe423aea3e0d0effe1b57d1b)
Ghcide setup tester in /Users/lars/Code/github/ghcide/tmp.
Report bugs at https://github.com/digital-asset/ghcide/issues
Step 1/6: Finding files to test in /Users/lars/Code/github/ghcide/tmp
Found 2 files
Step 2/6: Looking for hie.yaml files that control setup
Found 1 cradle
Step 3/6, Cradle 1/1: Loading ./hie.yaml
Step 4/6, Cradle 1/1: Loading GHC Session
Loaded package environment from /Users/lars/.ghc/x86_64-darwin-8.8.1/environments/default
Step 5/6: Initializing the IDE
Step 6/6: Type checking the files
ghcide: ^^ Could not load '_A_A_closure', dependency unresolved. See top entry above.
Files that failed:
* ./src/B.hs
Completed (1 file worked, 1 file failed)
File: src/B.hs
Hidden: no
Range: 1:0-100001:0
Source: typecheck
Severity: DsError