Tests don't build with GHCJS 8.4

[ElvishJerricco]

Full log: https://gist.github.com/ElvishJerricco/c3c649de21c10942b7439d0cc63dd5ff

I would not be surprised if this were a GHCJS bug. @luite, you might want to take a look.

[RyanGlScott]

I also suspect that this is a GHCJS bug, since I am unable to reproduce the issue when using the cabal flags presented in that log (excluding the Nix/GHCJS-specific ones).

[angerman]

I'm getting something very similar:

test/Main.hs:332:5: error:
    • The exact Name ‘MkT43Plain_ah7K’ is not in scope
        Probable cause: you used a unique Template Haskell name (NameU), 
        perhaps via newName, but did not bind it
        If that's it, then -ddump-splices might be useful
    • In the untyped splice:
        $(do [decPlain] <- [d| data T43Plain
                                 where MkT43Plain :: T43Plain |]
             infoPlain <- normalizeDec decPlain
             validateDI
               infoPlain
               DatatypeInfo
                 {datatypeName = mkName "T43Plain", datatypeContext = [],
                  datatypeVars = [], datatypeVariant = Datatype,
                  datatypeCons = [ConstructorInfo
                                    {constructorName = mkName "MkT43Plain", constructorVars = [],
                                     constructorContext = [], constructorFields = [],
                                     constructorStrictness = [],
                                     constructorVariant = NormalConstructor}]}
             [decFam] <- [d| data instance T43Fam where MkT43Fam :: T43Fam |]
             ....)
    |
332 |   $(do [decPlain] <- [d| data T43Plain where MkT43Plain :: T43Plain |]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...

test/Main.hs:332:5: error:
    • The exact Name ‘MkT43Plain_ah7K’ is not in scope
        Probable cause: you used a unique Template Haskell name (NameU), 
        perhaps via newName, but did not bind it
        If that's it, then -ddump-splices might be useful
    • In the untyped splice:
        $(do [decPlain] <- [d| data T43Plain
                                 where MkT43Plain :: T43Plain |]
             infoPlain <- normalizeDec decPlain
             validateDI
               infoPlain
               DatatypeInfo
                 {datatypeName = mkName "T43Plain", datatypeContext = [],
                  datatypeVars = [], datatypeVariant = Datatype,
                  datatypeCons = [ConstructorInfo
                                    {constructorName = mkName "MkT43Plain", constructorVars = [],
                                     constructorContext = [], constructorFields = [],
                                     constructorStrictness = [],
                                     constructorVariant = NormalConstructor}]}
             [decFam] <- [d| data instance T43Fam where MkT43Fam :: T43Fam |]
             ....)
    |
332 |   $(do [decPlain] <- [d| data T43Plain where MkT43Plain :: T43Plain |]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...

test/Main.hs:332:5: error:
    • The exact Name ‘MkT43Fam_ah7L’ is not in scope
        Probable cause: you used a unique Template Haskell name (NameU), 
        perhaps via newName, but did not bind it
        If that's it, then -ddump-splices might be useful
    • In the untyped splice:
        $(do [decPlain] <- [d| data T43Plain
                                 where MkT43Plain :: T43Plain |]
             infoPlain <- normalizeDec decPlain
             validateDI
               infoPlain
               DatatypeInfo
                 {datatypeName = mkName "T43Plain", datatypeContext = [],
                  datatypeVars = [], datatypeVariant = Datatype,
                  datatypeCons = [ConstructorInfo
                                    {constructorName = mkName "MkT43Plain", constructorVars = [],
                                     constructorContext = [], constructorFields = [],
                                     constructorStrictness = [],
                                     constructorVariant = NormalConstructor}]}
             [decFam] <- [d| data instance T43Fam where MkT43Fam :: T43Fam |]
             ....)
    |
332 |   $(do [decPlain] <- [d| data T43Plain where MkT43Plain :: T43Plain |]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...

test/Main.hs:332:5: error:
    • The exact Name ‘MkT43Fam_ah7L’ is not in scope
        Probable cause: you used a unique Template Haskell name (NameU), 
        perhaps via newName, but did not bind it
        If that's it, then -ddump-splices might be useful
    • In the untyped splice:
        $(do [decPlain] <- [d| data T43Plain
                                 where MkT43Plain :: T43Plain |]
             infoPlain <- normalizeDec decPlain
             validateDI
               infoPlain
               DatatypeInfo
                 {datatypeName = mkName "T43Plain", datatypeContext = [],
                  datatypeVars = [], datatypeVariant = Datatype,
                  datatypeCons = [ConstructorInfo
                                    {constructorName = mkName "MkT43Plain", constructorVars = [],
                                     constructorContext = [], constructorFields = [],
                                     constructorStrictness = [],
                                     constructorVariant = NormalConstructor}]}
             [decFam] <- [d| data instance T43Fam where MkT43Fam :: T43Fam |]
             ....)
    |
332 |   $(do [decPlain] <- [d| data T43Plain where MkT43Plain :: T43Plain |]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...
[iserv-proxy] Proxy done
builder for '/nix/store/m1kq4jy3lr0jg71c12ssrm0rla6663hf-th-abstraction-0.2.8.0-x86_64-pc-mingw32.drv' failed with exit code 1

This is not GHCJS though. This is using ghc-8.4.3 + -fexternal-interpreter. That however is pretty close to how GHCJS does TH.

@RyanGlScott you might be able to reproduce this by simply building the package with -fexternal-interpreter passed to ghc.

[RyanGlScott]

Thanks @angerman, -fexternal-interpreter was indeed sufficient to trigger this bug. I've reduced the issue to the following minimal example:

{-# LANGUAGE TemplateHaskell #-}
module Bug where

import Language.Haskell.TH

main :: IO ()
main = putStrLn $(recover (stringE "reifyFixity failed")
                          (do foo <- newName "foo"
                              _ <- reifyFixity foo
                              stringE "reifyFixity successful"))

$ /opt/ghc/8.4.3/bin/ghc Bug.hs -fforce-recomp
[1 of 1] Compiling Bug              ( Bug.hs, Bug.o )
$ /opt/ghc/8.4.3/bin/ghc Bug.hs -fforce-recomp -fexternal-interpreter
[1 of 1] Compiling Bug              ( Bug.hs, Bug.o )

Bug.hs:7:19: error:
    • The exact Name ‘foo_a3MT’ is not in scope
        Probable cause: you used a unique Template Haskell name (NameU), 
        perhaps via newName, but did not bind it
        If that's it, then -ddump-splices might be useful
    • In the untyped splice:
        $(recover
            (stringE "reifyFixity failed")
            (do foo <- newName "foo"
                _ <- reifyFixity foo
                stringE "reifyFixity successful"))
  |
7 | main = putStrLn $(recover (stringE "reifyFixity failed")
  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...

Bug.hs:7:19: error:
    • The exact Name ‘foo_a3MT’ is not in scope
        Probable cause: you used a unique Template Haskell name (NameU), 
        perhaps via newName, but did not bind it
        If that's it, then -ddump-splices might be useful
    • In the untyped splice:
        $(recover
            (stringE "reifyFixity failed")
            (do foo <- newName "foo"
                _ <- reifyFixity foo
                stringE "reifyFixity successful"))
  |
7 | main = putStrLn $(recover (stringE "reifyFixity failed")
  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...

I've opened GHC Trac #15481 for this.

[ElvishJerricco]

Should we close this issue now, seeing as this is a GHC issue, not a th-abstraction issue?

[RyanGlScott]

That sounds reasonable to me.