Can't build from source with 8.10.7: ‘coreExprToBCOs’ is applied to too few arguments

[maksbotan]

Your environment

Which OS do you use:
macOS 11.6.2
Which LSP client (editor/plugin) do you use:
neovim + coc-nvim
Describe your project (alternative: link to the project):
Not relevant

Steps to reproduce

Basically, I did

1. Git clone the repo
2. git checkout 1.7.0.0
3. cabal new-build exe:haskell-language-server

I have cabal and ghc 8.10.7 in my $PATH, installed from haskell.nix.

$ cabal --version
cabal-install version 3.6.2.0
compiled using version 3.6.2.0 of the Cabal library 
$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 8.10.7

Expected behaviour

I expect cabal to build me a haskell-language-server exe.

Actual behaviour

Building of ghcide package breaks with this error:

src/Development/IDE/Core/Compile.hs:260:22: error:
    • Couldn't match expected type ‘IO ByteCodeTypes.UnlinkedBCO’
                  with actual type ‘StgSyn.StgRhs -> IO ByteCodeTypes.UnlinkedBCO’
    • Probable cause: ‘coreExprToBCOs’ is applied to too few arguments
      In a stmt of a 'do' block:
        bcos <- coreExprToBCOs
                  hsc_env (icInteractiveModule (hsc_IC hsc_env)) prepd_expr
      In the expression:
        do let dflags = hsc_dflags hsc_env
           simpl_expr <- simplifyExpr dflags hsc_env ds_expr
           let tidy_expr = tidyExpr emptyTidyEnv simpl_expr
           prepd_expr <- corePrepExpr dflags hsc_env tidy_expr
           ....
      In an equation for ‘compile_bco_hook’:
          compile_bco_hook var hsc_env srcspan ds_expr
            = do let dflags = ...
                 simpl_expr <- simplifyExpr dflags hsc_env ds_expr
                 let tidy_expr = ...
                 ....
    |
260 |            ; bcos <- coreExprToBCOs hsc_env
    |                      ^^^^^^^^^^^^^^^^^^^^^^...

src/Development/IDE/Core/Compile.hs:261:63: error:
    • Couldn't match type ‘CoreSyn.Expr CoreSyn.CoreBndr’
                     with ‘GHC.Var’
      Expected type: Id
        Actual type: CoreExpr
    • In the third argument of ‘coreExprToBCOs’, namely ‘prepd_expr’
      In a stmt of a 'do' block:
        bcos <- coreExprToBCOs
                  hsc_env (icInteractiveModule (hsc_IC hsc_env)) prepd_expr
      In the expression:
        do let dflags = hsc_dflags hsc_env
           simpl_expr <- simplifyExpr dflags hsc_env ds_expr
           let tidy_expr = tidyExpr emptyTidyEnv simpl_expr
           prepd_expr <- corePrepExpr dflags hsc_env tidy_expr
           ....
    |
261 |                        (icInteractiveModule (hsc_IC hsc_env)) prepd_expr
    |                                                               ^^^^^^^^^^

Include debug information

I attach cabal.project.freeze generated by cabal new-freeze just in case.

cabal.project.freeze.txt

[wz1000]

How did you install GHC? In GHC 8.10.7, coreExprToBCOs has type HscEnv -> Module -> CoreExpr -> IO UnlinkedBCO

Can you start a GHCi session with -package ghc, import ByteCodeGen and then ask for :type coreExprToBCOs?

[amesgen]

Also hitting this issue with haskell.nix, and indeed, the type is different:

 Λ :t coreExprToBCOs
coreExprToBCOs
  :: HscTypes.HscEnv
     -> Module.Module -> Var.Id -> StgSyn.StgRhs -> IO UnlinkedBCO

So this seems like a haskell.nix issue as it uses slightly patched GHCs. I opened input-output-hk/haskell.nix#1455 to track this.

[wz1000]

It seems like the culprit is haskell.nix: https://github.com/input-output-hk/haskell.nix/blob/a5b74bf002bee3ee41012c8f5e48105150892eee/overlays/patches/ghc/ghc-8.10.5-ubxt.patch

This is a downstream issue since we can't conceivably support all custom distributions of GHC.

[maksbotan]

@wz1000

Turns out haskell.nix applies a patch to 8.10 series:
https://github.com/input-output-hk/haskell.nix/blob/master/overlays/patches/ghc/ghc-8.10.5-ubxt.patch

Among other things it has this:

@@ -155,23 +167,25 @@ literals:
 -- Returns: the root BCO for this expression
 coreExprToBCOs :: HscEnv
                -> Module
-               -> CoreExpr
+               -> Id
+               -> StgRhs
                -> IO UnlinkedBCO
-coreExprToBCOs hsc_env this_mod expr
+coreExprToBCOs hsc_env this_mod bndr expr

Do you maybe know corresponding upstream MR? I could not find any reference in haskell.nix repository :/

$ ghci -package ghc
GHCi, version 8.10.7: https://www.haskell.org/ghc/  :? for help
Loaded package environment from /Users/maksbotan/.ghc/x86_64-darwin-8.10.7/environments/default
Loaded GHCi configuration from /Users/maksbotan/.ghci
λ> import ByteCodeGen
λ> :type coreExprToBCOs
coreExprToBCOs
  :: HscTypes.HscEnv
     -> Module.Module -> Var.Id -> StgSyn.StgRhs -> IO UnlinkedBCO

[maksbotan]

@amesgen thanks for reporting this to haskell.nix!

[maksbotan]

For anyone interested, I was able to patch HLS source to compile with haskell.nix's compiler. Going to test this setup.

https://gist.github.com/maksbotan/8c7a8f531163c58da9983fbc48d45fff

[amesgen]

The patch by @maksbotan is now part of haskell.nix, see input-output-hk/haskell.nix#1457

[wz1000]

Closing as this is a downstream packaging issue.