Trouble installing ghc-mod

Question

I'm trying to install GHC-MOD on Windows 10 x64 on GHC 8.0.1 with cabal:

C:\WINDOWS\system32>cabal install ghc-mod
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: ghc-mod-5.5.0.0 (user goal)
trying: djinn-lib-0.0.1.2/installed-I8G... (dependency of djinn-ghc-0.0.2.3)
next goal: mtl (dependency of ghc-mod-5.5.0.0)
rejecting: mtl-2.2.1/installed-6qs... (conflict: mtl =>
transformers==0.5.2.0/installed-0.5..., ghc-mod => transformers<0.5)
rejecting: mtl-2.2.1, mtl-2.2.0.1, mtl-2.2, mtl-2.1.3.1, mtl-2.1.2, mtl-2.1.1,
mtl-2.1, mtl-2.0.1.1, mtl-2.0.1.0, mtl-2.0.0.0, mtl-1.1.1.1, mtl-1.1.1.0,
mtl-1.1.0.2, mtl-1.1.0.1, mtl-1.1.0.0, mtl-1.0 (conflict: djinn-lib =>
mtl==2.2.1/installed-6qs...)
Backjump limit reached (currently 2000, change with --max-backjumps or try to
run with --reorder-goals).

Then changing backjumps:

C:\WINDOWS\system32>cabal install ghc-mod --max-backjumps 9999
Resolving dependencies...
Configuring old-time-1.1.0.3...
Failed to install old-time-1.1.0.3
Build log ( C:\Users\xx\AppData\Roaming\cabal\logs\old-time-1.1.0.3.log ):
Configuring old-time-1.1.0.3...
configure: WARNING: unrecognized options: --with-compiler
checking for gcc... C:\PROGRA~1\HASKEL~1\802E01~1.1\mingw\bin\gcc.exe
checking whether the C compiler works... no
configure: error: in `/cygdrive/c/Users/xx/AppData/Local/Temp/cabal-tmp-3644/old-time-1.1.0.3':
configure: error: C compiler cannot create executables
See `config.log' for more details
cabal: Leaving directory 'C:\Users\xx\AppData\Local\Temp\cabal-tmp-3644\old-time-1.1.0.3'
cabal: Error: some packages failed to install:
cpphs-1.20.1 depends on old-time-1.1.0.3 which failed to install.
ghc-mod-5.0.0 depends on old-time-1.1.0.3 which failed to install.
haskell-src-exts-1.17.1 depends on old-time-1.1.0.3 which failed to install.
hlint-1.9.32 depends on old-time-1.1.0.3 which failed to install.
old-time-1.1.0.3 failed during the configure step. The exception was:
ExitFailure 77

I've tried installing both MinGW+MSYS and Cygwin, but neither works. All the GHC folders are in the PATH environment variable.

Answer 1

https://github.com/DanielG/ghc-mod/issues/798

Officially, ghc-mod is not updated to GHC 8. There's a branch ghc-8 for it where some tests are still broken but other things supposedly work.

The ghc-8 branch seems to work for me. It builds and I can use it. I use Stack on Linux.