how to use a specific branch of llvm-general with stack - haskell

Question

In one of my projects I want to use llvm-general and llvm-general-pure but I want to use the llvm-3.9 branch which works with llvm 3.9, the latest version of these libraries on hackage are for llvm 3.5.
My project is a stack project, this is what I have in stack.yaml :
resolver: nightly-2017-05-01
packages:
- '.'
- location:
git: https://github.com/bscarlet/llvm-general.git
commit: 61fd03639063283e7dc617698265cc883baf0eec
subdirs:
- llvm-general
- llvm-general-pure
extra-dep: true
All other options are left to default.
This is my project.cabal :
name: compiler-final
version: 0.1.0.0
category: Compiler
build-type: Simple
-- extra-source-files:
cabal-version: >=1.10
library
hs-source-dirs: src
exposed-modules: Lexer,Parser,ParserTestData,CodeGen
other-modules: Prelude,StateTUtil
ghc-options: -Wall -dcore-lint -fhpc -XNoImplicitPrelude -fobject-code
build-depends: base-noprelude >= 4.7 && < 5 , megaparsec < 6 , transformers < 1, unordered-containers < 1 , hashable < 2
,classy-prelude , either < 5 , mono-traversable < 2 , logfloat < 0.14 , text
default-language: Haskell2010
default-extensions: OverloadedStrings
executable compiler-final-exe
hs-source-dirs: app
main-is: Main.hs
ghc-options: -threaded -rtsopts -XNoImplicitPrelude -with-rtsopts=-N -fobject-code
build-depends: base
, compiler-final
default-language: Haskell2010
default-extensions: OverloadedStrings
test-suite compiler-final-test
type: exitcode-stdio-1.0
hs-source-dirs: test
other-modules: LexerSpec , ParserSpec
main-is: Spec.hs
build-depends: base
, compiler-final, megaparsec < 6 , hspec < 3,hspec-megaparsec >= 0.3,unordered-containers < 1
,hashable,transformers < 1,text,bytestring , mtl, text
ghc-options: -threaded -rtsopts -with-rtsopts=-N -fhpc -Wall -XNoImplicitPrelude -fobject-code
default-language: Haskell2010
default-extensions: OverloadedStrings
Benchmark compiler-final-bench
type: exitcode-stdio-1.0
hs-source-dirs: bench
main-is: Bench.hs
other-modules: ParserBench
build-depends: base,compiler-final,megaparsec < 6 ,unordered-containers < 1,QuickCheck<3
,hashable
ghc-options: -rtsopts -auto-all -caf-all -fforce-recomp -fobject-code
default-language: Haskell2010
Unfortunately in CodeGen.hs this simple import statement doesn't compile : import LLVM.General.AST, it says it didn't find the module.
Now I have llvm-general branch 3.9 installed globally through cabal install and I can access it with ghci -package(not stack ghci) and the above module exists.
I tried adding llvm-general and llvm-general-pure to my dependencies list with version 3.9.0.0 but stack seems to try to install version 3.5 because it reports errors about mismatched versions.
So how to achieve what I want ?

Answer 1

Your .cabal does not list llvm-general and llvm-general-pure as dependencies, hence why LLVM.General.AST is not being found.
Moreover, your stack.yaml is pointing to master, so stack will only see version 3.5. stack doesn't know anything about version 3.9 if it's not in the stack.yaml file. Either:
change the commit to ec1ad5bd2112e7f64dbb43441b5e2075cf6ad8e;
or, if you have the branch cloned locally, you can replace the whole location field corresponding to the repository with
- location: 'path/to/llvm-general'
extra-dep: true
- location: 'path/to/llvm-general-pure'
extra-dep: true