one-source-error.cabal

name:                one-source-error
version:             0.1.0.0
author:              Callum Rogers
maintainer:          some@email.com
category:            Testing
build-type:          Simple
cabal-version:       >=1.10

library
  exposed-modules:     OneSourceError
  build-depends:       base >=4.8 && <4.9
  default-language:    Haskell2010

OneSourceError.hs

module OneSourceError where

expr :: String
expr = 1 ++ "str"

Setup.hs

import Distribution.Simple
main = defaultMain

stack.yaml

packages:
  - .
resolver: lts-3.0