OverloadedStrings causes type-defaults warning

[wataru86]

I tried using optparse-simple in my repository.
I added OverloadedStrings pragma to Sample.hs.

{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE OverloadedStrings #-}
module Main (main) where

import           Options.Applicative.Simple (simpleVersion)
import qualified Paths_SampleA as Meta

main :: IO ()
main = putStrLn $(simpleVersion Meta.version)

First, I tried using github version. (SampleA)
I wrote stack.yaml as below.

resolver: lts-13.1
packages:
- .
extra-deps:
- github: fpco/optparse-simple
  commit: 2e816d643e813a32057242c6992ff7ce9c9eceb1

There was no warning.

Next, I tried using hackage version. (SampleB)
I wrote stack.yaml as below.

resolver: lts-13.1
packages:
- .

I got the following type-defaults warning.

$ stack build
Building all executables for `SampleB' once. After a successful build of all of them, only specified executables will be rebuilt.
SampleB-0.1.0.0: configure (exe)
Configuring SampleB-0.1.0.0...
SampleB-0.1.0.0: build (exe)
Preprocessing executable 'SampleB-exe' for SampleB-0.1.0.0..
Building executable 'SampleB-exe' for SampleB-0.1.0.0..
[1 of 2] Compiling Paths_SampleB    ( .stack-work/dist/x86_64-linux/Cabal-2.4.0.1/build/SampleB-exe/autogen/Paths_SampleB.hs, .stack-work/dist/x86_64-linux/Cabal-2.4.0.1/build/SampleB-exe/SampleB-exe-tmp/Paths_SampleB.o )
[2 of 2] Compiling Main             ( app/Main.hs, .stack-work/dist/x86_64-linux/Cabal-2.4.0.1/build/SampleB-exe/SampleB-exe-tmp/Main.o )

/home/yamada/test/190106/sample-optparse-simple/SampleB/app/Main.hs:9:19: warning: [-Wtype-defaults]
    • Defaulting the following constraint to type ‘[Char]’
        Data.String.IsString a0
          arising from the literal ‘"GHEGitRunFailed "." ["rev-parse","--show-toplevel"] (ExitFailure 128) "" "fatal: Not a git repository (or any of the parent directories): .git\n""’
    • In the first argument of ‘Left’, namely
        ‘"GHEGitRunFailed "." ["rev-parse","--show-toplevel"] (ExitFailure 128) "" "fatal: Not a git repository (or any of the parent directories): .git\n""’
      In the expression:
        Left
          "GHEGitRunFailed "." ["rev-parse","--show-toplevel"] (ExitFailure 128) "" "fatal: Not a git repository (or any of the parent directories): .git\n""
      In the second argument of ‘(++)’, namely
        ‘(case
              Left
                "GHEGitRunFailed "." ["rev-parse","--show-toplevel"] (ExitFailure 128) "" "fatal: Not a git repository (or any of the parent directories): .git\n""
          of
            Left _ -> []
            Right gi_a6X0
              -> [", Git revision ", githash-0.1.3.0:GitHash.giHash gi_a6X0,
                  if githash-0.1.3.0:GitHash.giDirty gi_a6X0 then
                      " (dirty)"
                  else
                      ""])’
  |
9 | main = putStrLn $(simpleVersion Meta.version)
  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
Linking .stack-work/dist/x86_64-linux/Cabal-2.4.0.1/build/SampleB-exe/SampleB-exe ...

SampleB-0.1.0.0: copy/register
Installing executable SampleB-exe in /home/yamada/test/190106/sample-optparse-simple/SampleB/.stack-work/install/x86_64-linux/lts-13.1/8.6.3/bin

GitHub version is almost the same as hackage version.
Why does hackage version got warning?

stack version is 1.9.3.

[snoyberg]

This one is a head scratcher. I can't explain why Hackage vs Git causes this difference. However, I can trace the problem back to a missing type signature in githash (addressed with snoyberg/githash@f0d48dd). I'll make a new release once CI passes, and then future LTSes should work just fine. Thanks for the report!