esqueleto: fix compilation with ghc-8.0.1

[vandenoever]

Motivation for this change

#19247

patch from here: prowdsponsor/esqueleto#150

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • OS X
  • Linux
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

---

[mention-bot]

@vandenoever, thanks for your PR! By analyzing the history of the files in this pull request, we identified @peti, @acowley and @bennofs to be potential reviewers.

[peti]

This patch pins our version of esqueleto unconditionally to an more or less arbitrary git commit plus patches that upstream has not approved in any way. This kind of override is a maintenance nightmare because it will silently break updates in the main hackage-packages.nix file.

[peti]

Dude, if you want to help improve the current situation, please help fix esqueleto UPSTREAM, i.e. on Hackage. Nixpkgs is not the right place to make these kind of intrusive changes. I find it somewhat annoying that it feels like I'm repeating the same point over and over again without achieving any observable affect.

[vandenoever]

The same type of fix is present for structured-haskell-mode.
I do not want to take over maintainership of esqueleto.

[peti]

The same type of fix is present for structured-haskell-mode.

We don't have any alternative there because structured-haskell-mode is outright broken with Emacs 25.x, which is the only version we have, so we need a git snapshot to have anything that's usable. esqueleto, on the other hand, compiles and works just fine with appropriate versions of persistent, which we do have in Nixpkgs.