haskell-fgl: fix build with ghc-8.6.x

pkgs/development/haskell-modules/configuration-ghc-8.6.x.nix

@@ -69,4 +69,8 @@ self: super: {
   tar = doJailbreak super.tar;                               # containers >=0.2 && <0.6
   test-framework = doJailbreak super.test-framework;         # containers >=0.1 && <0.6
 
+  # https://github.com/haskell/fgl/issues/79
+  # https://github.com/haskell/fgl/issues/81
+  fgl = appendPatch super.fgl ./patches/fgl-monad-fail.patch;
+
 }

pkgs/development/haskell-modules/patches/fgl-monad-fail.patch

@@ -0,0 +1,61 @@
+From 344a7e452630ace0f5c647e525e0299d99de5902 Mon Sep 17 00:00:00 2001
+From: Alex Washburn <github@recursion.ninja>
+Date: Mon, 20 Aug 2018 23:46:32 -0400
+Subject: [PATCH] Fixing issue with MonadFailDesugaring.
+
+---
+ .travis.yml                   |  9 +++++++++
+ Data/Graph/Inductive/Monad.hs | 14 ++++++++++++--
+ fgl.cabal                     |  3 ++-
+ 3 files changed, 23 insertions(+), 3 deletions(-)
+
+diff --git a/.travis.yml b/.travis.yml
+index db5eeb1..f026dd1 100644
+--- a/Data/Graph/Inductive/Monad.hs
++++ b/Data/Graph/Inductive/Monad.hs
+@@ -1,4 +1,4 @@
+-{-# LANGUAGE MultiParamTypeClasses #-}
++{-# LANGUAGE CPP, MultiParamTypeClasses #-}
+ 
+ -- (c) 2002 by Martin Erwig [see file COPYRIGHT]
+ -- | Monadic Graphs
+@@ -19,6 +19,10 @@ module Data.Graph.Inductive.Monad(
+ 
+ 
+ import Data.Graph.Inductive.Graph
++#if MIN_VERSION_base(4,12,0)
++import Control.Monad.Fail
++import Prelude hiding (fail)
++#endif
+ 
+ {-# ANN module "HLint: ignore Redundant lambda" #-}
+ 
+@@ -39,7 +43,13 @@ import Data.Graph.Inductive.Graph
+ 
+ -- Monadic Graph
+ --
+-class (Monad m) => GraphM m gr where
++class
++#if MIN_VERSION_base(4,12,0)
++ (MonadFail m)
++#else
++ (Monad m)
++#endif
++  => GraphM m gr where
+   {-# MINIMAL emptyM, isEmptyM, matchM, mkGraphM, labNodesM #-}
+ 
+   emptyM     :: m (gr a b)
+diff --git a/fgl.cabal b/fgl.cabal
+index 4251a21..4b2a039 100644
+--- a/fgl.cabal
++++ b/fgl.cabal
+@@ -18,7 +18,8 @@ extra-source-files:
+                ChangeLog
+ 
+ tested-with:   GHC == 7.0.4, GHC == 7.2.2, GHC == 7.4.2, GHC == 7.6.3,
+-               GHC == 7.8.4, GHC == 7.10.2, GHC == 8.0.1, GHC == 8.1.*
++               GHC == 7.8.4, GHC == 7.10.2, GHC == 8.0.1, GHC == 8.2.2,
++               GHC == 8.4.3, GHC == 8.6.1
+ 
+ source-repository head
+     type:         git