From c7d396732bd45e409478bd4df1d0ca95d6f39356 Mon Sep 17 00:00:00 2001
From: Herbert Valerio Riedel <hvr@gnu.org>
Date: Sat, 24 Feb 2018 22:48:36 +0100
Subject: [PATCH] Explicitly declare the API contract of `mtl` to be "safe"

This avoids relying on the fragile "safe-inferred" status
and thus gives `mtl` a more explicit SafeHaskell API contract.

C.f. https://github.com/haskell/pvp/issues/22
---
 mtl.cabal | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mtl.cabal b/mtl.cabal
index 2670a81..7f11397 100644
--- a/mtl.cabal
+++ b/mtl.cabal
@@ -66,6 +66,11 @@ Library
     FlexibleInstances
     UndecidableInstances
 
+  -- This is a SafeHaskell safeguard (pun intended) to explicitly declare the API contract of `mtl`
+  -- GHC versions before 7.4 were hopelessly broken or incapable of SafeHaskell
+  if impl(ghc >= 7.4)
+    default-extensions: Safe
+
   ghc-options: -Wall -fno-warn-unused-imports -fno-warn-warnings-deprecations
 
   if impl(ghc >= 8.0)