From fd51f6d4628c466e2871422f0cfae150f072752d Mon Sep 17 00:00:00 2001
From: Josh Leeb-du Toit <mail@joshleeb.com>
Date: Thu, 24 Mar 2022 20:32:14 +1100
Subject: [PATCH] Derive Eq on DependencyMap

This change derives the `Eq` type class on `DependencyMap` in the
`Distribution.Types` module.
---
 Cabal-syntax/src/Distribution/Types/Dependency.hs    | 4 ++++
 Cabal-syntax/src/Distribution/Types/DependencyMap.hs | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/Cabal-syntax/src/Distribution/Types/Dependency.hs b/Cabal-syntax/src/Distribution/Types/Dependency.hs
index c10910474..321ebc020 100644
--- a/Cabal-syntax/src/Distribution/Types/Dependency.hs
+++ b/Cabal-syntax/src/Distribution/Types/Dependency.hs
@@ -33,6 +33,10 @@ import qualified Text.PrettyPrint                as PP
 -- /Invariant:/ package name does not appear as 'LSubLibName' in
 -- set of library names.
 --
+-- /Note:/ 'Dependency' is not an instance of 'Ord', and so it cannot be used
+-- in 'Set' or as the key to a 'Map'.  For these and similar use cases see
+-- 'DependencyMap'.
+--
 data Dependency = Dependency
                     PackageName
                     VersionRange
diff --git a/Cabal-syntax/src/Distribution/Types/DependencyMap.hs b/Cabal-syntax/src/Distribution/Types/DependencyMap.hs
index 823857d8e..c7e66cf73 100644
--- a/Cabal-syntax/src/Distribution/Types/DependencyMap.hs
+++ b/Cabal-syntax/src/Distribution/Types/DependencyMap.hs
@@ -19,7 +19,7 @@ import qualified Data.Map.Lazy as Map
 -- | A map of dependencies.  Newtyped since the default monoid instance is not
 --   appropriate.  The monoid instance uses 'intersectVersionRanges'.
 newtype DependencyMap = DependencyMap { unDependencyMap :: Map PackageName (VersionRange, NonEmptySet LibraryName) }
-  deriving (Show, Read)
+  deriving (Show, Read, Eq)
 
 instance Monoid DependencyMap where
     mempty = DependencyMap Map.empty
-- 
2.11.4.GIT