From 2a0a6529c817dfbfc38f8e355b40dfd94df3dfd5 Mon Sep 17 00:00:00 2001
From: Gary Burgess <gary.burgess@gmail.com>
Date: Fri, 30 Nov 2018 13:14:28 +0000
Subject: [PATCH 1/2] Reorder Inject instances to allow inj :: f ~> f

---
 src/Data/Functor/Coproduct/Inject.purs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/Data/Functor/Coproduct/Inject.purs b/src/Data/Functor/Coproduct/Inject.purs
index b16950e..8aa89d3 100644
--- a/src/Data/Functor/Coproduct/Inject.purs
+++ b/src/Data/Functor/Coproduct/Inject.purs
@@ -10,14 +10,14 @@ class Inject f g where
   inj :: forall a. f a -> g a
   prj :: forall a. g a -> Maybe (f a)
 
-instance injectLeft :: Inject f (Coproduct f g) where
+instance injectReflexive :: Inject f f where
+  inj = identity
+  prj = Just
+
+else instance injectLeft :: Inject f (Coproduct f g) where
   inj = Coproduct <<< Left
   prj = coproduct Just (const Nothing)
 
 else instance injectRight :: Inject f g => Inject f (Coproduct h g) where
   inj = Coproduct <<< Right <<< inj
   prj = coproduct (const Nothing) prj
-
-else instance injectReflexive :: Inject f f where
-  inj = identity
-  prj = Just

From 772bc6729d6405f46e7c0ee22920ea7de5bdfbbf Mon Sep 17 00:00:00 2001
From: Gary Burgess <gary.burgess@gmail.com>
Date: Fri, 30 Nov 2018 17:57:13 +0000
Subject: [PATCH 2/2] Add injection tests

---
 test/Main.purs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/test/Main.purs b/test/Main.purs
index 4ac9e34..9bf3801 100644
--- a/test/Main.purs
+++ b/test/Main.purs
@@ -2,7 +2,10 @@ module Test.Main where
 
 import Prelude
 
+import Data.Const (Const)
 import Data.Functor.Compose (Compose(..))
+import Data.Functor.Coproduct (Coproduct, left, right)
+import Data.Functor.Coproduct.Inject (inj)
 import Data.Identity (Identity(..))
 import Data.Maybe (Maybe(..))
 import Effect (Effect)
@@ -10,6 +13,11 @@ import Test.Assert (assertEqual)
 
 main :: Effect Unit
 main = do
+  testComposeOrdering
+  testInjections
+
+testComposeOrdering :: Effect Unit
+testComposeOrdering = do
   assertEqual
     { expected: Compose (Identity (Just true))
     , actual: Compose (Identity (Just true))
@@ -18,3 +26,18 @@ main = do
     { expected: Compose (Identity (Just true)) > Compose (Identity (Just false))
     , actual: true
     }
+
+testInjections :: Effect Unit
+testInjections = do
+  assertEqual
+    { expected: Identity unit
+    , actual: inj (Identity unit)
+    }
+  assertEqual
+    { expected: left (Identity unit) :: Coproduct Identity (Const Void) Unit
+    , actual: inj (Identity unit)
+    }
+  assertEqual
+    { expected: right (Identity unit) :: Coproduct (Const Void) Identity Unit
+    , actual: inj (Identity unit)
+    }