fix(xanthous): Fix display of square/cubic units r/2684

Previously this'd display `5 m m³`, because it'd show the underlying
value then add the unit suffix on at the end

Change-Id: Idd240ddfebc212460f9fb529eff72732a5dafe2a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3241
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

2 files changed, 11 insertions, 4 deletions

diff --git a/users/grfn/xanthous/src/Xanthous/Data.hs b/users/grfn/xanthous/src/Xanthous/Data.hs
index 77b0f8f8be..9b3c35c545 100644
--- a/users/grfn/xanthous/src/Xanthous/Data.hs
+++ b/users/grfn/xanthous/src/Xanthous/Data.hs
@@ -557,7 +557,6 @@ newtype Square a = Square a
            , Scalar
            )
        via a
-  deriving Show via ShowUnitSuffix (Square a) a
 deriving via (a :: Type)
   instance ( Distribution d a
            , forall xx yy. Coercible xx yy => Coercible (d xx) (d yy)
@@ -567,6 +566,9 @@ deriving via (a :: Type)
 instance Unit a => Unit (Square a) where
   unitSuffix = unitSuffix @a <> "²"
 
+instance Show a => Show (Square a) where
+  show (Square n) = show n <> "²"
+
 newtype Cubic a = Cubic a
   deriving stock (Eq, Generic)
   deriving anyclass (NFData, CoArbitrary, Function)
@@ -574,7 +576,6 @@ newtype Cubic a = Cubic a
            , Scalar
            )
        via a
-  deriving Show via ShowUnitSuffix (Cubic a) a
 deriving via (a :: Type)
   instance ( Distribution d a
            , forall xx yy. Coercible xx yy => Coercible (d xx) (d yy)
@@ -584,6 +585,9 @@ deriving via (a :: Type)
 instance Unit a => Unit (Cubic a) where
   unitSuffix = unitSuffix @a <> "³"
 
+instance Show a => Show (Cubic a) where
+  show (Cubic n) = show n <> "³"
+
 
 --------------------------------------------------------------------------------
 
diff --git a/users/grfn/xanthous/test/Xanthous/DataSpec.hs b/users/grfn/xanthous/test/Xanthous/DataSpec.hs
index 1aa250b1a4..9e67505ba9 100644
--- a/users/grfn/xanthous/test/Xanthous/DataSpec.hs
+++ b/users/grfn/xanthous/test/Xanthous/DataSpec.hs
@@ -99,8 +99,11 @@ test = testGroup "Xanthous.Data"
   , testGroup "units"
     [ testGroup "unit suffixes"
       [ testCase "density"
-        $ tshow (10000 :: Grams `Per` Cubic Meters)
-          @?= "10000.0 g/m³"
+        $ tshow (10000 :: Grams `Per` Cubic Meters) @?= "10000.0 g/m³"
+      , testCase "volume"
+        $ tshow (5 :: Cubic Meters) @?= "5.0 m³"
+      , testCase "area"
+        $ tshow (5 :: Square Meters) @?= "5.0 m²"
       ]
     ]
   ]