Add missing Semigroup instances to compiler

This is a pre-requisite for implementing the Semigroup/Monoid proposal.
The instances have been introduced in a way to minimise warnings.

1 files changed, 13 insertions, 16 deletions

diff --git a/compiler/main/Packages.hs b/compiler/main/Packages.hs
index 01d66cb740..088f58a675 100644
--- a/compiler/main/Packages.hs
+++ b/compiler/main/Packages.hs
@@ -217,14 +217,7 @@ instance Semigroup ModuleOrigin where
 
 instance Monoid ModuleOrigin where
     mempty = ModOrigin Nothing [] [] False
-    mappend (ModOrigin e res rhs f) (ModOrigin e' res' rhs' f') =
-        ModOrigin (g e e') (res ++ res') (rhs ++ rhs') (f || f')
-      where g (Just b) (Just b')
-                | b == b'   = Just b
-                | otherwise = panic "ModOrigin: package both exposed/hidden"
-            g Nothing x = x
-            g x Nothing = x
-    mappend _ _ = panic "ModOrigin: hidden module redefined"
+    mappend = (Semigroup.<>)
 
 -- | Is the name from the import actually visible? (i.e. does it cause
 -- ambiguity, or is it only relevant when we're making suggestions?)
@@ -283,6 +276,17 @@ instance Outputable UnitVisibility where
         uv_requirements = reqs,
         uv_explicit = explicit
     }) = ppr (b, rns, mb_pn, reqs, explicit)
+
+instance Semigroup UnitVisibility where
+    uv1 <> uv2
+        = UnitVisibility
+          { uv_expose_all = uv_expose_all uv1 || uv_expose_all uv2
+          , uv_renamings = uv_renamings uv1 ++ uv_renamings uv2
+          , uv_package_name = mappend (uv_package_name uv1) (uv_package_name uv2)
+          , uv_requirements = Map.unionWith Set.union (uv_requirements uv1) (uv_requirements uv2)
+          , uv_explicit = uv_explicit uv1 || uv_explicit uv2
+          }
+
 instance Monoid UnitVisibility where
     mempty = UnitVisibility
              { uv_expose_all = False
@@ -291,14 +295,7 @@ instance Monoid UnitVisibility where
              , uv_requirements = Map.empty
              , uv_explicit = False
              }
-    mappend uv1 uv2
-        = UnitVisibility
-          { uv_expose_all = uv_expose_all uv1 || uv_expose_all uv2
-          , uv_renamings = uv_renamings uv1 ++ uv_renamings uv2
-          , uv_package_name = mappend (uv_package_name uv1) (uv_package_name uv2)
-          , uv_requirements = Map.unionWith Set.union (uv_requirements uv1) (uv_requirements uv2)
-          , uv_explicit = uv_explicit uv1 || uv_explicit uv2
-          }
+    mappend = (Semigroup.<>)
 
 type WiredUnitId = DefUnitId
 type PreloadUnitId = InstalledUnitId