From 505168f78302de45c8f2c3a263ed5fc44f38f8a5 Mon Sep 17 00:00:00 2001
From: Sridhar Ratnakumar <srid@srid.ca>
Date: Sat, 2 Jul 2022 14:11:41 -0400
Subject: [PATCH] subRoutesIso doesn't havae to be a class method

---
 src/Ema/Route/Generic.hs          |  9 ++-------
 src/Ema/Route/Generic/SubRoute.hs | 29 +++++++++++------------------
 2 files changed, 13 insertions(+), 25 deletions(-)

diff --git a/src/Ema/Route/Generic.hs b/src/Ema/Route/Generic.hs
index b5d2205..7374b47 100644
--- a/src/Ema/Route/Generic.hs
+++ b/src/Ema/Route/Generic.hs
@@ -32,7 +32,7 @@ import Ema.Route.Lib.Folder (FolderRoute (FolderRoute))
 import Ema.Route.Lib.Multi (MultiModel, MultiRoute)
 import GHC.Generics qualified as GHC
 import Generics.SOP (All, I (..), NP)
-import Optics.Core (ReversibleOptic (re), equality, review)
+import Optics.Core (ReversibleOptic (re), coercedTo, equality, review, (%))
 import Prelude hiding (All, Generic)
 
 -- | DerivingVia type to generically derive `IsRoute`
@@ -125,10 +125,6 @@ instance
   HasSubRoutes (GenericRoute r opts)
   where
   type SubRoutes (GenericRoute r opts) = OptSubRoutes r opts
-  subRoutesIso' =
-    (,)
-      (gtoSubRoutes @r @(OptSubRoutes r opts) . rfrom . coerce @_ @r)
-      (coerce @r . rto . gfromSubRoutes @r)
 
 instance
   ( GSubModels (RouteModel (GenericRoute r opts)) (MultiModel (OptSubRoutes r opts)) (OptSubModels r opts)
@@ -152,7 +148,6 @@ instance
   , mm ~ MultiModel (SubRoutes r)
   , a ~ RouteModel r
   , a ~ OptModel r opts
-  , SubRoutes r ~ OptSubRoutes r opts
   , IsRoute mr
   , RouteModel mr ~ NP I mm
   , GenericRouteOpts r opts
@@ -162,7 +157,7 @@ instance
   type RouteModel (GenericRoute r opts) = OptModel r opts
   routeEncoder =
     routeEncoder @mr
-      & mapRouteEncoder equality (re subRoutesIso) (subModels @r)
+      & mapRouteEncoder equality (re (subRoutesIso @r) % coercedTo) (subModels @r)
   allRoutes m =
     GenericRoute . review subRoutesIso
       <$> allRoutes (subModels @r m)
diff --git a/src/Ema/Route/Generic/SubRoute.hs b/src/Ema/Route/Generic/SubRoute.hs
index 951c86d..3612f1b 100644
--- a/src/Ema/Route/Generic/SubRoute.hs
+++ b/src/Ema/Route/Generic/SubRoute.hs
@@ -4,7 +4,7 @@
 {-# LANGUAGE UndecidableInstances #-}
 
 module Ema.Route.Generic.SubRoute (
-  HasSubRoutes (SubRoutes, subRoutesIso'),
+  HasSubRoutes (SubRoutes),
   subRoutesIso,
   -- DerivingVia types
   GSubRoutes,
@@ -15,7 +15,7 @@ module Ema.Route.Generic.SubRoute (
 
 import Data.SOP.Constraint (AllZipF)
 import Data.SOP.NS (trans_NS)
-import Ema.Route.Generic.RGeneric (RConstructorNames, RDatatypeName, RGeneric (..))
+import Ema.Route.Generic.RGeneric (RGeneric (..))
 import Ema.Route.Lib.Multi (MultiRoute)
 import GHC.TypeLits (AppendSymbol, Symbol)
 #if MIN_VERSION_GLASGOW_HASKELL(9,2,0,0)
@@ -41,22 +41,15 @@ class HasSubRoutes r where
   -- | The sub-routes in the `r` (for each constructor).
   type SubRoutes r :: [Type]
 
-  type SubRoutes r = GSubRoutes (RDatatypeName r) (RConstructorNames r) (RCode r)
-
-  -- You should use @subRoutesIso@ instead of this function directly.
-  subRoutesIso' :: ((r -> MultiRoute (SubRoutes r)), (MultiRoute (SubRoutes r) -> r))
-  default subRoutesIso' ::
-    ( RGeneric r
-    , ValidSubRoutes r (SubRoutes r)
-    ) =>
-    ((r -> MultiRoute (SubRoutes r)), (MultiRoute (SubRoutes r) -> r))
-  subRoutesIso' =
-    (,) (gtoSubRoutes @r . rfrom) (rto . gfromSubRoutes @r)
-
--- We cannot put this inside the `HasSubRoutes` type-class due to coercion issues with DerivingVia
--- See https://stackoverflow.com/a/71490273/55246
-subRoutesIso :: HasSubRoutes r => Iso' r (MultiRoute (SubRoutes r))
-subRoutesIso = uncurry iso subRoutesIso'
+subRoutesIso ::
+  forall r.
+  ( RGeneric r
+  , HasSubRoutes r
+  , ValidSubRoutes r (SubRoutes r)
+  ) =>
+  Iso' r (MultiRoute (SubRoutes r))
+subRoutesIso =
+  iso (gtoSubRoutes @r . rfrom) (rto . gfromSubRoutes @r)
 
 gtoSubRoutes ::
   forall r subRoutes.