From c9b0d21826c1479ae3c977713b21ccd704b2b95a Mon Sep 17 00:00:00 2001
From: defanor <defanor@uberspace.net>
Date: Sun, 3 Dec 2017 08:12:35 +0300
Subject: Omit constructor names, unless those are in sums

---
 Coalpit.hs | 47 ++++++++++++++++++++++++++++++++++++++---------
 Example.hs | 12 +++++++++---
 2 files changed, 47 insertions(+), 12 deletions(-)

diff --git a/Coalpit.hs b/Coalpit.hs
index ab7edff..4d3bdd0 100644
--- a/Coalpit.hs
+++ b/Coalpit.hs
@@ -47,12 +47,41 @@ instance (GArgParser a, GArgParser b) => GArgParser (a :*: b) where
 instance (GToArgs a, GToArgs b) => GToArgs (a :*: b) where
   gToArgs (a :*: b) = gToArgs a ++ gToArgs b
 
-instance (GArgParser a, GArgParser b) => GArgParser (a :+: b) where
-  gArgParser = L1 <$> gArgParser <|> R1 <$> gArgParser
-
-instance (GToArgs a, GToArgs b) => GToArgs (a :+: b) where
-  gToArgs c@(L1 x) = gToArgs x
-  gToArgs c@(R1 x) = gToArgs x
+instance (Constructor c1, GArgParser f1, GArgParser (f :+: g)) =>
+  GArgParser ((f :+: g) :+: C1 c1 f1) where
+  gArgParser =
+    L1 <$> gArgParser
+    <|>
+    R1 <$> (string (conName (undefined :: C1 c1 f a)) *> space *> gArgParser)
+
+instance (Constructor c1, GArgParser f1, GArgParser (f :+: g)) =>
+  GArgParser (C1 c1 f1 :+: (f :+: g)) where
+  gArgParser =
+    L1 <$> (string (conName (undefined :: C1 c1 f a)) *> space *> gArgParser)
+    <|>
+    R1 <$> gArgParser
+
+instance (Constructor c1, Constructor c2, GArgParser f1, GArgParser f2) =>
+  GArgParser (C1 c1 f1 :+: C1 c2 f2) where
+  gArgParser =
+    L1 <$> (string (conName (undefined :: C1 c1 f a)) *> space *> gArgParser)
+    <|>
+    R1 <$> (string (conName (undefined :: C1 c2 f a)) *> space *> gArgParser)
+
+instance (Constructor c1, GToArgs f1, GToArgs (f :+: g)) =>
+  GToArgs ((f :+: g) :+: C1 c1 f1) where
+  gToArgs (L1 x) = gToArgs x
+  gToArgs (R1 x) = conName x : gToArgs x
+
+instance (Constructor c1, GToArgs f1, GToArgs (f :+: g)) =>
+  GToArgs (C1 c1 f1 :+: (f :+: g)) where
+  gToArgs (L1 x) = conName x : gToArgs x
+  gToArgs (R1 x) = gToArgs x
+
+instance (Constructor c1, Constructor c2, GToArgs f1, GToArgs f2) =>
+  GToArgs (C1 c1 f1 :+: C1 c2 f2) where
+  gToArgs (L1 x) = conName x : gToArgs x
+  gToArgs (R1 x) = conName x : gToArgs x
 
 instance {-#OVERLAPPING#-}
   (ArgParser a, Selector c) => GArgParser (S1 c (Rec0 (Maybe a))) where
@@ -81,13 +110,13 @@ instance {-#OVERLAPPING#-}
 instance (GToArgs a, Selector c) => GToArgs (S1 c a) where
   gToArgs s@(M1 x) = case selName s of
                          "" -> gToArgs x
-                         name -> ("--" ++ selName s) : gToArgs x
+                         name -> ("--" ++ name) : gToArgs x
 
 instance (GArgParser a, Constructor c) => GArgParser (C1 c a) where
-  gArgParser = string (conName (undefined :: C1 c a f)) *> space *> (M1 <$> gArgParser)
+  gArgParser = M1 <$> gArgParser
 
 instance (GToArgs a, Constructor c) => GToArgs (C1 c a) where
-  gToArgs c@(M1 x) = conName c : gToArgs x
+  gToArgs c@(M1 x) = gToArgs x
 
 
 instance (GArgParser a, Datatype c) => GArgParser (D1 c a) where
diff --git a/Example.hs b/Example.hs
index a9f50aa..0319bcd 100644
--- a/Example.hs
+++ b/Example.hs
@@ -17,13 +17,19 @@ data Foo = Bar Int
          | Qux (Maybe Int) (Maybe Int) RecTest (Maybe Double)
   deriving (Generic, Show)
 
-instance ToArgs Foo
 instance ArgParser Foo
+instance ToArgs Foo
+
+data Wrap = Wrap { foo :: Maybe Foo, num :: Maybe Int }
+  deriving (Generic, Show)
+
+instance ArgParser Wrap
+instance ToArgs Wrap
 
 main :: IO ()
 main = do
-  let val = Qux Nothing (Just 1) (RecTest Nothing (Just 2.3) Nothing) Nothing
+  let val = Wrap (Just $ Qux Nothing (Just 1) (RecTest Nothing (Just 2.3) Nothing) Nothing) (Just 1)
       a = args val
   print val
   putStrLn a
-  print $ parse (argParser :: Parser Foo) "test" a
+  print $ parse (argParser :: Parser Wrap) "test" a
-- 
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