From 99619d681c571849d0fa072705db6f3490383107 Mon Sep 17 00:00:00 2001
From: mrkkrp <mark.karpov@tweag.io>
Date: Mon, 8 Jul 2019 21:25:05 +0200
Subject: [PATCH] Fix rendering of implicit bidirectional pattern synonyms
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Previously we forgot to enable the extension, and apparently we were just
defining a function called ‘pattern’.
---
 .../value/pattern-synonyms/bidirectional-out.hs      |  4 ++++
 .../value/pattern-synonyms/bidirectional.hs          |  2 ++
 .../explicitely-bidirectional-out.hs                 |  6 ++++++
 .../pattern-synonyms/explicitely-bidirectional.hs    |  4 ++++
 .../value/pattern-synonyms/unidirectional-out.hs     |  2 ++
 .../value/pattern-synonyms/unidirectional.hs         |  2 ++
 src/Ormolu/Printer/Meat/Declaration/Value.hs         | 12 ++++++++----
 7 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/data/examples/declaration/value/pattern-synonyms/bidirectional-out.hs b/data/examples/declaration/value/pattern-synonyms/bidirectional-out.hs
index a4d001a..4577887 100644
--- a/data/examples/declaration/value/pattern-synonyms/bidirectional-out.hs
+++ b/data/examples/declaration/value/pattern-synonyms/bidirectional-out.hs
@@ -1,6 +1,10 @@
+{-# LANGUAGE PatternSynonyms #-}
+
 pattern Arrow t1 t2 = App "->" [t1, t2]
+
 pattern Int =
   App "Int" []
+
 pattern Maybe t =
   App
     "Maybe"
diff --git a/data/examples/declaration/value/pattern-synonyms/bidirectional.hs b/data/examples/declaration/value/pattern-synonyms/bidirectional.hs
index 8c63329..59c35ad 100644
--- a/data/examples/declaration/value/pattern-synonyms/bidirectional.hs
+++ b/data/examples/declaration/value/pattern-synonyms/bidirectional.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE PatternSynonyms #-}
+
 pattern Arrow t1 t2 = App "->"    [t1, t2]
 pattern Int         =
   App "Int"   []
diff --git a/data/examples/declaration/value/pattern-synonyms/explicitely-bidirectional-out.hs b/data/examples/declaration/value/pattern-synonyms/explicitely-bidirectional-out.hs
index fc6e680..a685849 100644
--- a/data/examples/declaration/value/pattern-synonyms/explicitely-bidirectional-out.hs
+++ b/data/examples/declaration/value/pattern-synonyms/explicitely-bidirectional-out.hs
@@ -9,3 +9,9 @@ pattern HeadC' x <-
   x : xs
   where
     HeadC' x = [x]
+
+pattern Simple <-
+  "Simple"
+  where
+    Simple =
+      "Complicated"
diff --git a/data/examples/declaration/value/pattern-synonyms/explicitely-bidirectional.hs b/data/examples/declaration/value/pattern-synonyms/explicitely-bidirectional.hs
index 90fd309..b2ae253 100644
--- a/data/examples/declaration/value/pattern-synonyms/explicitely-bidirectional.hs
+++ b/data/examples/declaration/value/pattern-synonyms/explicitely-bidirectional.hs
@@ -7,3 +7,7 @@ pattern HeadC' x <-
   x:xs
   where
     HeadC' x = [x]
+
+pattern Simple <- "Simple"
+  where
+    Simple = "Complicated"
diff --git a/data/examples/declaration/value/pattern-synonyms/unidirectional-out.hs b/data/examples/declaration/value/pattern-synonyms/unidirectional-out.hs
index 59d7a53..5cf5b8e 100644
--- a/data/examples/declaration/value/pattern-synonyms/unidirectional-out.hs
+++ b/data/examples/declaration/value/pattern-synonyms/unidirectional-out.hs
@@ -4,3 +4,5 @@ pattern Head x <- x : xs
 
 pattern Head' x <-
   x : xs
+
+pattern Simple <- "Simple"
diff --git a/data/examples/declaration/value/pattern-synonyms/unidirectional.hs b/data/examples/declaration/value/pattern-synonyms/unidirectional.hs
index 8155a85..19830b2 100644
--- a/data/examples/declaration/value/pattern-synonyms/unidirectional.hs
+++ b/data/examples/declaration/value/pattern-synonyms/unidirectional.hs
@@ -4,3 +4,5 @@ pattern Head x <- x:xs
 
 pattern Head' x
   <- x:xs
+
+pattern Simple <- "Simple"
diff --git a/src/Ormolu/Printer/Meat/Declaration/Value.hs b/src/Ormolu/Printer/Meat/Declaration/Value.hs
index f3fbbd5..c239005 100644
--- a/src/Ormolu/Printer/Meat/Declaration/Value.hs
+++ b/src/Ormolu/Printer/Meat/Declaration/Value.hs
@@ -575,24 +575,28 @@ p_hsExpr = \case
 p_patSynBind :: PatSynBind GhcPs GhcPs -> R ()
 p_patSynBind PSB {..} = do
   txt "pattern "
+  let nonEmptySynDetails = \case
+        PrefixCon (_:_) -> True
+        RecCon (_:_) -> True
+        _ -> False
   case psb_dir of
     Unidirectional -> do
       p_rdrName psb_id
-      space
+      when (nonEmptySynDetails psb_args) space
       p_patSynDetails psb_args
       txt " <-"
       breakpoint
       inci (located psb_def p_pat)
     ImplicitBidirectional -> do
       p_rdrName psb_id
-      space
+      when (nonEmptySynDetails psb_args) space
       p_patSynDetails psb_args
       txt " ="
       breakpoint
-      located psb_def p_pat
+      inci (located psb_def p_pat)
     ExplicitBidirectional mgroup -> do
       p_rdrName psb_id
-      space
+      when (nonEmptySynDetails psb_args) space
       p_patSynDetails psb_args
       txt " <-"
       breakpoint