From 7eee1bdcd955ccb26a7328501e853b08cbb140d1 Mon Sep 17 00:00:00 2001
From: Albert Meltzer <7529386+kitbellew@users.noreply.github.com>
Date: Mon, 14 Sep 2020 07:54:48 -0700
Subject: [PATCH] RedundantParens: check if postfix only is allowed

---
 .../org/scalafmt/rewrite/RedundantParens.scala      | 13 +++++++++++--
 .../src/test/resources/rewrite/RedundantParens.stat |  7 +++++--
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/scalafmt-core/shared/src/main/scala/org/scalafmt/rewrite/RedundantParens.scala b/scalafmt-core/shared/src/main/scala/org/scalafmt/rewrite/RedundantParens.scala
index bd6fc59e3d..5d12a3bc44 100644
--- a/scalafmt-core/shared/src/main/scala/org/scalafmt/rewrite/RedundantParens.scala
+++ b/scalafmt-core/shared/src/main/scala/org/scalafmt/rewrite/RedundantParens.scala
@@ -28,9 +28,9 @@ class RedundantParens(implicit ctx: RewriteCtx) extends RewriteSession {
   private[rewrite] val rewriteFunc: PartialFunction[Tree, Unit] = {
     case t @ (_: Term.Tuple | _: Type.Tuple | _: Lit.Unit) => remove(t, 2)
 
-    case g: Enumerator.Guard => remove(g.cond)
+    case g: Enumerator.Guard => maybeRemovePostfix(g.cond)
 
-    case t: Case => t.cond.foreach(remove(_))
+    case t: Case => t.cond.foreach(maybeRemovePostfix)
 
     case t if usesAvoidInfix && t.parent.exists {
           case p: Term.ApplyInfix => p.lhs ne t
@@ -75,6 +75,15 @@ class RedundantParens(implicit ctx: RewriteCtx) extends RewriteSession {
       case _ => remove(tree, minToKeep)
     }
 
+  // https://www.scala-lang.org/files/archive/spec/2.13/06-expressions.html#prefix-infix-and-postfix-operations
+  private def maybeRemovePostfix(tree: Tree): Unit =
+    tree match {
+      case _: Lit | _: Term.Name | _: Term.ApplyInfix | _: Term.Select |
+          _: Term.Apply | _: Term.ApplyUnary =>
+        remove(tree)
+      case _ =>
+    }
+
   private def remove(tree: Tree, minToKeep: Int = 0): Unit =
     removeByTokens(tree.tokens, minToKeep)
 
diff --git a/scalafmt-tests/src/test/resources/rewrite/RedundantParens.stat b/scalafmt-tests/src/test/resources/rewrite/RedundantParens.stat
index 6654f33797..e283a7d1ca 100644
--- a/scalafmt-tests/src/test/resources/rewrite/RedundantParens.stat
+++ b/scalafmt-tests/src/test/resources/rewrite/RedundantParens.stat
@@ -315,11 +315,14 @@ object a {
   }
 }
 >>>
-test does not parse
 object a {
   val b = c match {
     case true if (d match {
-                  ^
+          case true  => true
+          case false => false
+        }) =>
+  }
+}
 <<< #2194 2 infix
 object a {
   val b = c match {