From e16271ee0a48b1a23384aa7c76b45cc750e6eada Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Sun, 31 Dec 2017 15:35:16 +0100
Subject: [PATCH 1/2] Define topLevelClass for NoDenotation

Fixes #3647
---
 .../tools/dotc/core/SymDenotations.scala      | 13 +++++++-----
 tests/pos/i3647.scala                         | 21 +++++++++++++++++++
 2 files changed, 29 insertions(+), 5 deletions(-)
 create mode 100644 tests/pos/i3647.scala

diff --git a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
index 18ff1ab41dca..4d85b10a5673 100644
--- a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -925,11 +925,14 @@ object SymDenotations {
     /** The top-level class containing this denotation,
      *  except for a toplevel module, where its module class is returned.
      */
-    final def topLevelClass(implicit ctx: Context): Symbol = {
-      def topLevel(d: SymDenotation): Symbol = {
-        if (d.isEffectiveRoot || (d is PackageClass) || (d.owner is PackageClass)) d.symbol
-        else topLevel(d.owner)
-      }
+    def topLevelClass(implicit ctx: Context): Symbol = {
+
+      def topLevel(d: SymDenotation): Symbol =
+        if (!exists || d.isEffectiveRoot || (d is PackageClass) || (d.owner is PackageClass))
+          d.symbol
+        else
+          topLevel(d.owner)
+
       val sym = topLevel(this)
       if (sym.isClass) sym else sym.moduleClass
     }
diff --git a/tests/pos/i3647.scala b/tests/pos/i3647.scala
new file mode 100644
index 000000000000..5bad3d5beb63
--- /dev/null
+++ b/tests/pos/i3647.scala
@@ -0,0 +1,21 @@
+object App {
+  def main(args: Array[String]): Unit = {
+    trait FooT {
+      type T
+      type Bar[A]
+
+      def get(k: Bar[T]): String
+    }
+    val test: FooT = new FooT {
+      type T = String
+      type Bar[A] = J[A]
+      sealed abstract class J[A]
+      final case object JName extends J[T]
+      final case object JInt extends J[Int]
+
+      def get(k: J[T]): String = k match {
+        case JName => "Age"
+      }
+    }
+  }
+}

From a84e4019b3c2fd845f74647928ace3f8d54cd729 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Tue, 2 Jan 2018 01:48:33 +0100
Subject: [PATCH 2/2] Make topLevelClass final again

---
 compiler/src/dotty/tools/dotc/core/SymDenotations.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
index 4d85b10a5673..17390f830ecf 100644
--- a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -925,7 +925,7 @@ object SymDenotations {
     /** The top-level class containing this denotation,
      *  except for a toplevel module, where its module class is returned.
      */
-    def topLevelClass(implicit ctx: Context): Symbol = {
+    final def topLevelClass(implicit ctx: Context): Symbol = {
 
       def topLevel(d: SymDenotation): Symbol =
         if (!exists || d.isEffectiveRoot || (d is PackageClass) || (d.owner is PackageClass))