From f3888c2b3a8fad65ca0ed0a77f76859639c88dd8 Mon Sep 17 00:00:00 2001
From: Allan Renucci <allan.renucci@gmail.com>
Date: Wed, 18 Apr 2018 15:49:40 +0200
Subject: [PATCH] Fix #4339: Dealias when checking refinements

---
 .../tools/dotc/transform/ExpandSAMs.scala     |  2 +-
 tests/neg/i4339.scala                         | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 tests/neg/i4339.scala

diff --git a/compiler/src/dotty/tools/dotc/transform/ExpandSAMs.scala b/compiler/src/dotty/tools/dotc/transform/ExpandSAMs.scala
index ef1aca47af89..aa269beea170 100644
--- a/compiler/src/dotty/tools/dotc/transform/ExpandSAMs.scala
+++ b/compiler/src/dotty/tools/dotc/transform/ExpandSAMs.scala
@@ -88,7 +88,7 @@ class ExpandSAMs extends MiniPhase {
     cpy.Block(tree)(List(applyDef, isDefinedAtDef), anonCls)
   }
 
-  private def checkRefinements(tpe: Type, pos: Position)(implicit ctx: Context): Type = tpe match {
+  private def checkRefinements(tpe: Type, pos: Position)(implicit ctx: Context): Type = tpe.dealias match {
     case RefinedType(parent, name, _) =>
       if (name.isTermName && tpe.member(name).symbol.ownersIterator.isEmpty) // if member defined in the refinement
         ctx.error("Lambda does not define " + name, pos)
diff --git a/tests/neg/i4339.scala b/tests/neg/i4339.scala
new file mode 100644
index 000000000000..58150bcb5f74
--- /dev/null
+++ b/tests/neg/i4339.scala
@@ -0,0 +1,19 @@
+class Test {
+  def test: Unit = {
+    val a: PartialFunction[Int, Int]{ def foo: Int } = { case x => x } // error
+
+    type PF = PartialFunction[Int, Int] { def foo: Int }
+    val b: PF = { case x => x } // error
+
+    type PF1 = PartialFunction[Int, Int] {def foo: Int }
+    val c: PF1 {} = { case x => x } // error
+
+    type PF2 = PartialFunction[Int, Int]
+    val d: PF2 {} = { case x => x }
+
+    type PF3 = PartialFunction[Int, Int] {}
+    val e: PF3 = { case x => x }
+
+    val f: PartialFunction[Int, Int] {} { def foo: Int } = { case x => x } // error
+  }
+}