From 15e8d83a377398c9c13a5319a23645d10b14579a Mon Sep 17 00:00:00 2001
From: liu fengyun <liu@fengy.me>
Date: Thu, 13 Apr 2017 14:23:47 +0200
Subject: fix #2254: dealias types in decomposition of spaces

---
 compiler/src/dotty/tools/dotc/transform/patmat/Space.scala | 4 ++--
 tests/patmat/i2254.scala                                   | 6 ++++++
 2 files changed, 8 insertions(+), 2 deletions(-)
 create mode 100644 tests/patmat/i2254.scala

diff --git a/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala b/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
index baf1ae356..229545a57 100644
--- a/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -324,7 +324,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
 
     debug.println(s"candidates for ${tp.show} : [${children.map(_.show).mkString(", ")}]")
 
-    tp match {
+    tp.dealias match {
       case OrType(tp1, tp2) => List(Typ(tp1, true), Typ(tp2, true))
       case _ if tp =:= ctx.definitions.BooleanType =>
         List(
@@ -379,7 +379,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
   def canDecompose(tp: Type): Boolean = {
     val res = tp.classSymbol.is(allOf(Abstract, Sealed)) ||
       tp.classSymbol.is(allOf(Trait, Sealed)) ||
-      tp.isInstanceOf[OrType] ||
+      tp.dealias.isInstanceOf[OrType] ||
       tp =:= ctx.definitions.BooleanType ||
       tp.classSymbol.is(allOf(Enum, Sealed))  // Enum value doesn't have Sealed flag
 
diff --git a/tests/patmat/i2254.scala b/tests/patmat/i2254.scala
new file mode 100644
index 000000000..23dd8ad70
--- /dev/null
+++ b/tests/patmat/i2254.scala
@@ -0,0 +1,6 @@
+object Test {
+  type OrAlias = Int | Float
+
+  def m(s: OrAlias | String) = s match {
+    case _: Int => ; case _: Float => ; case _: String => ; }
+}
\ No newline at end of file
-- 
cgit v1.2.3