From 7e138cc15a29b09b77551db9d6e92e841fd0d197 Mon Sep 17 00:00:00 2001
From: liu fengyun <liu@fengy.me>
Date: Fri, 24 Nov 2017 17:01:06 +0100
Subject: [PATCH 1/2] Fix #3548: set outer select type to be the type enclosing
 the expected type

Otherwise, ElimOuterSelect will insert `ensureConforms(tp)` in outer test,
which causes run-time exeception.
---
 .../tools/dotc/transform/PatternMatcher.scala |  2 +-
 tests/run/i3548.scala                         | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 tests/run/i3548.scala

diff --git a/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala b/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
index a562410b262c..1ca2635eb6a5 100644
--- a/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
+++ b/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
@@ -771,7 +771,7 @@ object PatternMatcher {
             val expectedClass = expectedTp.dealias.classSymbol.asClass
             ExplicitOuter.ensureOuterAccessors(expectedClass)
             scrutinee.ensureConforms(expectedTp)
-              .outerSelect(1, expectedOuter.tpe.widen)
+              .outerSelect(1, expectedClass.owner.typeRef)
               .select(defn.Object_eq)
               .appliedTo(expectedOuter)
           }
diff --git a/tests/run/i3548.scala b/tests/run/i3548.scala
new file mode 100644
index 000000000000..7d0d47a87269
--- /dev/null
+++ b/tests/run/i3548.scala
@@ -0,0 +1,19 @@
+trait Common {
+  case class Data(a: String)
+}
+object O1 extends Common
+object O2 extends Common
+
+object Test {
+  def main(args: Array[String]): Unit = {
+
+    val data = O2.Data("test")
+
+    // Runtime error: java.lang.ClassCastException: O2$ cannot be cast to O1$
+    data match {
+        case O1.Data(s) => println("O1 data")
+        case O2.Data(s) => println("O2 data")
+        case _ => println("Unknown")
+    }
+  }
+}
\ No newline at end of file

From 37dca3b1b73f0fc84f9662fd3d49c0249f59b1f2 Mon Sep 17 00:00:00 2001
From: liu fengyun <liu@fengy.me>
Date: Fri, 24 Nov 2017 17:23:39 +0100
Subject: [PATCH 2/2] address review: update test

---
 tests/run/i3548.scala | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/tests/run/i3548.scala b/tests/run/i3548.scala
index 7d0d47a87269..5dc6739934b8 100644
--- a/tests/run/i3548.scala
+++ b/tests/run/i3548.scala
@@ -9,11 +9,12 @@ object Test {
 
     val data = O2.Data("test")
 
-    // Runtime error: java.lang.ClassCastException: O2$ cannot be cast to O1$
-    data match {
-        case O1.Data(s) => println("O1 data")
-        case O2.Data(s) => println("O2 data")
-        case _ => println("Unknown")
+    val result = data match {
+      case O1.Data(s) => 1
+      case O2.Data(s) => 2
+      case _ => 3
     }
+
+    assert(result == 2)
   }
 }
\ No newline at end of file