Merge pull request #3551 from dotty-staging/fix-3548

Fix #3548: set outer select type to be the type enclosing the expected type

Author: odersky

compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala

@@ -796,7 +796,7 @@ 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)
           }

tests/run/i3548.scala

@@ -0,0 +1,20 @@
+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")
+
+    val result = data match {
+      case O1.Data(s) => 1
+      case O2.Data(s) => 2
+      case _ => 3
+    }
+
+    assert(result == 2)
+  }
+}