Fix #2156

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

@@ -848,26 +848,21 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {
 
       val nextBinder = afterTest.asTerm
 
-      def needsOuterTest(patType: Type, selType: Type, currentOwner: Symbol): Boolean = {
+      def outerTestNeeded(implicit ctx: Context): Boolean = {
         // See the test for SI-7214 for motivation for dealias. Later `treeCondStrategy#outerTest`
         // generates an outer test based on `patType.prefix` with automatically dealises.
-        patType.dealias match {
-          case tref @ TypeRef(pre, name) =>
-            (pre ne NoPrefix) && tref.symbol.isClass &&
-            ExplicitOuter.needsOuterIfReferenced(tref.symbol.asClass)
+        expectedTp.dealias match {
+          case tref @ TypeRef(pre: SingletonType, name) =>
+            val s = tref
+            s.symbol.isClass &&
+            ExplicitOuter.needsOuterIfReferenced(s.symbol.asClass)
           case _ =>
             false
         }
       }
 
       override lazy val introducedRebindings = NoRebindings
 
-      def outerTestNeeded = {
-        val np = expectedTp.normalizedPrefix
-        val ts = np.termSymbol
-        (ts ne NoSymbol) && needsOuterTest(expectedTp, testedBinder.info, ctx.owner)
-      }
-
       // the logic to generate the run-time test that follows from the fact that
       // a `prevBinder` is expected to have type `expectedTp`
       // the actual tree-generation logic is factored out, since the analyses generate Cond(ition)s rather than Trees

compiler/src/dotty/tools/io/ClassPath.scala

@@ -242,8 +242,8 @@ abstract class ClassPath {
       case Some((pkg, rest)) =>
         val rep = packages find (_.name == pkg) flatMap (_ findClass rest)
         rep map {
-          case x: ClassRep  => x
-          case x            => throw new FatalError("Unexpected ClassRep '%s' found searching for name '%s'".format(x, name))
+          case x: AnyClassRep => x
+          case x              => throw new FatalError("Unexpected ClassRep '%s' found searching for name '%s'".format(x, name))
         }
       case _ =>
         classes find (_.name == name)
@@ -256,6 +256,7 @@ abstract class ClassPath {
     }
 
   def sortString = join(split(asClasspathString).sorted: _*)
+
   override def equals(that: Any) = that match {
     case x: ClassPath => this.sortString == x.sortString
     case _            => false

tests/run/i2156.scala

@@ -0,0 +1,37 @@
+class Outer {
+
+  case class Inner()
+
+  val inner: Inner = new Inner
+
+  def checkInstance(o: Outer) =
+    o.inner.isInstanceOf[this.Inner]
+
+  def checkPattern1(i: Any) =
+    i match {
+      case _: Inner => true
+      case _ => false
+    }
+
+  def checkPattern2(i: Any) =
+    i match {
+      case Inner() => true
+      case _ => false
+    }
+
+  def checkEquals(o: Outer) =
+    o.inner == inner
+}
+
+object Test {
+
+  def main(args: Array[String]) = {
+    val o1 = new Outer
+    val o2 = new Outer
+    assert(o1.checkInstance(o2)) // ok
+    assert(!o1.checkPattern1(o2.inner)) // ok under scalac, fails for dotc-compiled code
+    assert(!o1.checkPattern2(o2.inner))  // ok under scalac, fails for dotc-compiled code
+    assert(!o1.checkEquals(o2))  // ok under scalac, fails for dotc-compiled code
+  }
+}
+