Fix scala#1463: add test

Author: liufengyun

tests/run/i1463.scala

@@ -0,0 +1,26 @@
+object Test {
+  case object Bob { override def equals(other: Any) = true }
+
+  class Bob2 {
+    override def equals(other: Any) = true
+  }
+  val Bob2 = new Bob2
+
+  def f0(x: Any) = x match { case Bob2 => Bob2 } // class cast exception at runtime, dotc only
+  def f1(x: Any) = x match { case Bob => Bob } // class cast exception at runtime, dotc only
+  def f2(x: Any): Bob.type = x match { case x @ Bob => x } // class cast exception at runtime, dotc and javac.
+
+  def main(args: Array[String]): Unit = {
+    assert(f0(Bob2) eq Bob2)
+    assert(f0(0) eq Bob2)  // only dotty fails here
+    assert(f0(Nil) eq Bob2)
+
+    assert(f1(Bob) eq Bob)
+    assert(f1(0) eq Bob)  // only dotty fails here
+    assert(f1(Nil) eq Bob)
+
+    assert(f2(Bob) eq Bob)
+    // assert(f2(0) eq Bob) // both dotty and scalac fail here
+    // assert(f2(Nil) eq Bob)
+  }
+}