Fix #209: Add regression test

tests/neg/i209.scala

@@ -0,0 +1,9 @@
+
+case class Foo(a: Int) {
+  private def copy(i: Int): Foo = Foo(2 * i)
+}
+
+object Test {
+  val foo = Foo(2)
+  foo.copy(3) // error
+}

tests/run/i209.scala

@@ -0,0 +1,40 @@
+case class Foo(a: Int) {
+  def copy(i: Int = 9): Foo = Foo(i)
+}
+
+case class Bar(a: Int, b: Int) {
+  def copy(i: Int = 4, j: Int = 6): Bar = Bar(i, j)
+}
+
+case class Baz(a: Int) {
+  def copy(i: Int): Baz = Baz(2 * i)
+}
+
+case class PBaz(a: Int) {
+  private def copy(i: Int): PBaz = PBaz(2 * i)
+  def copy2(i: Int): PBaz = copy(i)
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    val a = Foo(2)
+    assert(a == Foo(2))
+    assert(a.copy(5) == Foo(5))
+    assert(a.copy() == Foo(9))
+
+    val b = Bar(2, 3)
+    assert(b == Bar(2, 3))
+    assert(b.copy(5, 7) == Bar(5, 7))
+    assert(b.copy(5) == Bar(5, 6))
+    assert(b.copy(j = 5) == Bar(4, 5))
+    assert(b.copy() == Bar(4, 6))
+
+    val c = Baz(2)
+    assert(c == Baz(2))
+    assert(c.copy(3) == Baz(6))
+
+    val d = PBaz(2)
+    assert(d == PBaz(2))
+    assert(d.copy2(3) == PBaz(6))
+  }
+}