Local/inner types

examples/src/PolymorphicClassObjects.jetl

@@ -0,0 +1,31 @@
+virtual class Builder<E, R> {
+  [operator] fun plusAssign(item : E)
+  fun result() : R
+}
+
+virtual class Buildable {
+  fun newBuilder<E, R>() : Builder<E, R>
+}
+
+class List<T> {
+
+  class object Buildable {
+    override fun newBuilder<E, R>() : Builder<E, R>
+
+  }
+
+}
+
+extension Map<E> for T
+  where
+    T : Iterable<E>,
+    class object T : Buildable<E, T> {
+
+  fun map<R>(f : {(E) : R}) : T<R> = {
+    val builder = T.newBuilder()
+    for (e in this) {
+      builder += f(e)
+    }
+    builder.result()
+  }
+}