added test case for KT-1646 in an attempt to implement lazy filter/flatMap for Iterator

libraries/stdlib/src/Iterators.kt

@@ -1,4 +1,4 @@
-package kotlin.util
+package kotlin
 
 import kotlin.support.AbstractIterator
 
@@ -9,7 +9,7 @@ import java.util.Iterator
 inline fun <T, R: T> java.util.Iterator<T>.filterIsInstance(klass: Class<R>): Iterator<R> = FilterIsIterator<T,R>(this, klass)
 
 private class FilterIsIterator<T, R :T>(val iter: java.util.Iterator<T>, val klass: Class<R>) : AbstractIterator<R>() {
-    override fun computeNext(): R? {
+    override protected fun computeNext(): R? {
         while (iter.hasNext()) {
             val next = iter.next()
             if (klass.isInstance(next)) {
@@ -21,37 +21,46 @@ private class FilterIsIterator<T, R :T>(val iter: java.util.Iterator<T>, val kla
     }
 }
 
+
+// TODO when we're past the compiler error
+// http://youtrack.jetbrains.com/issue/KT-1646
+//
+// we can use this code to replace the other
+// filter / FilterIterator class as it reuses the
+// core logic from AbstractIterator
+
 /** Returns a new lazy iterator containing all elements in this iteration which match the given predicate */
-/*
-inline fun <T> java.util.Iterator<T>.filter(predicate: (T)-> Boolean) : java.util.Iterator<T> {
-    return FilterIterator(this, predicate)
+inline fun <T> java.util.Iterator<T>.filter2(predicate: (T)-> Boolean) : java.util.Iterator<T> {
+    return FilterIterator2(this, predicate)
 }
 
-private class FilterIterator<T>(val iter: java.util.Iterator<T>, val predicate: (T)-> Boolean) : AbstractIterator<T>() {
-    override fun computeNext(): T? {
+private class FilterIterator2<T>(val iter: java.util.Iterator<T>, val fn: (T)-> Boolean) : AbstractIterator<T>() {
+    override protected fun computeNext(): T? {
+        /*
+
+        TODO this block generates a compiler error:
+        http://youtrack.jetbrains.com/issue/KT-1646
+
         while (iter.hasNext()) {
-            val next = iter.next()
-            if (predicate(next)) {
-                return next
+            val element = iter.next()
+            if (fn(element)) {
+                return element
             }
         }
+        */
         done()
         return null
     }
 }
-*/
 
 /** Returns a new lazy iterator containing all elements in this iteration which do not match the given predicate */
-    /*
-    inline fun <T> java.util.Iterator<T>.filterNot(predicate: (T)-> Boolean) : java.util.Iterator<T> {
-        return filter {
-            !predicate(it)
-        }
+inline fun <T> java.util.Iterator<T>.filterNot(predicate: (T)-> Boolean) : java.util.Iterator<T> {
+    return filter {
+        !predicate(it)
     }
-    */
+}
 
 /** Returns a new lazy iterator containing all the non null elements in this iteration */
-/*
 inline fun <T> java.util.Iterator<T?>?.filterNotNull() : java.util.Iterator<T> = FilterNotNullIterator(this)
 
 private class FilterNotNullIterator<T>(val iter: java.util.Iterator<T?>?) : AbstractIterator<T>() {
@@ -68,7 +77,6 @@ private class FilterNotNullIterator<T>(val iter: java.util.Iterator<T?>?) : Abst
         return null
     }
 }
-*/
 
 
 /**
@@ -76,6 +84,9 @@ private class FilterNotNullIterator<T>(val iter: java.util.Iterator<T?>?) : Abst
   * are concatenated together into a single collection
   */
 /*
+
+  TODO implement a lazy flatMap
+
 inline fun <T, R> java.util.Iterator<T>.flatMap(transform: (T)-> java.util.Iterator<R>) : Collection<R> {
     return flatMapTo<>(ArrayList<R>(), transform)
 }