added a demonstration of how Kotlin currently handles nullable collections on for loops - by throwing NPEs

runtests/test/stdlib/testall/LanguageTestAllTest.java

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+/*
+ * Copyright 2010-2012 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package stdlib.testall;
+
+import junit.framework.TestSuite;
+import test.language.*;
+
+/**
+ */
+public class LanguageTestAllTest {
+  public static TestSuite suite() {
+    return new TestSuite(NullableCollectionsTest.class);
+  }
+}

testlib/test/language/NullableCollectionsTest.kt

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+package test.language
+
+import junit.framework.TestCase
+import java.util.Collection
+import stdhack.test.*
+
+class NullableCollectionsTest : TestCase() {
+
+    fun testIterateOverNullCollectionsThrowsNPE() {
+        val c: Collection<String>? = null
+
+        // TODO currently this will throw a NPE
+        // should it either be a compile error or handle nulls gracefully?
+        failsWith<NullPointerException> {
+            for (e in c) {
+                println("Hey got $e")
+            }
+        }
+    }
+}