Merge pull request #574 from danikov/covariant-future-iterables

bugfix for self-referential loop + test

core/src/main/java/org/jclouds/util/ConcreteFunction.java

@@ -0,0 +1,45 @@
+/**
+ * Licensed to jclouds, Inc. (jclouds) under one or more
+ * contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  jclouds licenses this file
+ * to you 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 org.jclouds.util;
+
+import com.google.common.base.Function;
+
+
+/**
+ * For wrapping covariant functions for passing to non-covariant methods
+ * 
+ * @author danikov
+ */
+public class ConcreteFunction<F,T> implements Function<F, T> {
+   private final Function<? super F, ? extends T> delegate;
+   
+   public static <F,T> ConcreteFunction<F,T> wrap(Function<? super F, ? extends T> delegate) {
+      return new ConcreteFunction<F, T>(delegate);
+   }
+
+   public ConcreteFunction(Function<? super F, ? extends T> delegate) {
+      this.delegate = delegate;
+   }
+
+   @Override
+   public T apply(F input) {
+      return delegate.apply(input);
+   }
+
+}

core/src/test/java/org/jclouds/util/Maps2Test.java

@@ -31,6 +31,7 @@ import org.testng.annotations.Test;
 import com.google.common.base.Function;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 
 /**
@@ -86,4 +87,18 @@ public class Maps2Test {
             }), expected);
    }
    
+   @Test
+   public void testCovariantUniqueIndex() {
+      Iterable<Integer> values = Lists.newArrayList(1, 2, 3, 4, 5);
+      Map<Number, Number> map = Maps2.<Number, Number>uniqueIndex(values, new Function<Object, Double>() {
+
+         @Override
+         public Double apply(Object input) {
+            return (Integer)input + 0.1;
+         }
+      });
+      
+      assertEquals(map.get(1.1), 1);
+   }
+   
 }