added a few 'compiler' tests

Author: jmhofer

rxjava-core/src/main/java/rx/Observable.java

@@ -515,7 +515,7 @@ public static <T> Observable<T> error(Throwable exception) {
      *            emitted by the resulting Observable
      * @return an Observable that emits each item in the source {@link Iterable} sequence
      */
-    public static <T> Observable<T> from(Iterable<T> iterable) {
+    public static <T> Observable<T> from(Iterable<? extends T> iterable) {
         return create(OperationToObservableIterable.toObservableIterable(iterable));
     }
 
@@ -579,7 +579,7 @@ public static Observable<Integer> range(int start, int count) {
      * @return an Observable whose {@link Observer}s trigger an invocation of the given Observable
      *         factory function
      */
-    public static <T> Observable<T> defer(Func0<? extends Observable<T>> observableFactory) {
+    public static <T> Observable<T> defer(Func0<? extends Observable<? extends T>> observableFactory) {
         return create(OperationDefer.defer(observableFactory));
     }
 

rxjava-core/src/test/java/rx/CovarianceTest.java

@@ -1,5 +1,7 @@
 package rx;
 
+import java.util.ArrayList;
+
 import org.junit.Test;
 
 import rx.util.functions.Action1;
@@ -12,6 +14,26 @@
  */
 public class CovarianceTest {
 
+    /**
+     * This won't compile if super/extends isn't done correctly on generics
+     */
+    @Test
+    public void testCovarianceOfFrom() {
+        Observable.<Movie>from(new HorrorMovie());
+        Observable.<Movie>from(new ArrayList<HorrorMovie>());
+        // Observable.<HorrorMovie>from(new Movie()); // may not compile
+    }
+    
+    /**
+     * This won't compile if super/extends isn't done correctly on generics
+     */
+    @Test
+    public void testCovarianceOfMerge() {
+        Observable<HorrorMovie> horrors = Observable.from(new HorrorMovie());
+        Observable<Observable<HorrorMovie>> metaHorrors = Observable.just(horrors);
+        Observable.<Media>merge(metaHorrors);
+    }
+    
     /**
      * This won't compile if super/extends isn't done correctly on generics
      */
@@ -20,51 +42,53 @@ public void testCovarianceOfZip() {
         Observable<HorrorMovie> horrors = Observable.from(new HorrorMovie());
         Observable<CoolRating> ratings = Observable.from(new CoolRating());
 
-        Func2<Media, Rating, ExtendedResult> combine = new Func2<Media, Rating, ExtendedResult>() {
-            @Override
-            public ExtendedResult call(Media m, Rating r) {
-                return new ExtendedResult();
-            }
-        };
-
-        Observable.<Movie, CoolRating, Result> zip(horrors, ratings, combine).toBlockingObservable().forEach(new Action1<Result>() {
-            @Override
-            public void call(Result t1) {
-                System.out.println("Result: " + t1);
-            }
-        });
-
-        Observable.<Movie, CoolRating, Result> zip(horrors, ratings, combine).toBlockingObservable().forEach(new Action1<Result>() {
-            @Override
-            public void call(Result t1) {
-                System.out.println("Result: " + t1);
-            }
-        });
-
-        Observable.<Media, Rating, ExtendedResult> zip(horrors, ratings, combine).toBlockingObservable().forEach(new Action1<ExtendedResult>() {
-            @Override
-            public void call(ExtendedResult t1) {
-                System.out.println("Result: " + t1);
-            }
-        });
-
-        Observable.<Media, Rating, Result> zip(horrors, ratings, combine).toBlockingObservable().forEach(new Action1<Result>() {
-            @Override
-            public void call(Result t1) {
-                System.out.println("Result: " + t1);
-            }
-        });
-
-        Observable.<Media, Rating, ExtendedResult> zip(horrors, ratings, combine).toBlockingObservable().forEach(new Action1<Result>() {
-            @Override
-            public void call(Result t1) {
-                System.out.println("Result: " + t1);
-            }
-        });
-
+        Observable.<Movie, CoolRating, Result> zip(horrors, ratings, combine).toBlockingObservable().forEach(action);
+        Observable.<Movie, CoolRating, Result> zip(horrors, ratings, combine).toBlockingObservable().forEach(action);
+        Observable.<Media, Rating, ExtendedResult> zip(horrors, ratings, combine).toBlockingObservable().forEach(extendedAction);
+        Observable.<Media, Rating, Result> zip(horrors, ratings, combine).toBlockingObservable().forEach(action);
+        Observable.<Media, Rating, ExtendedResult> zip(horrors, ratings, combine).toBlockingObservable().forEach(action);
+        
         Observable.<Movie, CoolRating, Result> zip(horrors, ratings, combine);
     }
 
+    /**
+     * This won't compile if super/extends isn't done correctly on generics
+     */
+    @Test
+    public void testCovarianceOfCombineLatest() {
+        Observable<HorrorMovie> horrors = Observable.from(new HorrorMovie());
+        Observable<CoolRating> ratings = Observable.from(new CoolRating());
+
+        Observable.<Movie, CoolRating, Result> combineLatest(horrors, ratings, combine).toBlockingObservable().forEach(action);
+        Observable.<Movie, CoolRating, Result> combineLatest(horrors, ratings, combine).toBlockingObservable().forEach(action);
+        Observable.<Media, Rating, ExtendedResult> combineLatest(horrors, ratings, combine).toBlockingObservable().forEach(extendedAction);
+        Observable.<Media, Rating, Result> combineLatest(horrors, ratings, combine).toBlockingObservable().forEach(action);
+        Observable.<Media, Rating, ExtendedResult> combineLatest(horrors, ratings, combine).toBlockingObservable().forEach(action);
+        
+        Observable.<Movie, CoolRating, Result> combineLatest(horrors, ratings, combine);
+    }
+
+    Func2<Media, Rating, ExtendedResult> combine = new Func2<Media, Rating, ExtendedResult>() {
+        @Override
+        public ExtendedResult call(Media m, Rating r) {
+            return new ExtendedResult();
+        }
+    };
+
+    Action1<Result> action = new Action1<Result>() {
+        @Override
+        public void call(Result t1) {
+            System.out.println("Result: " + t1);
+        }
+    };
+    
+    Action1<ExtendedResult> extendedAction = new Action1<ExtendedResult>() {
+        @Override
+        public void call(ExtendedResult t1) {
+            System.out.println("Result: " + t1);
+        }
+    };
+    
     static class Media {
     }