redundant cast: ensure cast is not removed if operand changes it's type

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/redundantCast/RejectReturnTypeChange.java

@@ -0,0 +1,26 @@
+
+import java.util.*;
+import java.util.function.Function;
+
+import static java.util.Collections.emptyList;
+
+class Ambiguous {
+  public void setRoots(List<String> roots) {}
+
+  public static <T> List<T> concat(Iterable<? extends Collection<T>> list) {
+    return new ArrayList<T>();
+  }
+
+  public static <T> List<T> concat(List<List<? extends T>> lists) {
+    return new ArrayList<T>();
+  }
+
+  public static <T,V> List<V> map(Collection<? extends T> iterable, Function<T, V> mapping) {
+    return emptyList();
+  }
+
+  public void anonymousToLambda(HashSet<String> modules) {
+    setRoots(Ambiguous.concat(Ambiguous.map(modules, (Function<String, List<String>>) s -> null)));
+  }
+
+}