checker/tests/nullness/java8/lambda/Dataflow.java

// Test dataflow refinement in the body of a lambda.

import org.checkerframework.checker.nullness.qual.*;

public class Dataflow {
  void context() {
    FunctionDF<@Nullable Object, Object> o =
        a -> {
          // :: error: (dereference.of.nullable)
          a.toString();
          a = "";
          a.toString();
          return "";
        };
  }
}

interface FunctionDF<T extends @Nullable Object, R> {
  R apply(T t);
}