Dataflow.java

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

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

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);
}