I configured Intellij to use checkerframework @Nullable and @NonNull annotation but I can’t get the inspections to generate an error or a warning at the indicated line (without specifically annotating it with @NonNull.

public interface MyInterface {
    
    /**
     * @return whatever I expect this to be considered @NonNull
     */
    String getWhatever();
}

// ...
import org.checkerframework.checker.nullness.qual.Nullable;


public class MyClass implements MyInterface {

    /** I expect this to be considered @NonNull */
    private final /*@NonNull*/ String whatever;

    /**
     * @param whatever I expect this to be considered @NonNull
     */
    public MyClass(String whatever) {
        // *************************************
        // I expect an error (or warning) on the 
        // next line while assigning a nullable 
        // value to a non null field.
        // *************************************
        this.whatever = validateWhatever(whatever);
    }

    @Override
    public String getWhatever() {
        return whatever;
    }

    /**
     * @param whatever
     * @return whatever or null on error.
     */
    private static @Nullable String validateWhatever(String whatever) {
        try {
            // do something
            return whatever;
        } catch (Exception e) {
            return null;
        }
    }
}