Enums.java

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

public class Enums {

    enum MyEnum {
        A,
        B,
        C,
        D
    }
    //:: error: (assignment.type.incompatible)
    MyEnum myEnum = null; // invalid
    @Nullable MyEnum myNullableEnum = null;

    void testLocalEnum() {
        // Enums are allowed to be null:  no error here.
        MyEnum myNullableEnum = null;
        //:: error: (assignment.type.incompatible)
        @NonNull MyEnum myEnum = null; // invalid
    }
}