The method map(Function<? super Role,? extends R>) in the type Stream<Role> is not applicable for the arguments ((<no type> r) -> {})

问题

Why i am getting this error while using GrantedAuthority .

1 CustomUserDetails class.

public class CustomUserDetails extends User implements UserDetails {

    public CustomUserDetails(final User user) {
        super(user);
    }

    @Override
    public Collection<? extends GrantedAuthority> getAuthorities() {
        return getRoles().stream().map( r -> {

            new SimpleGrantedAuthority(r.getRole().name());

        }  ).collect(Collectors.toList());
    }

2. Role class.

   @Entity(name = "ROLE") public class Role { @Id @Column(name = "ROLE_ID") @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id;

   @Column(name = "ROLE_NAME")
   @Enumerated(EnumType.STRING)
   @NaturalId
   private RoleName role;
   
   @ManyToMany(mappedBy = "roles", fetch = FetchType.LAZY)
   @JsonIgnore
   private Set<User> userList = new HashSet<>();
   

来源：https://stackoverflow.com/questions/60118056/the-method-mapfunction-super-role-extends-r-in-the-type-streamrole-is-n