cast warning with -Xlint enabled (becomes error with -Werror)

[mikewacker]

Here is a minimalistic interface that will repro the issue.

@Value.Immutable
@JsonSerialize(as = ImmutableExample.class)
@JsonDeserialize(as = ImmutableExample.class)
public interface Example {

    final class Builder extends ImmutableExample.Builder {}
}

Here's the warning(/error with -Werror enabled):

warning: [cast] redundant cast to ImmutableExample
    return (ImmutableExample) builder.build();

You need both the JSON annotations and the Builder class to trigger this warning.

---

Here's the offending generated snippet:

  @Deprecated
  @JsonCreator(mode = JsonCreator.Mode.DELEGATING)
  static ImmutableExample fromJson(Json json) {
    Example.Builder builder = new Example.Builder();
    return (ImmutableExample) builder.build();
  }

builder.build() actually returns an ImmutableExample, not an Example. Hence, the cast is redundant.

If you remove the Builder class from Example, the snippet looks like this instead:

  @Deprecated
  @JsonCreator(mode = JsonCreator.Mode.DELEGATING)
  static ImmutableExample fromJson(Json json) {
    ImmutableExample.Builder builder = ImmutableExample.builder();
    return builder.build();
  }

See also #672; @SuppressWarnings({"all"}) does not suppress -Xlint warnings for some reason.

In this case, it should be fairly easy to fix this, and the cast warning is probably not one you want to disable. (Whereas the processing warning in #672 is often one that gets disabled anyway.)

[mikewacker]

There is a workaround:

Apply overshadowImplementation = true as part of a @Value.Style. (Which may be a good idea anyway.)

[xenoterracide]

same or related, and overshadow didn't help

/home/xeno/IdeaProjects/spring-app-commons/module/jpa-security/build/generated/sources/annotationProcessor/java/testFixtures/com/xenoterracide/model/security/UserTestDataBuilder.java:54: warning: [cast] redundant cast to Optional<String>
    this.name = (Optional<String>) Objects.requireNonNull(name, "name");

@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
@Value.Style(typeBuilder = "*TestDataBuilder", newBuilder = "create", jakarta = true, overshadowImplementation = true)
final class UserTestDataBuilders {

  private UserTestDataBuilders() {}

  @Builder.Factory
  static User user(@Nonnull Optional<String> name

perhaps the simplest upfront way would simply be to add a SuppressWarnings("cast") to the top of the generated class?