Unexpected warning: ''.'' should not be used as a source

I often have a use-case when "." is a valid and correct source of my mapping. It is officially supported mapping source, so why the plugin reports it as "should not be used"? Is there any particular reason or maybe it is just a historical burden from the times when MapStruct actually didn't support "." as a source?

Example:

record Failure(String code, String detail) {}

class Foo {
  Failure failure;
}

class FooDto {
  String failureCode;
  String failureDetail;
}

public abstract class FooMapper {

  @Mapping(target = "failure", source = ".")
  public abstract Foo fromDto(FooDto fooDto);

  protected Failure mapFailure(FooDto fooDto) {
    return new Failure(fooDto.getFailureCode(), fooDto.getFailureDetail());
  }

}

Of course, in this particular case we can just use:

@Mapping(target = "failure.code", source = "failureCode")
@Mapping(target = "failure.detail", source = "failureDetail")

But there are more complex cases when the target object should be created manually, by a custom code, and the only possible source is the whole source object.

Beginne damit, die Warnung anhand des FooMapper-Beispiels zu reproduzieren, und untersuche, wie das MapStruct IntelliJ plugin mit @Mapping-Werten umgeht, deren source "." ist. Vergleiche dieses Verhalten mit der dokumentierten Unterstützung von MapStruct für diese source-Form; abgeschlossen ist die Aufgabe, wenn die gültige Zuordnung nicht mehr fälschlicherweise gewarnt wird oder der Grund für die Warnung eindeutig festgestellt ist.