@MapperConfig(
    componentModel = "jakarta",
    unmappedTargetPolicy = ReportingPolicy.ERROR,
    injectionStrategy = InjectionStrategy.CONSTRUCTOR,
    nullValueCheckStrategy = NullValueCheckStrategy.ALWAYS,
    nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE)
public class MicronautMappingConfig {}

@Mapper(config = MicronautMappingConfig.class)
public interface NumberousMapper {

    NumberDto toNumberDto(Short shortValue, Integer intValue);

    default int toInt(Number number) {
        return number.intValue();
    }

    default short toShort(Number number) {
        return number.shortValue();
    }
}

class NumberDto {

    private int intValue;
    private short shortValue;

    public int getIntValue() {
        return intValue;
    }

    public void setIntValue(int intValue) {
        this.intValue = intValue;
    }

    public short getShortValue() {
        return shortValue;
    }

    public void setShortValue(short shortValue) {
        this.shortValue = shortValue;
    }
}

NumberousMapper.java:8: error: Ambiguous mapping methods found for mapping property "Integer intValue" to int: int toInt(Number number), short toShort(Number number). See https://mapstruct.org/faq/#ambiguous for more info.
    NumberDto toNumberDto(Short shortValue, Integer intValue);
              ^