makeStaticKind

Utility method for creating a concrete ReportKind out of a list of ReportUnit by reflection.

From a list this of a specific ReportUnit U, build up the specific kind K for it This is done statically, in which all fields are declared at compile time Also if K contains only null fields, return null instead to simplify the checking

Example: when U = PipelineErrorUnit and K = PipelineErrors, all PipelineErrorUnits (e.g. PipelineErrorUnit.NonFatalError, PipelineErrorUnit.FatalError) will be searched from this, and will be used to populate an instance of PipelineErrors, setting the units accordingly.

Works by creating an instance of K and getting all the mutable fields in it; For each subReportUnitType under U (one of sealed subclass of U), filter this for elements of such subReportUnitType to subReportUnits. If there is any of these, further find the corresponding mutable field in the K instance for this subReportUnitType, check whether this field is of type subReportUnitType or List, finally set the field in its type using subReportUnits

Note that the contract between K and subReportUnitType: U is that there is exactly one mutable field using subReportUnitType in K, either of type subReportUnitType? or List<subReportUnitType>?. The contract between subReportUnitType and U is that subReportUnitType must be a sealed subclass of U