Changed hasBackupRestoreFacilities for GeometryGrid [bugfix]

Simon Praetoriusrequested to merge
simon.praetorius/dune-grid:issue/geometrygrid_backuprestore_coordfunction into master

Summary

Changes GeometryGrid capabilities to be true for hasBackupRestoreFacilities only if the CoordFunction is default constructible

Details

Instantiating the BackupRestoreFacilities::restore for GeometryGrid<HostGrid, CoordFunction> with a CoordFunction that is not default constructible leads to an error. This is in contrast to the capability hasBackupRestoreFacilities that returns true for this grid.

This MR updates the capabilities to be false if the CoordsFunction is not default constructible and adds a tag-dispatching with a runtime-error in case someone instantiates the BackupRestoreFacilities with such a CoordsFunction nevertheless.

So, the BackupRestoreFacilities can be instantiated without a compile-time error and one can use the hasBackupRestoreFacilities for a compile-time check whether this should work or not.

See Also

Some discussions about how to restore a non-default-constructible CoordFunction can be found in !339 (closed)

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