Due to a problem in the Intel® Quartus® Prime Pro Edition Software version 21.2 and earlier, you might see the following error when a child partition port is not driven by the parent partition and the port name contains a special character like "\":
Internal Error: Sub-system: CDB_SGATE, File: /quartus/db/cdb_sgate/cdb_sgate_partition_boundary_mapping.cpp, Line: 100
To work around this problem, turn off the Design Assistant rule TMC-10115 from the Assignments/Settings menu > Design Assistant Rules Settings window.
This problem is fixed beginning with the Intel® Quartus® Prime Pro Edition Software version 22.1.