Description
In the Quartus® Prime Pro Edition Software version 18.0, this error message may be seen after running the write_sdc -expand command on a session that had included the derive_pll_clocks directive. The Timing Analyzer will incorrectly infer the unsupported get_combs collection.
Resolution
To work around this problem, substitute all get_combs for get_nodes in the resulting sdc file after executing the write_sdc -expand command.
This problem is scheduled to be fixed in a future release of the Quartus® Prime Pro Edition Software.