That needs to be

-sv

AFAICT. You may want to run a simple check in yosys by itself though, because it only supports a subset of system verilog right now.

The corresponding flag for iverilog is -

g2012

. My experience is that the SV yosys subset is mostly covered by iverilog as well.

Also you can bring all your code into one file at the same time making it easier to move around.