An implicit conversion between types that have different packed array dimensions — even when their total bit width is identical — often indicates a coding error.
Note that this warning will not trigger for types with only a single packed dimension.
module fly; logic [3:1][1:0] a; logic [5:0][1:0] b; initial b = a; endmodule
module fly; logic [5:0][1:0] a; logic [5:0][1:0] b; initial b = a; endmodule