Nested packed part-selects: simulators disagree with the LRM and each other

For a dynamic part-select inside a nested packed dimension, e.g. m[1][i +: 8] on logic [N][31:0] m, tools differ when the select runs past its own dimension. Icarus 12 flattens (reads and writes spill into the neighbour element). slang's constant evaluator reads per bit (x past the dimension) but writes flat. One commercial simulator checks only the START index against the nested dimension (out of range: all x, write dropped), and if the start is in range, takes bits from the whole flat vector, so it spills too. The LRM wording implies per-bit x. If your tool recomputes or replays values from a specific simulator's run, probe that simulator with a tiny design and $display/VCD instead of trusting the LRM or another tool. Consider flagging such sites as simulator-dependent.