Description
I would like to request a feature. I was recently helping a junior engineer to debug a mysterious error that he was struggling with. After searching high and low, we discovered that they had used to instead of downto when defining a range, resulting in a null range, which was only caused a cryptic error message from the simulation tool several layers down in the hierarchy.
I understand that use of null ranges is valid VHDL and I understand if you don't want to create warnings on valid code, but I think that it would helpful to have a warning shown in cases like this, perhaps one that can be suppressed by the user (or even, is suppressed by default and can be un-suppressed by the user) for people who want to use null ranges?
Specifically, I would like to see warnings on X to Y and Y downto X, where X < Y in both cases, e.g.
library IEEE;
use IEEE.std_logic_1164.all;
package test is
subtype null_range_to is integer range 1 to 0;
subtype null_range_downto is integer range 0 downto 1;
subtype slv_null_range_to is std_logic_vector(1 to 0);
subtype slv_null_range_downto is std_logic_vector(0 downto 1);
end package test;