If a case statement contains all the possible choices (usually in an
enumerated datatype), you can safely remove the when others
clause.
Sigasi Visual HDL warns about this:
Case statement contains all choices explicitly. You can safely remove
the redundant others
.
case bits is
when "00" => -- code
when "01" => -- code
when "10" => -- code
when "11" => -- code
when others => -- never reached: all cases are covered
end case;
There is some debate on this coding rule. However, the vast majority of
synthesis tools do not take the others
into account if all choices are
enumerated. If the synthesis tool is set up to generate fault-tolerant
hardware, the fallback state is the same as the reset state (for most
synthesis tools). Check the manual of your synthesis tools and run some
experiments.
For more information, see VHDL case statements can do without the “others”.
Rule configuration
This rule can be disabled for your project, or its severity and parameters can be modified in the project linting settings. Alternatively, it can be manually configured with the following template:
13/severity/${path}={error|warning|info|ignore}