Why is this an issue?

Choices overlaps hid functional issues because some branches cannot be reached. Choices overlaps should be checked at and fixed.

How to fix it

Code examples

Noncompliant code example

X : in integer range 7 downto 0;
...
case X is
  when 0 =>
     Z <= A;
  when 0 to 6 => -- Noncompliant: '0' overlaps preceding when clause
     Z <= B;
  when 1 | 7 => -- Noncompliant: '1' overlaps preceding when clause
     Z <= C;
end case;

Compliant solution

X : in integer range 7 downto 0;
...
case X is
  when 0 =>
     Z <= A;
  when 1 to 6 =>
     Z <= B;
  when  7 =>
     Z <= C;
end case;