Why is this an issue?

All declared elements should be used in their corresponding scope. Useless declarations should be removed.

How to fix it

Code examples

Noncompliant code example

procedure proc is
  variable tmp: std_logic;
  constant cst: std_logic := '0';
  constant other_cst: std_logic := '1'; -- Noncompliant: "other_cst" is not used
begin
  tmp <= cst;
end proc;

Compliant solution

procedure proc is
  variable tmp: std_logic;
  constant cst: std_logic := '0';
begin
  tmp <= cst;
end proc;