Why is this an issue?

All references should have the same case as the corresponding declarations. This is a convention rule since VHDL is not case-sensitive.

How to fix it

Code examples

Noncompliant code example

procedure proc is
  variable tmp : std_ulogic := '0';
  constant cst : std_ulogic := '0';
begin
  tmp <= Cst; -- Noncompliant: Wrong case for identifier "Cst". Should be "cst" instead.
end PROC;     -- Noncompliant: Wrong case for identifier "PROC". Should be "proc" instead.

Compliant solution

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