Why is this an issue?

Using multiple times the same name for different variables is confusing. Names should be unique and should describe the functionality.

How to fix it

Code examples

Noncompliant code example

File 1:
architecture fly of dream is
  variable fly : std_logic;
begin
  ...
end;

File 2:
architecture slide of ice is
  variable fly : std_logic;
begin
  ...
end;

Compliant solution

File 1:
architecture fly of dream is
  variable fly : std_logic;
begin
  ...
end;

File 2:
architecture slide of ice is
  variable dream : std_logic;
begin
  ...
end;