Delphi since version 2 can tell you about minor errors in your code such as declaring a variable and not using it or writing to a variable and not using the stored value.
By default, the hints and wanings are switched off. You can switch them on
either on a global level (for all units in a project):
To view these hints for an entire project, open the Project Options dialog box, go on the Compiler page and select the Show Hints checkbox.
even within a small section of a given unit. To view only the hints that apply to a section of code, use the {$HINTS ON} and {$HINTS OFF} compiler directives, as shown below:
{$HINTS ON}
procedure aProc;
var
X : Integer;
begin
ShowMessage('X is not used');
end;
{$HINTS OFF}