[fpc-pascal] Strange message about mixed signed expression

[Jürgen Hestermann]

I always wondered why I get a compiler message for the following code snipped:

----------------------------------------------------------------------------
function Match(M,F : UTF8String) : boolean;
var i : Cardinal;

...

if i+length(M)<length(F) then
...

----------------------------------------------------------------------------

For the last code line I get:

unit1.pas(1097,14) Hint: Mixing signed expressions and longwords gives a 64bit result

But where are signed expressions involved?
i is Cardinal (so it cannot be negative) and
the two length-statements can also never be negative.
There is no substraction so why this message?
Anybody knows?

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