In a unit I use the function `DeleteFile` and the compiler outputs a hint:

> 
> "H2443 Inline function 'DeleteFile' has not been expanded because unit 'Windows' is not specified in USES list"
> 
> 
> 

In `Uses` there is `SysUtils`, which defines `DeleteFile` (although internally calling `Windows.DeleteFile`).

What does this hint mean? If I put `Windows` into the `Uses` clause, it's gone, but I would like to understand what it is that bothers the compiler.