Compiler Hint: “Inline function '…' has not been expanded…”

Question

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

\"H2443 Inline function \'DeleteFile\' has not been expanded because

Answer 1

I was also confused by this hint. Then i realized what the issue is. Your code:

uses
   SysUtils;

procedure TForm1.DoStuff;
begin
   SysUtils.DeleteFile('foo');
end;

is literally being replaced with:

uses
   SysUtils;

procedure TForm1.DoStuff;
var
  Flags, LastError: Cardinal;
begin
  Result := Winapi.Windows.DeleteFile(PChar(FileName));

  if not Result then
  begin
    LastError := GetLastError;
    Flags := GetFileAttributes(PChar(FileName));

    if (Flags <> INVALID_FILE_ATTRIBUTES) and (faSymLink and Flags <> 0) and
      (faDirectory and Flags <> 0) then
    begin
      Result := RemoveDirectory(PChar(FileName));
      Exit;
    end;

    SetLastError(LastError);
  end;
end;

If you'll notice, your "new" code depends on WinApi.Windows unit:

Result := Winapi.Windows.DeleteFile(PChar(FileName));

which you didn't include in your uses clause.

If you manually had inlined the code (copied and pasted), the code would simply not compile until you added Windows to your uses.

Instead, the compiler will not do the inline because:

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