Delphi 10.2 Tokyo introduced a “with” warning: for most “with” statements, W1048 is raised ([RSP-17326] with statements generate W1048 unsafe typecast warning – Embarcadero Technologies)
Posted by jpluimers on 2021/05/05
A cool feature introduced in Delphi 10.2 Tokyo: often [RSP-17326] with statements generate W1048 unsafe typecast warning – Embarcadero Technologies.
Only 2 upvotes, so I assume the “anti with camp” people are finally winning (:
Notes:
- that not all with statements generate a
W1048warning. It looks like the ones using local variables don’t, but parameters, properties and fields to. - when generated, they are always of this form:
W1048 Unsafe typecast of '%s' to 'Pointer' - I only found one other public report searching for “w1048” “to ‘Pointer'” – Google Search:
Quoted from the bug-report (as they cannot be archived in the wayback machine)
with statements generate W1048 unsafe typecast warning
Details
Bug
Reported
Major
Description
All with statements generate this warning. I am on board with the theory that all with statements are inherently somewhat unsafe, but with 1.5 million lines of legacy code (and over 500 new warnings), I would significantly prefer to have a separate warning for with statements.
As it happens I would like to go through and do this work, especially if we can have refactoring to restore non-with code – see RSP-13978. BUT, Godzilla is generating new extra warnings (including unsafe typecasts) in this legacy code and I would prefer to be able to attack these first and attend to with statements later.Activity
Comments
Jira-Quality Sync Service added a comment –
Jason Sprenger requested more info in order to validate the issue and commented: Not any code involving “with” statements produces an unsafe typecast warning.
For instance,
program RS82298; {$APPTYPE CONSOLE} uses System.SysUtils; procedure Use(var X); begin< end; type TMyClass = class FValue: Integer; property Value: Integer read FValue write FValue; end; procedure RunRS82298; var MyClass: TMyClass; begin MyClass := TMyClass.Create; with MyClass do begin Value := 42; end; with MyClass do WriteLn('MyClass.Value=', MyClass.Value); Use(MyClass); end; begin try RunRS82298 except on E: Exception do begin WriteLn('FAIL - Unexpected Exception'); WriteLn(' ClassName=', E.ClassName); WriteLn(' Message=', E.Message); end; end; end.What sort of source involving “with” statements is generating these warnings for you?
With this information our development team can consider addressing your particular circumstance.
Try this (obviously a simple made-up example), and you do need to enable W1048 first in the project options:
program Project18; {$APPTYPE CONSOLE} {$R *.res} uses System.SysUtils; type TAnother = class private FAmbiguous : Boolean; public property Ambiguous : Boolean read FAmbiguous write FAmbiguous; end; TFirst = class private FAnother : TAnother; public procedure Doit; end; var First : TFirst; { TFirst } procedure TFirst.Doit; begin FAnother := TAnother.Create; with FAnother do // WARNING begin Ambiguous := true; end; end; var XAnother : TAnother; begin try XAnother := TAnother.Create; with XAnother do // NO WARNING HERE begin Ambiguous := true; end; except on E: Exception do Writeln(E.ClassName, ': ', E.Message); end; end.
–jeroen
The Wiert Corner - irregular stream of stuff 
Bruce McGee said
Unfortunately, Embarcadero closed my request for a dedicated WITH warning.
https://quality.embarcadero.com/browse/RSP-14063