[Interest] QFlags: Typesafe way to check "any flag set"

[Schimkowitsch Robert]

All clear now, thanks!

> -----Original Message-----
> From: Interest <interest-bounces at qt-project.org> On Behalf Of Giuseppe
> D'Angelo via Interest
> Sent: Monday, 23 February 2026 12:23
> To: interest at qt-project.org
> Subject: Re: [Interest] QFlags: Typesafe way to check "any flag set"
>
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> Il 23/02/26 11:52, Schimkowitsch Robert ha scritto:
> > bool isAskingWhen(Question q)
> > {
> >      return {q & QuestionFlag::When};
> > }
> >
> > As you can see in the CE link, this produces a "narrowing" warning, which I
> want to avoid.
>
>
> I guess you have a couple of options here, you could either:
>
> * not put braces at all, or use round braces instead of curly. Round braces just
> group the expression, and are even redundant here.
> Round braces or not, the `q & QuestionFlag::When` expression has type
> QFlags<X>, and it converts to bool via its implicit operator int().
> Curly braces instead trigger copy-list-initialization of the returned bool again
> via the implicit operator int(), but since int->bool is a narrowing conversion,
> and narrowing conversions are invalid in list initializations, then compiler
> warns or rejects the code; or
>
> * use the slightly more expressive/verbose testFlag (or testAnyFlag depending
> on your use case), e.g.
>
>      return q.testFlag(QuestionFlag::When);
>
>
> HTH,
> --
> Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software
> Engineer KDAB (France) S.A.S., a KDAB Group company Tel. France +33 (0)4 90
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