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List:       kde-devel
Subject:    Re: Challenge: adding new method overloads when existing consumers use {} with args
From:       Thiago Macieira <thiago () kde ! org>
Date:       2022-07-27 23:38:50
Message-ID: 7546046.lvqk35OSZv () tjmaciei-mobl5
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On Wednesday, 27 July 2022 14:37:20 PDT Friedrich W. H. Kossebau wrote:
> * new overload method (and any further ones) will stay special
> * existing consumer code using {} is not that simple to map by human readers
> as to which overload will be used
> * needs C++17, so needs some additional markup when used in KF5 headers for
> those using them with C++11-compat needs

You can use std::enable_if (no _t).

Another trick is what we do in Qt with Q_WEAK_OVERLOAD: 

template <typename = void>

It doesn't matter what the parameters are and that this new template function 
doesn't actually use the template parameter. As a template function, it will 
not get selected for conversion; the types must match exactly.

This is handy even without {}, when you want to down-prioritise some overloads 
over others for some reason, to avoid ambiguity. For example, you can't 
overload a QByteArray with QLatin1String (or Qt6's QByteArrayView or 
QAnyStringView or any such other combination) because it makes calling with a 
character literal ambiguous. But you can if one of them is a weak overload.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel DPG Cloud Engineering



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