[Development] QVariant::operator< deprecation fallout

Giuseppe D'Angelo giuseppe.dangelo at kdab.com
Mon Nov 23 15:47:23 CET 2020


On 23/11/2020 08:48, Fabian Kosmale wrote:
> I think we should at least_somehow_  deprecate operator<; but I'm not sure if it should be a special deprecation macro, or a special one. 

I'm guessing you meant generic / special. I'm more keen on keeping 
everything deprecated, but with a special macro. (Or maybe just bump the 
deprecation version to 6.0 instead of 5.15?)

A deprecation without replacement in the same Qt version is a dead end 
for a user; and the last thing we want is for users to switch _OFF_ 
deprecation warnings because they depend on stuff they can't fix.

> Regarding point 4: Unfortunately, it's not that easy: If userType is actually a built-in type, then QMetaType::hasRegisteredComparators returns false, and QMetaType compare will not work. I'm afraid that in this case you would actually have to call the deprecated operator< [1]; unless we provide a replacement functionality in 5.15.3.

Ouch, right, this is the sort of things that really call for a helper 
function with the right semantics™ to be added. But if we can't keep 
that function compatible with Qt 6 anyhow, then we also burn the 
"compare" name.

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 84 08 53, http://www.kdab.com
KDAB - The Qt, C++ and OpenGL Experts

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