qSwap() is our wrapper around
using std::swap;
swap(lhs, rhs);
it needn't and shouldn't be overloaded.
ADL swap() should be, though, so qSwap(), std::ranges::swap() and all
the other adl_swap()s out there all find the optimized version.
Qt 5.15 has it correct, Qt 6 wrong. Fix it.
Can't pick to 6.2 because, while backwards-source-compatible, because
the generic qSwap() template provides the name for both qualified and
unqualified calls, it's not forwards-source-compatible: A new user of
ADL swap
// compile error w/o `using std::swap`, pessimization otherwise:
swap(dp1, dp2);
would break or performance-regress when going back to an older
version.
Pick-to: 6.3
Change-Id: I725949a4aa9ae438a182b4b7552ff2dced767e2f
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
e6d4967f0b