QVectorND: make some constructors explicit

QVector2D has implicit conversions towards QVector3D/4D, and
QVector3D has an implicit conversion towards QVector4D. Although
in principle this is fine because it's not a data loss, it's still
sketchy; for instance, it allows mixed operations to compile:

  vector2d + vector3d;
  vector4d - vector3d;
  vector3d * vector4d; // !

(Random observation: the conversion from QPoint(F) to QVectorND are
actually already marked as explicit.)

This is a leftover not done for Qt 6.0. I am not making these opt-out:
having an implicit conversion here is outright *dangerous*, and any usage
that fails to compile needs to be inspected to make sure it was the
intended behavior.

[ChangeLog][Potentially Source-Incompatible Changes] The
QVector2D/3D/4D converting constructors from another QVectorND
now explicit. This was done to prevent a category of bugs resulting
from operations accidentally mixing QVectorND objects.

Fixes: QTBUG-90327
Change-Id: Ifcd873f6a0d3fc10b9e68c935fe1f69f86a2340b
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

0 files changed, 0 insertions, 0 deletions