This means we'll get warnings whenever a floating point value looses
precision, e.g. gets implicitly casted to an integer. It also warns when
implicitly casting double's to float's, which arguably is less of a
problem, but there are no warning for just float/double to int.

This would have caught
https://gitlab.gnome.org/GNOME/mutter/-/issues/3530.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3822>