Since we expect the result of `rcp` and `safe_rcp` to always be in the range of [0, 1], it doesn't make sense to allow passing in integer types without casting them, as this has a high possibility of introducing unwanted behavior by only returning either 0 or 1. To prevent this, this commit adds a static assert on the type. Pull Request: https://projects.blender.org/blender/blender/pulls/141567