There are also currently the unstable rustc_layout_scalar_valid_range_start and rustc_layout_scalar_valid_range_end attributes (which are used in the definition

There are also currently the unstable rustc_layout_scalar_valid_range_start and rustc_layout_scalar_valid_range_end attributes (which are used in the definition of NonNull, etc.) which could be used for some bit patterns. Also aspirations to use pattern types for this sort of thing: https://github.com/rust-lang/rust/issues/135996 https://github.com/rust-lang/rust/issues/135996