I feel like there should be a "sign-queer" integer. It's range is the intersection of unsigned and signed integers, in other words the high bit must be unset. Wrapping around on either end is illegal and should be diagnosed in debug builds. In production builds it may either be silently treated as an unsigned integer or generate a diagnostic.
Implicitly casting to either signed or unsigned integer is allowed and does not generate a warning.
That's the behavior you get in Zig, if you declare a variable of type `u31`: an unsigned 31-bit integer that's implicitly convertible to `u32` or `i32`.
Also in Zig overflow is illegal for both signed and unsigned integers, and guaranteed to be detected when building in Safe mode (but not in Fast mode). There is a separate set of operators for wrapping arithmetic.
Implicitly casting to either signed or unsigned integer is allowed and does not generate a warning.