Byte::from_f64/from_f32 let +inf past the size >= 0.0 guard and then called the no_std ceil helpers, which used Decimal::from_f64(v).unwrap(). Decimal conversion returns None for non-finite values, so this panicked in no_std builds while std returned None. Fall back to the input value for non-finite input so no_std matches std and the documented None contract is upheld.