Struct UnknownDiscriminant 

#[non_exhaustive]
pub struct UnknownDiscriminant {
    pub value: u128,
    pub type_name: &'static str,
}

The error returned by the TryFrom<uN> impl that #[derive(BitEnum)] generates for a primitive-width enum without a #[catch_all] variant (width u8/u16/u32/u64/u128): the value matched no known discriminant.

A catch-all enum is total, so its primitive→enum conversion is an infallible From and never produces this. This mirrors num_enum’s TryFromPrimitiveError. Decoding through the codec / Bits::from_bits is unaffected — that path stays permissive (dual-use); this is only for the caller who opts into a checked conversion.

Examples

#[derive(bnb::BitEnum, Clone, Copy, Debug, PartialEq, Eq)]
#[bit_enum(u8, closed)]
#[repr(u8)]
enum Direction { Request = 1, Reply = 2 }

let err = Direction::try_from(9u8).unwrap_err(); // no variant for 9
assert_eq!(err.value, 9);
assert_eq!(err.type_name, "Direction");
assert_eq!(err.to_string(), "Direction has no variant for discriminant 9");

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

value: u128

The unrecognized value.

type_name: &'static str

The name of the enum that rejected it.

Implementations

impl UnknownDiscriminant

pub const fn new(value: u128, type_name: &'static str) -> Self

Builds the error for a value that matched no discriminant of the enum named type_name. Called by #[derive(BitEnum)]-generated TryFrom impls.

Trait Implementations

impl Clone for UnknownDiscriminant

fn clone(&self) -> UnknownDiscriminant

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for UnknownDiscriminant

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for UnknownDiscriminant

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for UnknownDiscriminant

impl Error for UnknownDiscriminant

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl PartialEq for UnknownDiscriminant

fn eq(&self, other: &UnknownDiscriminant) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for UnknownDiscriminant