Struct ClassificationMarker 

pub struct ClassificationMarker { /* private fields */ }

A transparent classification marker with an optional owned source and no diagnostic of its own.

Unlike Message, markers only supply classification metadata, never a visible diagnostic. Use Message to combine a message, class, and scalar values in one causal error; use a marker to classify an existing concrete error without changing its diagnostic or recovery payload. Self::with_source() adds a classification to an existing error while preserving its concrete type and diagnostic. The associated constants, such as Self::NOT_FOUND, are owned class-only markers. A custom error can return Some(const { &ClassificationMarker::NOT_FOUND }) from its source() implementation without defining a static. Self::with_class() creates an owned class-only marker, including for Class::Io with a specific I/O kind.

Diagnostic iterators, downcasts, cause selection, and exception/test reports skip all markers, retaining their real descendants. crate::classify() still inspects markers. Raw standard-error sources can still expose markers. A report with only class-only markers falls back to displaying the root classification. If cause selection cannot choose a unique real descendant, it can likewise fall back to the stored marker root. Preserve real std::io::Error sources: the marker itself has no I/O origin for crate::types::Classification::io_kind().

Implementations

impl ClassificationMarker

pub const VALIDATION: Self

A hidden marker for invalid input.

pub const CORRUPTION: Self

A hidden marker for malformed or internally inconsistent data.

pub const NOT_FOUND: Self

A hidden marker for a requested resource that does not exist.

pub const RETRYABLE: Self

A hidden marker for an operation which may succeed when retried.

pub const ALLOCATION_LIMIT: Self

A hidden marker for an application-configured allocation limit being exceeded.

pub const ALLOCATION_FAILURE: Self

A hidden marker for an unrepresentable allocation size or memory that could not be reserved.

pub fn with_source( class: Class, source: impl Error + Send + Sync + 'static, ) -> Self

Add class to source, preserving its concrete type and diagnostic without a visible wrapper.

pub const fn with_class(class: Class) -> Self

Create a hidden metadata leaf, suitable for a custom error’s static source. Prefer the associated constants, such as Self::NOT_FOUND, for fixed classifications.

pub fn class(&self) -> Class

Return the classification supplied by this marker.

Trait Implementations

impl Debug for ClassificationMarker

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

Formats the value using the given formatter.

impl Display for ClassificationMarker

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

Formats the value using the given formatter.

impl Error for ClassificationMarker

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.