Struct ErrorChain 

pub struct ErrorChain { /* private fields */ }

Available on crate feature alloc only.

A diagnostic pairs a GraphError with an optional causal chain.

Both the outer error and every inner cause carry their own WDP code, forming a chain that provides context (what failed) at each level:

[E.ArenaLayout.Builder.026] IR builder allocation failed
  caused by: [E.ArenaLayout.Alloc.026] arena out of memory

Construction

use ascii_dag::errors::{GraphError, ErrorChain};

// Leaf diagnostic (no cause)
let d = ErrorChain::from(GraphError::ArenaOom);
assert_eq!(d.code(), "E.ArenaLayout.Alloc.026");
assert!(d.cause().is_none());

// Chained diagnostic
let d = ErrorChain::from(GraphError::BuilderFailed)
    .caused_by(GraphError::ArenaOom);
assert_eq!(d.code(), "E.ArenaLayout.Builder.026");
assert_eq!(d.cause().unwrap().code(), "E.ArenaLayout.Alloc.026");

Display

Display renders the full chain, indenting each cause level:

use ascii_dag::errors::{GraphError, ErrorChain};

let d = ErrorChain::from(GraphError::BuilderFailed)
    .caused_by(GraphError::ArenaOom);
let msg = d.to_string();
assert!(msg.contains("caused by:"));

Implementations

impl ErrorChain

pub fn new(error: GraphError) -> Self

Create a leaf diagnostic (no cause).

pub fn caused_by(self, cause: GraphError) -> Self

Attach a cause to this diagnostic (builder pattern).

The cause is wrapped in its own ErrorChain with no further inner cause. For deeper chains, use caused_by_chain.

pub fn caused_by_chain(self, cause: ErrorChain) -> Self

Attach an existing ErrorChain as the cause.

pub fn error(&self) -> &GraphError

The GraphError at this level of the chain.

pub fn code(&self) -> &'static str

WDP code of the outermost error.

pub fn hint(&self) -> &'static str

Hint for the outermost error.

pub fn cause(&self) -> Option<&ErrorChain>

The inner cause, if any.

pub fn chain(&self) -> DiagnosticChain<'_>

Iterate over the full chain: self, then cause, then cause’s cause, etc.

Trait Implementations

impl Clone for ErrorChain

fn clone(&self) -> ErrorChain

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ErrorChain

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

Formats the value using the given formatter.

impl Display for ErrorChain

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

Formats the value using the given formatter.

impl Eq for ErrorChain

impl Error for ErrorChain

Available on crate feature std only.

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 From<GraphError> for ErrorChain

fn from(error: GraphError) -> Self

Converts to this type from the input type.

impl PartialEq for ErrorChain

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

Equality operator ==.

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

Inequality operator !=.

impl ProjectedFailure for ErrorChain

fn cause(&self) -> Option<&Self>

The next cause beneath this failure, if any.

impl StructuralPartialEq for ErrorChain