Struct ParseFail 

pub struct ParseFail {
    pub input_span: (usize, usize),
    pub expected: String,
    pub parser_span: Option<(u32, u32)>,
    pub partial: Option<GcRef>,
}

A single parse mismatch (§7.11), carrying structured detail for the crash debugger and the noninteractive fallback.

Constructed by the parser interpreter at each failure site via ParseFail::here; the ParseDetail slot keeps the most specific one.

Fields

input_span: (usize, usize)

[start, end) byte offsets into the input buffer where the mismatch occurred. end may equal start for a zero-width expectation (e.g. “expected a digit, found end-of-input”).

expected: String

What the parser expected, as a short human description ("int", "literal ':'", "section header", "6 sections for `shapes`", …). A String rather than a &'static str precisely so a description can name the thing that came up short.

parser_span: Option<(u32, u32)>

The source span of the failing parser expression (byte offsets into the program source). None when no span was threaded (an internal-only plan node); the renderer falls back to <unknown parser>.

partial: Option<GcRef>

The best-effort partial root value built before the failure (the deepest successfully-assembled sub-value), or None when no partial value was available. The collector retains it because the runtime roots ParseDetail (see crate::ParseDetail).

Implementations

impl ParseFail

pub fn here(offset: usize, expected: impl Into<String>) -> Self

Construct a failure at offset (zero-width) expecting expected. Convenience for the common “found X, expected Y at this point” case.

pub fn at(offset: usize, len: usize, expected: impl Into<String>) -> Self

With a width: the mismatch span is [offset, offset + len).

pub fn with_parser_span(self, span: Option<(u32, u32)>) -> Self

Attach the source span of the failing parser expression.

pub fn with_partial(self, partial: Option<GcRef>) -> Self

Attach the best-effort partial root value.

Trait Implementations

impl Clone for ParseFail

fn clone(&self) -> ParseFail

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ParseFail

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

Formats the value using the given formatter.