Struct ParseError 

pub struct ParseError { /* private fields */ }

A parse error carrying the original proc_macro2::Span of the offending token or expression start, plus an optional end span for range errors.

Used as the return type of all parser methods. Not Send + Sync because proc_macro2::Span wraps a compiler-internal handle that is only valid on the proc-macro thread. Convert to [CELError] via From when the error must cross thread boundaries or be stored for async reporting.

Examples

See Self::new, Self::new_range and Self::with_cause.

Implementations

impl ParseError

pub fn with_cause(self, cause: impl Error + 'static) -> ParseError

Retains an immutable frontend cause without replacing its concrete error type.

Cloning the parse error shares this cause. Conversion to [CELError] retains only the message and primary span for thread-safe reporting.

Examples

use std::error::Error;
let error = cel_parser::ParseError::new("frontend", proc_macro2::Span::call_site())
    .with_cause(std::io::Error::other("original"));
assert!(error.source().unwrap().is::<std::io::Error>());

pub fn new(message: impl Into<String>, span: Span) -> ParseError

Creates a new parse error with the given message and token span.

• Complexity: O(m) time and space for m borrowed message bytes; transferring a String is O(1). Other message types contribute their Into<String> conversion cost.

Examples

use proc_macro2::Span;
use cel_parser::ParseError;

let e = ParseError::new("unexpected token", Span::call_site());
assert_eq!(e.message(), "unexpected token");

pub fn new_range( message: impl Into<String>, start: Span, end: Span, ) -> ParseError

Creates a parse error spanning a sub-expression from start to end.

Use this for op-lookup failures where the error implicates a full sub-expression rather than a single token. At runtime the two spans are merged into a contiguous underline; at compile time two separate compile_error!() diagnostics are emitted.

• Complexity: Matches the message conversion in Self::new.

Examples

use proc_macro2::Span;
use cel_parser::ParseError;

let start = Span::call_site();
let end = Span::call_site();
let e = ParseError::new_range("type mismatch", start, end);
assert_eq!(e.message(), "type mismatch");
assert!(e.end_span().is_some());

pub fn message(&self) -> &str

Returns the error message.

Examples

See Self::new.

pub fn span(&self) -> Span

Returns the proc_macro2::Span of the offending token.

Use this span with quote_spanned! in proc-macro code to attach the compile_error! to the exact source location.

Examples

use cel_parser::ParseError;
let error = ParseError::new("bad name", proc_macro2::Span::call_site());
assert_eq!(error.span().start().column, 0);

pub fn end_span(&self) -> Option<Span>

Returns the end span of this error, or None for single-point errors.

Some for errors created with new_range; None for errors created with new.

Examples

See Self::new_range.

pub fn with_secondary(self, secondary: Vec<SpanLabel>) -> ParseError

Attaches secondary labelled spans, rendered as extra carets alongside the primary.

• Complexity: O(k) to release k previously attached labels; transfers the new vector.

Examples

use proc_macro2::Span;
use cel_parser::{ParseError, SourceSpan, SpanLabel};

let e = ParseError::new("bad", Span::call_site()).with_secondary(vec![SpanLabel {
    span: SourceSpan::new(1, 4, 1, 7),
    label: "also here".into(),
}]);
assert_eq!(e.message(), "bad");

pub fn secondary(&self) -> &[SpanLabel]

Returns the secondary labelled spans attached to this error.

Examples

use cel_parser::{ParseError, SourceSpan, SpanLabel};
use proc_macro2::Span;

let e = ParseError::new("bad", Span::call_site()).with_secondary(vec![SpanLabel {
    span: SourceSpan::new(1, 0, 1, 3),
    label: "related".into(),
}]);
assert_eq!(e.secondary().len(), 1);

pub fn from_lex_error(source: &str, err: LexError) -> ParseError

Converts a lex failure (e.g. from proc_macro2::TokenStream::from_str) into a ParseError with a message describing the likely cause.

proc_macro2::LexError’s Display is the same generic string (“cannot parse string into token stream”) regardless of cause, but its span reliably points at the offending character. This inspects that character in source to report why lexing failed — unclosed/unexpected delimiter, unterminated string or character literal, unterminated block comment, or another invalid character — falling back to err’s own message only when the span doesn’t resolve to a character in source (e.g. it points past the end).

• Complexity: O(s) inspection for s source bytes, plus lexer error display when needed; O(s) auxiliary/output space in delimiter classification.

Examples

use cel_parser::ParseError;
use proc_macro2::TokenStream;
use std::str::FromStr;

let source = "(1 + 2";
let lex_err = TokenStream::from_str(source).unwrap_err();
let err = ParseError::from_lex_error(source, lex_err);
assert_eq!(err.message(), "unclosed delimiter `(`: expected a matching `)`");

pub fn format_rustc_style( &self, source_code: &str, filename: &str, start_line: u32, renderer: &Renderer, ) -> String

Formats this error in rustc diagnostic style with source context.

Identical contract to [CELError::format_rustc_style] when no secondary spans are attached; prefer calling this directly on a ParseError rather than converting to CELError first when you have the source text at hand. When secondaries have been added via with_secondary, renders a multi-span diagnostic (the primary span plus one context caret per secondary) via [format_multi_span].

• Complexity: O(k * s + l) annotation work for k total labels, s source bytes and l secondary-label bytes, plus renderer layout; O(k + l + s + b) auxiliary/output space for b output bytes.

Examples

use annotate_snippets::Renderer;
use cel_parser::CELParser;
use cel_parser::OpLookup;

let line = line!() + 1;
let source = "10 + 20 30";
let mut parser = CELParser::new(OpLookup::new());
if let Err(e) = parser.parse_str(source) {
    println!("{}", e.format_rustc_style(source, file!(), line, &Renderer::plain()));
}

Trait Implementations

impl Clone for ParseError

fn clone(&self) -> ParseError

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ParseError

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

Formats the value using the given formatter.

impl Display for ParseError

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

Writes m message bytes in O(m) time without allocating an intermediate string.

impl Error for ParseError

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

Borrows the retained original frontend cause, if present.

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.