Struct syn::parse::Error

[+] Show declaration

pub struct Error { /* fields omitted */ }

[−] Expand description

Error returned when a Syn parser cannot parse the input tokens.

Refer to the module documentation for details about parsing in Syn.

This type is available if Syn is built with the "parsing" feature.

Methods

impl Error

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pub fn new<T: Display>(span: Span, message: T) -> Self

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Usually the ParseStream::error method will be used instead, which automatically uses the correct span from the current position of the parse stream.

Use Error::new when the error needs to be triggered on some span other than where the parse stream is currently positioned.

Example

#[macro_use]
extern crate syn;

use syn::{Ident, LitStr};
use syn::parse::{Error, ParseStream, Result};

// Parses input that looks like `name = "string"` where the key must be
// the identifier `name` and the value may be any string literal.
// Returns the string literal.
fn parse_name(input: ParseStream) -> Result<LitStr> {
    let name_token: Ident = input.parse()?;
    if name_token != "name" {
        // Trigger an error not on the current position of the stream,
        // but on the position of the unexpected identifier.
        return Err(Error::new(name_token.span(), "expected `name`"));
    }
    input.parse::<Token![=]>()?;
    let s: LitStr = input.parse()?;
    Ok(s)
}

pub fn span(&self) -> Span

pub fn to_compile_error(&self) -> TokenStream

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Render the error as an invocation of compile_error!.

The parse_macro_input! macro provides a convenient way to invoke this method correctly in a procedural macro.

Trait Implementations

impl Debug for Error

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

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Formats the value using the given formatter.

impl Clone for Error

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fn clone(&self) -> Error

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Returns a copy of the value.

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

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Performs copy-assignment from source.

impl Display for Error

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fn fmt(&self, formatter: &mut Formatter) -> Result

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Formats the value using the given formatter.

impl Error for Error

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fn description(&self) -> &str

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This method is soft-deprecated.

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

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The lower-level cause of this error, if any.

impl From<LexError> for Error

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fn from(err: LexError) -> Self

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Performs the conversion.