Trait IdentExt

pub trait IdentExt: Sized + Sealed {
    const peek_any: PeekFn = private::PeekFn;

    // Required methods
    fn parse_any(input: ParseStream<'_>) -> Result<Self>;
    fn unraw(&self) -> Ident;
}

Available on crate feature parsing only.

Additional methods for Ident not provided by proc-macro2 or libproc_macro.

This trait is sealed and cannot be implemented for types outside of Syn. It is implemented only for proc_macro2::Ident.

Provided Associated Constants

const peek_any: PeekFn = private::PeekFn

Peeks any identifier including keywords. Usage: input.peek(Ident::peek_any)

This is different from input.peek(Ident) which only returns true in the case of an ident which is not a Rust keyword.

Required Methods

fn parse_any(input: ParseStream<'_>) -> Result<Self>

Parses any identifier including keywords.

This is useful when parsing macro input which allows Rust keywords as identifiers.

Example

use syn::{Error, Ident, Result, Token};
use syn::ext::IdentExt;
use syn::parse::ParseStream;

mod kw {
    syn::custom_keyword!(name);
}

// Parses input that looks like `name = NAME` where `NAME` can be
// any identifier.
//
// Examples:
//
//     name = anything
//     name = impl
fn parse_dsl(input: ParseStream) -> Result<Ident> {
    input.parse::<kw::name>()?;
    input.parse::<Token![=]>()?;
    let name = input.call(Ident::parse_any)?;
    Ok(name)
}

fn unraw(&self) -> Ident

Strips the raw marker r#, if any, from the beginning of an ident.

• unraw(x) = x
• unraw(move) = move
• unraw(r#move) = move

Example

In the case of interop with other languages like Python that have a different set of keywords than Rust, we might come across macro input that involves raw identifiers to refer to ordinary variables in the other language with a name that happens to be a Rust keyword.

The function below appends an identifier from the caller’s input onto a fixed prefix. Without using unraw(), this would tend to produce invalid identifiers like __pyo3_get_r#move.

use proc_macro2::Span;
use syn::Ident;
use syn::ext::IdentExt;

fn ident_for_getter(variable: &Ident) -> Ident {
    let getter = format!("__pyo3_get_{}", variable.unraw());
    Ident::new(&getter, Span::call_site())
}

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl IdentExt for Ident