Struct Ident 

pub struct Ident { /* private fields */ }

A word of Rust code, which may be a keyword or legal variable name.

An identifier consists of at least one Unicode code point, the first of which has the XID_Start property and the rest of which have the XID_Continue property.

• The empty string is not an identifier. Use Option<Ident>.
• A lifetime is not an identifier. Use syn::Lifetime instead.

An identifier constructed with Ident::new is permitted to be a Rust keyword, though parsing one through its Parse implementation rejects Rust keywords. Use input.call(Ident::parse_any) when parsing to match the behaviour of Ident::new.

Examples

A new ident can be created from a string using the Ident::new function. A span must be provided explicitly which governs the name resolution behavior of the resulting identifier.

use proc_macro2::{Ident, Span};

fn main() {
    let call_ident = Ident::new("calligraphy", Span::call_site());

    println!("{}", call_ident);
}

An ident can be interpolated into a token stream using the quote! macro.

use proc_macro2::{Ident, Span};
use quote::quote;

fn main() {
    let ident = Ident::new("demo", Span::call_site());

    // Create a variable binding whose name is this ident.
    let expanded = quote! { let #ident = 10; };

    // Create a variable binding with a slightly different name.
    let temp_ident = Ident::new(&format!("new_{}", ident), Span::call_site());
    let expanded = quote! { let #temp_ident = 10; };
}

A string representation of the ident is available through the to_string() method.

// Examine the ident as a string.
let ident_string = ident.to_string();
if ident_string.len() > 60 {
    println!("Very long identifier: {}", ident_string)
}

Implementations

impl Ident

pub fn new(string: &str, span: Span) -> Ident

Creates a new Ident with the given string as well as the specified span.

The string argument must be a valid identifier permitted by the language, otherwise the function will panic.

Note that span, currently in rustc, configures the hygiene information for this identifier.

As of this time Span::call_site() explicitly opts-in to “call-site” hygiene meaning that identifiers created with this span will be resolved as if they were written directly at the location of the macro call, and other code at the macro call site will be able to refer to them as well.

Later spans like Span::def_site() will allow to opt-in to “definition-site” hygiene meaning that identifiers created with this span will be resolved at the location of the macro definition and other code at the macro call site will not be able to refer to them.

Due to the current importance of hygiene this constructor, unlike other tokens, requires a Span to be specified at construction.

Panics

Panics if the input string is neither a keyword nor a legal variable name. If you are not sure whether the string contains an identifier and need to handle an error case, use syn::parse_str::<Ident> rather than Ident::new.

pub fn new_raw(string: &str, span: Span) -> Ident

Same as Ident::new, but creates a raw identifier (r#ident). The string argument must be a valid identifier permitted by the language (including keywords, e.g. fn). Keywords which are usable in path segments (e.g. self, super) are not supported, and will cause a panic.

pub fn span(&self) -> Span

Returns the span of this Ident.

pub fn set_span(&mut self, span: Span)

Configures the span of this Ident, possibly changing its hygiene context.

Trait Implementations

impl AsRef<Ident> for KChild

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KConst

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KCrate

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KDefault

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KDenyUnknownFields

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KDoc

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KEnum

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KFacet

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KFlatten

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KIn

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KInvariants

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KMut

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KOpaque

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KPub

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KRename

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KRenameAll

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KRepr

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KSensitive

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KSkipSerializing

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KSkipSerializingIf

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KStruct

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KTransparent

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KTypeTag

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<Ident> for KWhere

fn as_ref(&self) -> &Ident

Converts this type into a shared reference of the (usually inferred) input type.

impl Clone for Ident

fn clone(&self) -> Ident

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Ident

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

Formats the value using the given formatter.

impl Display for Ident

Prints the identifier as a string that should be losslessly convertible back into the same identifier.

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

Formats the value using the given formatter.

impl From<Ident> for TokenTree

fn from(g: Ident) -> TokenTree

Converts to this type from the input type.

impl Hash for Ident

fn hash<H>(&self, hasher: &mut H)

where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Ident

fn cmp(&self, other: &Ident) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl Parser for Ident

fn parser( tokens: &mut ShadowCountedIter<'_, <TokenStream as IntoIterator>::IntoIter>, ) -> Result<Ident, Error>

The actual parsing function that must be implemented. This mutates the tokens iterator directly. It should not be called from user code except for implementing parsers itself and then only when the rules below are followed.

impl<T> PartialEq<T> for Ident

where T: AsRef<str> + ?Sized,

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq for Ident

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Ident

fn partial_cmp(&self, other: &Ident) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl ToTokens for Ident

fn to_tokens(&self, tokens: &mut TokenStream)

Write &self to the given TokenStream.

fn to_token_iter( &self, ) -> ShadowCountedIter<'_, <TokenStream as IntoIterator>::IntoIter>

Convert &self into a TokenIter object.

fn into_token_iter<'a>( self, ) -> ShadowCountedIter<'a, <TokenStream as IntoIterator>::IntoIter>

where Self: Sized,

Convert self into a TokenIter object.

fn to_token_stream(&self) -> TokenStream

Convert &self into a TokenStream object.

fn into_token_stream(self) -> TokenStream

where Self: Sized,

Convert self into a TokenStream object.

fn tokens_to_string(&self) -> String

Convert &self into a String object. This is mostly used in the test suite to compare the outputs. When the input is a &str then this parses it and returns a normalized String.

impl Eq for Ident