# Struct proc_macro2::Ident

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    pub struct Ident { /* private fields */ }

Expand description

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

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### impl Ident

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

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`.

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

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.

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#### pub fn span(&self) -> Span

Returns the span of this `Ident`.

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

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

## Trait Implementations

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### impl Clone for Ident

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#### fn clone(&self) -> Ident

Returns a copy of the value. Read more

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

Performs copy-assignment from `source`. Read more

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### impl Debug for Ident

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

Formats the value using the given formatter. Read more

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### impl Display for Ident

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

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

Formats the value using the given formatter. Read more

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### impl From<Ident> for TokenTree

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#### fn from(g: Ident) -> TokenTree

Converts to this type from the input type.

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### impl Hash for Ident

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

Feeds this value into the given `Hasher`. Read more

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

Feeds a slice of this type into the given `Hasher`. Read more

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### impl Ord for Ident

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

This method returns an `Ordering` between `self` and `other`. Read more

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

Compares and returns the maximum of two values. Read more

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

Compares and returns the minimum of two values. Read more

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#### fn clamp(self, min: Self, max: Self) -> Self where
Self: PartialOrd<Self>,

Restrict a value to a certain interval. Read more

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### impl PartialEq<Ident> for Ident

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

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

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

This method tests for `!=`.

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### impl<T> PartialEq<T> for Ident where
T: ?Sized + AsRef<str>,

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

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

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

This method tests for `!=`.

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### impl PartialOrd<Ident> for Ident

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

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

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

This method tests less than (for `self` and `other`) and is used by the `<` operator. Read more

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

This method tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more

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

This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more

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

This method tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more

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### impl Eq for Ident

## Auto Trait Implementations

### impl RefUnwindSafe for Ident

### impl !Send for Ident

### impl !Sync for Ident

### impl Unpin for Ident

### impl UnwindSafe for Ident

## Blanket Implementations

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### impl<T> Any for T where
T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more

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### impl<T> Borrow<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

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### impl<T> BorrowMut<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

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### impl<T> From<T> for T

const: unstable · source

#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T where
U: From<T>,

const: unstable · source

#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToOwned for T where
T: Clone,

#### type Owned = T

The resulting type after obtaining ownership.

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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more

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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more

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### impl<T> ToString for T where
T: Display + ?Sized,

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#### default fn to_string(&self) -> String

Converts the given value to a `String`. Read more

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### impl<T, U> TryFrom<U> for T where
U: Into<T>,

#### type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.

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### impl<T, U> TryInto<U> for T where
U: TryFrom<T>,

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.