# Struct proc_macro2::TokenStream

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    pub struct TokenStream { /* private fields */ }

Expand description

An abstract stream of tokens, or more concretely a sequence of token trees.

This type provides interfaces for iterating over token trees and for collecting token trees into one stream.

Token stream is both the input and output of `#[proc_macro]`, `#[proc_macro_attribute]` and `#[proc_macro_derive]` definitions.

## Implementations

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### impl TokenStream

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#### pub fn new() -> Self

Returns an empty `TokenStream` containing no token trees.

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#### pub fn is_empty(&self) -> bool

Checks if this `TokenStream` is empty.

## Trait Implementations

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### impl Clone for TokenStream

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

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 TokenStream

Prints token in a form convenient for debugging.

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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 Default for TokenStream

`TokenStream::default()` returns an empty stream, i.e. this is equivalent with `TokenStream::new()`.

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#### fn default() -> Self

Returns the “default value” for a type. Read more

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### impl Display for TokenStream

Prints the token stream as a string that is supposed to be losslessly convertible back into the same token stream (modulo spans), except for possibly `TokenTree::Group`s with `Delimiter::None` delimiters and negative numeric literals.

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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 Extend<TokenStream> for TokenStream

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#### fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I)

Extends a collection with the contents of an iterator. Read more

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#### fn extend_one(&mut self, item: A)

🔬 This is a nightly-only experimental API. (`extend_one`)

Extends a collection with exactly one element.

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#### fn extend_reserve(&mut self, additional: usize)

🔬 This is a nightly-only experimental API. (`extend_one`)

Reserves capacity in a collection for the given number of additional elements. Read more

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### impl Extend<TokenTree> for TokenStream

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#### fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, streams: I)

Extends a collection with the contents of an iterator. Read more

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#### fn extend_one(&mut self, item: A)

🔬 This is a nightly-only experimental API. (`extend_one`)

Extends a collection with exactly one element.

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#### fn extend_reserve(&mut self, additional: usize)

🔬 This is a nightly-only experimental API. (`extend_one`)

Reserves capacity in a collection for the given number of additional elements. Read more

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### impl From<TokenStream> for TokenStream

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#### fn from(inner: TokenStream) -> TokenStream

Converts to this type from the input type.

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### impl From<TokenStream> for TokenStream

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#### fn from(inner: TokenStream) -> TokenStream

Converts to this type from the input type.

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### impl From<TokenTree> for TokenStream

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#### fn from(token: TokenTree) -> Self

Converts to this type from the input type.

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### impl FromIterator<TokenStream> for TokenStream

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#### fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self

Creates a value from an iterator. Read more

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### impl FromIterator<TokenTree> for TokenStream

Collects a number of token trees into a single stream.

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#### fn from_iter<I: IntoIterator<Item = TokenTree>>(streams: I) -> Self

Creates a value from an iterator. Read more

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### impl FromStr for TokenStream

Attempts to break the string into tokens and parse those tokens into a token stream.

May fail for a number of reasons, for example, if the string contains unbalanced delimiters or characters not existing in the language.

NOTE: Some errors may cause panics instead of returning `LexError`. We reserve the right to change these errors into `LexError`s later.

#### type Err = LexError

The associated error which can be returned from parsing.

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#### fn from_str(src: &str) -> Result<TokenStream, LexError>

Parses a string `s` to return a value of this type. Read more

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### impl IntoIterator for TokenStream

#### type Item = TokenTree

The type of the elements being iterated over.

#### type IntoIter = IntoIter

Which kind of iterator are we turning this into?

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#### fn into_iter(self) -> IntoIterⓘNotable traits for IntoIter `impl Iterator for IntoIter type Item = TokenTree;`

Creates an iterator from a value. Read more

## Auto Trait Implementations

### impl RefUnwindSafe for TokenStream

### impl !Send for TokenStream

### impl !Sync for TokenStream

### impl Unpin for TokenStream

### impl UnwindSafe for TokenStream

## 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.