# Struct proc_macro::TokenStream 1.15.0[−][src]

    pub struct TokenStream(_);

The main type provided by this crate, representing an abstract stream of tokens, or, more specifically, a sequence of token trees. The type provide interfaces for iterating over those token trees and, conversely, collecting a number of token trees into one stream.

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

The API of this type is intentionally bare-bones, but it'll be expanded over time!

## Methods

###

`impl TokenStream`

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####

`pub fn new() -> TokenStream`

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🔬 This is a nightly-only experimental API. (`proc_macro` #38356)

Returns an empty `TokenStream` containing no token trees.

####

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

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🔬 This is a nightly-only experimental API. (`proc_macro` #38356)

Checks if this `TokenStream` is empty.

## Trait Implementations

###

`impl IntoIterator for TokenStream`

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#### `type Item = TokenTree`

The type of the elements being iterated over.

#### `type IntoIter = IntoIter`

Which kind of iterator are we turning this into?

####
ⓘImportant traits for IntoIter

### Important traits for IntoIter

`impl Iterator for IntoIter type Item = TokenTree;`

`fn into_iter(self) -> IntoIter`

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Creates an iterator from a value. Read more

###

`impl Clone for TokenStream`

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####

`fn clone(&self) -> TokenStream`

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Returns a copy of the value. Read more

####

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

1.0.0
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Performs copy-assignment from `source`. Read more

###

`impl !Send for TokenStream`

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###

`impl !Sync for TokenStream`

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###

`impl FromStr for TokenStream`

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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. All tokens in the parsed stream get `Span::call_site()` spans.

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.

####

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

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

###

`impl Display for TokenStream`

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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.

####

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

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Formats the value using the given formatter. Read more

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`impl Debug for TokenStream`

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Prints token in a form convenient for debugging.

####

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

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Formats the value using the given formatter. Read more

###

`impl From<TokenTree> for TokenStream`

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Creates a token stream containing a single token tree.

####

`fn from(tree: TokenTree) -> TokenStream`

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Performs the conversion.

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`impl FromIterator<TokenTree> for TokenStream`

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Collects a number of token trees into a single stream.

####

`fn from_iter<I: IntoIterator<Item = TokenTree>>(trees: I) -> Self`

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Creates a value from an iterator. Read more

###

`impl FromIterator<TokenStream> for TokenStream`

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A "flattening" operation on token streams, collects token trees from multiple token streams into a single stream.

####

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

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Creates a value from an iterator. Read more

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