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

    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.

## Methods

###

`impl TokenStream`

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####

`pub fn new() -> TokenStream`

1.29.0
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Returns an empty `TokenStream` containing no token trees.

####

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

1.29.0
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Checks if this `TokenStream` is empty.

## Trait Implementations

###

`impl IntoIterator for TokenStream`

1.29.0
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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`

1.29.0
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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.

###

`impl FromIterator<TokenTree> for TokenStream`

1.29.0
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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.

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

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Creates a value from an iterator. Read more

###

`impl Extend<TokenTree> for TokenStream`

1.30.0
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####

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

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

###

`impl Extend<TokenStream> for TokenStream`

1.30.0
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####

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

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

## Blanket Implementations

###

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

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#### `type Owned = T`

####

`fn to_owned(&self) -> T`

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

####

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

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🔬 This is a nightly-only experimental API. (`toowned_clone_into` #41263)

recently added

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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`fn to_string(&self) -> String`

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

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

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####

`fn into(self) -> U`

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Performs the conversion.

###

`impl<T> From for T`

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####

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

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Performs the conversion.

###

`impl<I> IntoIterator for I where I: Iterator,`

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#### `type Item = <I as Iterator>::Item`

The type of the elements being iterated over.

#### `type IntoIter = I`

Which kind of iterator are we turning this into?

####

`fn into_iter(self) -> I`

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Creates an iterator from a value. Read more

###

`impl<T, U> TryFrom for T where T: From<U>,`

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#### `type Error = !`

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

####

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

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🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

###

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

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####

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

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Immutably borrows from an owned value. Read more

###

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

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####

`fn get_type_id(&self) -> TypeId`

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🔬 This is a nightly-only experimental API. (`get_type_id` #27745)

this method will likely be replaced by an associated static

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

###

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

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

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

####

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

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🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

###

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

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####

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

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Mutably borrows from an owned value. Read more

###

`impl<E> SpecializationError for E`

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####

`fn not_found<S, T>(trait_name: &'static str, method_name: &'static str) -> E where T: ?Sized,`

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🔬 This is a nightly-only experimental API. (`rustc_private` #27812)

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?

Create an error for a missing method specialization. Defaults to panicking with type, trait & method names. `S` is the encoder/decoder state type, `T` is the type being encoded/decoded, and the arguments are the names of the trait and method that should've been overridden. Read more

###

`impl<T> Erased for T`

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`impl<T> Send for T where T: ?Sized,`

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`impl<T> Sync for T where T: ?Sized,`

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###

`impl<T> Erased for T`

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