Struct proc_macro::TokenStream

1.15.0 · source ·
pub struct TokenStream(_);
Expand description

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.

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impl TokenStream

1.29.0 · source

pub fn new() -> TokenStream

Returns an empty TokenStream containing no token trees.

1.29.0 · source

pub fn is_empty(&self) -> bool

Checks if this TokenStream is empty.

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pub fn expand_expr(&self) -> Result<TokenStream, ExpandError>

🔬This is a nightly-only experimental API. (proc_macro_expand #90765)

Parses this TokenStream as an expression and attempts to expand any macros within it. Returns the expanded TokenStream.

Currently only expressions expanding to literals will succeed, although this may be relaxed in the future.

NOTE: In error conditions, expand_expr may leave macros unexpanded, report an error, failing compilation, and/or return an Err(..). The specific behavior for any error condition, and what conditions are considered errors, is unspecified and may change in the future.

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
1.0.0 · source§

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
1.45.0 · source§

impl Default for TokenStream

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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::Groups 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
1.30.0 · source§

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 #72631)
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 #72631)
Reserves capacity in a collection for the given number of additional elements. Read more
1.30.0 · source§

impl Extend<TokenTree> for TokenStream

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fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, trees: 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 #72631)
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 #72631)
Reserves capacity in a collection for the given number of additional elements. Read more
1.29.0 · source§

impl From<TokenTree> for TokenStream

Creates a token stream containing a single token tree.

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fn from(tree: TokenTree) -> TokenStream

Converts to this type from the input type.
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impl FromIterator<TokenStream> for TokenStream

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

Creates a value from an iterator. Read more
1.29.0 · source§

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>>(trees: 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. 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 LexErrors later.

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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
1.29.0 · source§

impl IntoIterator for TokenStream

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type Item = TokenTree

The type of the elements being iterated over.
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type IntoIter = IntoIter

Which kind of iterator are we turning this into?
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fn into_iter(self) -> IntoIter

Creates an iterator from a value. Read more
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impl ToString for TokenStream

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fn to_string(&self) -> String

Converts the given value to a String. Read more
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impl !Send for TokenStream

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impl !Sync for TokenStream

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for Twhere
    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 Twhere
    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 Twhere
    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 Twhere
    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 Twhere
    T: Clone,

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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 Twhere
    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 Twhere
    U: Into<T>,

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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 Twhere
    U: TryFrom<T>,

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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.