Struct syn::Attribute

pub struct Attribute {
    pub pound_token: Pound,
    pub style: AttrStyle,
    pub bracket_token: Bracket,
    pub path: Path,
    pub tts: TokenStream,
    pub is_sugared_doc: bool,
}

An attribute like #[repr(transparent)].

This type is available if Syn is built with the "derive" or "full" feature.

Syntax

Rust has six types of attributes.

• Outer attributes like #[repr(transparent)]. These appear outside or in front of the item they describe.
• Inner attributes like #![feature(proc_macro)]. These appear inside of the item they describe, usually a module.
• Outer doc comments like /// # Example.
• Inner doc comments like //! Please file an issue.
• Outer block comments /** # Example */.
• Inner block comments /*! Please file an issue */.

The style field of type AttrStyle distinguishes whether an attribute is outer or inner. Doc comments and block comments are promoted to attributes that have is_sugared_doc set to true, as this is how they are processed by the compiler and by macro_rules! macros.

The path field gives the possibly colon-delimited path against which the attribute is resolved. It is equal to "doc" for desugared doc comments. The tts field contains the rest of the attribute body as tokens.

#[derive(Copy)]      #[crate::precondition x < 5]
  ^^^^^^~~~~~~         ^^^^^^^^^^^^^^^^^^^ ~~~~~
   path  tts                   path         tts

Use the interpret_meta method to try parsing the tokens of an attribute into the structured representation that is used by convention across most Rust libraries.

Fields

pound_token: Pound

style: AttrStyle

bracket_token: Bracket

path: Path

tts: TokenStream

is_sugared_doc: bool

Methods

impl Attribute

pub fn parse_inner(i: Cursor) -> PResult<Self>

pub fn parse_outer(i: Cursor) -> PResult<Self>

impl Attribute

pub fn interpret_meta(&self) -> Option<Meta>

Parses the tokens after the path as a Meta if possible.

Trait Implementations

impl Clone for Attribute

fn clone(&self) -> Attribute

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Eq for Attribute

impl PartialEq<Attribute> for Attribute

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

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

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

This method tests for !=.

impl Debug for Attribute

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

Formats the value using the given formatter.

impl Hash for Attribute

fn hash<H>(&self, state: &mut H) where     H: Hasher,

Feeds this value into the given [Hasher].

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

Feeds a slice of this type into the given [Hasher].

impl ToTokens for Attribute

fn to_tokens(&self, tokens: &mut Tokens)

Write self to the given Tokens.

fn into_tokens(self) -> Tokens

Convert self directly into a Tokens object.