Struct Nothing 

pub struct Nothing;

Available on crate feature parsing only.

An empty syntax tree node that consumes no tokens when parsed.

This is useful for attribute macros that want to ensure they are not provided any attribute args.

use proc_macro::TokenStream;
use syn::parse_macro_input;
use syn::parse::Nothing;

#[proc_macro_attribute]
pub fn my_attr(args: TokenStream, input: TokenStream) -> TokenStream {
    parse_macro_input!(args as Nothing);

    /* ... */
}

error: unexpected token
 --> src/main.rs:3:19
  |
3 | #[my_attr(asdf)]
  |           ^^^^

Trait Implementations

impl Clone for Nothing

Available on crate feature clone-impls only.

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Parse for Nothing

fn parse(_input: ParseStream<'_>) -> Result<Self>

impl ToTokens for Nothing

Available on crate feature printing only.

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

Write self to the given TokenStream.

fn to_token_stream(&self) -> TokenStream

Convert self directly into a TokenStream object.

fn into_token_stream(self) -> TokenStream

where Self: Sized,

Convert self directly into a TokenStream object.

impl Copy for Nothing

Available on crate feature clone-impls only.