Struct syn::parse::Nothing

pub struct Nothing;

This is supported 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 Parse for Nothing

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