pub struct Nothing;
Available on crate feature
parsing
only.Expand description
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§
source§impl PartialEq<Nothing> for Nothing
Available on crate feature extra-traits
only.
impl PartialEq<Nothing> for Nothing
Available on crate feature
extra-traits
only.impl Eq for Nothing
Available on crate feature
extra-traits
only.