pub struct Nothing;
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
impl Eq for Nothing
Auto Trait Implementations
impl RefUnwindSafe for Nothing
impl Send for Nothing
impl Sync for Nothing
impl Unpin for Nothing
impl UnwindSafe for Nothing
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more