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#![feature(proc_macro_quote)]
extern crate proc_macro;
use proc_macro::*;
#[proc_macro]
pub fn proc_macro_rules(input: TokenStream) -> TokenStream {
if input.is_empty() {
let id = |s| TokenTree::from(Ident::new(s, Span::mixed_site()));
let item_def = id("ItemDef");
let local_def = id("local_def");
let item_use = id("ItemUse");
let local_use = id("local_use");
let mut single_quote = Punct::new('\'', Spacing::Joint);
single_quote.set_span(Span::mixed_site());
let label_use: TokenStream = [
TokenTree::from(single_quote),
id("label_use"),
].iter().cloned().collect();
quote!(
struct $item_def;
let $local_def = 0;
$item_use; // OK
$local_use; // ERROR
break $label_use; // ERROR
)
} else {
let mut dollar_crate = input.into_iter().next().unwrap();
dollar_crate.set_span(Span::mixed_site());
quote!(
type A = $dollar_crate::ItemUse;
)
}
}
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