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#![feature(proc_macro_quote)]
extern crate proc_macro;
use proc_macro::*;
#[proc_macro]
pub fn proc_macro_item(input: TokenStream) -> TokenStream {
input
}
#[proc_macro]
pub fn proc_macro_rules(_input: TokenStream) -> TokenStream {
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();
let dollar_crate = id("$crate");
quote!(
use $dollar_crate::proc_macro_item as _; // OK
type A = $dollar_crate::ItemUse; // ERROR
struct $item_def;
let $local_def = 0;
$item_use; // OK
$local_use; // ERROR
break $label_use; // ERROR
)
}
#[proc_macro]
pub fn with_crate(input: TokenStream) -> TokenStream {
let mut input = input.into_iter();
let TokenTree::Ident(mut krate) = input.next().unwrap() else { panic!("missing $crate") };
let TokenTree::Ident(span) = input.next().unwrap() else { panic!("missing span") };
let TokenTree::Ident(ident) = input.next().unwrap() else { panic!("missing ident") };
match (krate.to_string().as_str(), span.to_string().as_str()) {
("$crate", "input") => {},
(_, "input") => krate = Ident::new("$crate", krate.span()),
("$crate", "mixed") => krate.set_span(Span::mixed_site()),
(_, "mixed") => krate = Ident::new("$crate", Span::mixed_site()),
("$crate", "call") => krate.set_span(Span::call_site()),
(_, "call") => krate = Ident::new("$crate", Span::call_site()),
(_, x) => panic!("bad span {}", x),
}
quote!(use $krate::$ident as _;)
}
#[proc_macro]
pub fn declare_macro(input: TokenStream) -> TokenStream {
let mut input = input.into_iter();
let TokenTree::Ident(mut krate) = input.next().unwrap() else { panic!("missing $crate") };
let TokenTree::Ident(span) = input.next().unwrap() else { panic!("missing span") };
let TokenTree::Ident(ident) = input.next().unwrap() else { panic!("missing ident") };
match (krate.to_string().as_str(), span.to_string().as_str()) {
("$crate", "input") => {},
(_, "input") => krate = Ident::new("$crate", krate.span()),
("$crate", "mixed") => krate.set_span(Span::mixed_site()),
(_, "mixed") => krate = Ident::new("$crate", Span::mixed_site()),
("$crate", "call") => krate.set_span(Span::call_site()),
(_, "call") => krate = Ident::new("$crate", Span::call_site()),
(_, x) => panic!("bad span {}", x),
}
quote!(
#[macro_export]
macro_rules! $ident {
($$i:ident) => {
use $krate::$$i as _;
};
}
)
}
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