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#![feature(proc_macro_def_site)]
#![feature(proc_macro_diagnostic)]
#![feature(proc_macro_quote)]
extern crate proc_macro;
use proc_macro::*;
#[proc_macro]
pub fn resolve_located_at(input: TokenStream) -> TokenStream {
match &*input.into_iter().collect::<Vec<_>>() {
[a, b, ..] => {
// The error is reported at input `a`.
let mut diag = Diagnostic::new(Level::Error, "expected error");
diag.set_spans(Span::def_site().located_at(a.span()));
diag.emit();
// Resolves to `struct S;` at def site, but the error is reported at input `b`.
let s = TokenTree::Ident(Ident::new("S", b.span().resolved_at(Span::def_site())));
quote!({
struct S;
$s
})
}
_ => panic!("unexpected input"),
}
}
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