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#![feature(proc_macro_diagnostic, proc_macro_span, proc_macro_def_site)]
extern crate proc_macro;
use proc_macro::{TokenStream, TokenTree, Span, Diagnostic};
fn parse(input: TokenStream) -> Result<(), Diagnostic> {
let mut hi_spans = vec![];
for tree in input {
if let TokenTree::Ident(ref ident) = tree {
if ident.to_string() == "hi" {
hi_spans.push(ident.span());
}
}
}
if !hi_spans.is_empty() {
return Err(Span::def_site()
.error("hello to you, too!")
.span_note(hi_spans, "found these 'hi's"));
}
Ok(())
}
#[proc_macro]
pub fn hello(input: TokenStream) -> TokenStream {
if let Err(diag) = parse(input) {
diag.emit();
}
TokenStream::new()
}
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