70 lines
2.8 KiB
Rust
70 lines
2.8 KiB
Rust
extern crate proc_macro;
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use proc_macro::{Delimiter, Group, Ident, Span, TokenStream, TokenTree, token_stream};
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fn read_ident(iter: &mut token_stream::IntoIter) -> Ident {
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match iter.next() {
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Some(TokenTree::Ident(i)) => i,
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_ => panic!("expected ident"),
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}
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}
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#[proc_macro_derive(DeriveBadSpan)]
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pub fn derive_bad_span(input: TokenStream) -> TokenStream {
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let mut input = input.into_iter();
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assert_eq!(read_ident(&mut input).to_string(), "struct");
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let ident = read_ident(&mut input);
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let mut tys = match input.next() {
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Some(TokenTree::Group(g)) if g.delimiter() == Delimiter::Parenthesis => g.stream().into_iter(),
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_ => panic!(),
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};
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let field1 = read_ident(&mut tys);
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tys.next();
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let field2 = read_ident(&mut tys);
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<TokenStream as FromIterator<TokenTree>>::from_iter(
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[
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Ident::new("impl", Span::call_site()).into(),
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ident.into(),
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Group::new(
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Delimiter::Brace,
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<TokenStream as FromIterator<TokenTree>>::from_iter(
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[
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Ident::new("fn", Span::call_site()).into(),
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Ident::new("_foo", Span::call_site()).into(),
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Group::new(Delimiter::Parenthesis, TokenStream::new()).into(),
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Group::new(
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Delimiter::Brace,
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<TokenStream as FromIterator<TokenTree>>::from_iter(
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[
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Ident::new("if", field1.span()).into(),
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Ident::new("true", field1.span()).into(),
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{
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let mut group = Group::new(Delimiter::Brace, TokenStream::new());
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group.set_span(field1.span());
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group.into()
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},
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Ident::new("if", field2.span()).into(),
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Ident::new("true", field2.span()).into(),
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{
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let mut group = Group::new(Delimiter::Brace, TokenStream::new());
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group.set_span(field2.span());
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group.into()
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},
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]
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.iter()
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.cloned(),
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),
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)
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.into(),
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]
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.iter()
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.cloned(),
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),
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)
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.into(),
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]
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.iter()
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.cloned(),
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)
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}
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