1use crate::ToTokens;
2use proc_macro2::extra::DelimSpan;
3use proc_macro2::{Span, TokenStream};
4
5// Not public API other than via the syn crate. Use syn::spanned::Spanned.
6pub trait Spanned: private::Sealed {
7 fn __span(&self) -> Span;
8}
9
10impl Spanned for Span {
11 fn __span(&self) -> Span {
12 *self
13 }
14}
15
16impl Spanned for DelimSpan {
17 fn __span(&self) -> Span {
18 self.join()
19 }
20}
21
22impl<T: ?Sized + ToTokens> Spanned for T {
23 fn __span(&self) -> Span {
24 join_spans(self.into_token_stream())
25 }
26}
27
28fn join_spans(tokens: TokenStream) -> Span {
29 let mut iter: impl Iterator = tokens.into_iter().map(|tt: TokenTree| tt.span());
30
31 let first: Span = match iter.next() {
32 Some(span: Span) => span,
33 None => return Span::call_site(),
34 };
35
36 iter.fold(None, |_prev, next| Some(next))
37 .and_then(|last| first.join(last))
38 .unwrap_or(default:first)
39}
40
41mod private {
42 use crate::ToTokens;
43 use proc_macro2::extra::DelimSpan;
44 use proc_macro2::Span;
45
46 pub trait Sealed {}
47 impl Sealed for Span {}
48 impl Sealed for DelimSpan {}
49 impl<T: ?Sized + ToTokens> Sealed for T {}
50}
51