spanned.rs

 1// SPDX-License-Identifier: Apache-2.0 OR MIT
 2
 3use crate::ToTokens;
 4use proc_macro2::extra::DelimSpan;
 5use proc_macro2::{Span, TokenStream};
 6
 7// Not public API other than via the syn crate. Use syn::spanned::Spanned.
 8pub trait Spanned: private::Sealed {
 9    fn __span(&self) -> Span;
10}
11
12impl Spanned for Span {
13    fn __span(&self) -> Span {
14        *self
15    }
16}
17
18impl Spanned for DelimSpan {
19    fn __span(&self) -> Span {
20        self.join()
21    }
22}
23
24impl<T: ?Sized + ToTokens> Spanned for T {
25    fn __span(&self) -> Span {
26        join_spans(self.into_token_stream())
27    }
28}
29
30fn join_spans(tokens: TokenStream) -> Span {
31    let mut iter = tokens.into_iter().map(|tt| tt.span());
32
33    let first = match iter.next() {
34        Some(span) => span,
35        None => return Span::call_site(),
36    };
37
38    iter.fold(None, |_prev, next| Some(next))
39        .and_then(|last| first.join(last))
40        .unwrap_or(first)
41}
42
43mod private {
44    use crate::ToTokens;
45    use proc_macro2::extra::DelimSpan;
46    use proc_macro2::Span;
47
48    pub trait Sealed {}
49    impl Sealed for Span {}
50    impl Sealed for DelimSpan {}
51    impl<T: ?Sized + ToTokens> Sealed for T {}
52}