| 1 | use std::iter::FromIterator; |
| 2 | |
|---|
| 3 | use proc_macro2::{Group, Span, TokenStream, TokenTree}; |
|---|
| 4 | |
|---|
| 5 | /// Deeply change the span of some tokens, ensuring that the output only references `span`. |
|---|
| 6 | /// |
|---|
| 7 | /// Macros such as `quote_spanned` preserve the spans of interpolated tokens, which is useful. |
|---|
| 8 | /// However, in some very specific scenarios it is desirable to suppress the original span |
|---|
| 9 | /// information in favor of a different one. |
|---|
| 10 | /// |
|---|
| 11 | /// For more information, see [dtolnay/syn#309](https://github.com/dtolnay/syn/issues/309). |
|---|
| 12 | pub(crate) fn change_span(tokens: TokenStream, span: Span) -> TokenStream { |
|---|
| 13 | let mut result: Vec = vec![]; |
|---|
| 14 | for mut token: TokenTree in tokens { |
|---|
| 15 | match token { |
|---|
| 16 | TokenTree::Group(group: Group) => { |
|---|
| 17 | let mut new_group: Group = |
|---|
| 18 | Group::new(group.delimiter(), stream:change_span(tokens:group.stream(), span)); |
|---|
| 19 | new_group.set_span(span); |
|---|
| 20 | result.push(TokenTree::Group(new_group)); |
|---|
| 21 | } |
|---|
| 22 | _ => { |
|---|
| 23 | token.set_span(span); |
|---|
| 24 | result.push(token); |
|---|
| 25 | } |
|---|
| 26 | } |
|---|
| 27 | } |
|---|
| 28 | FromIterator::from_iter(result.into_iter()) |
|---|
| 29 | } |
|---|
| 30 | |
|---|
