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