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Auto merge of #55780 - ogoffart:span_source_text, r=petrochenkov

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Introduce proc_macro::Span::source_text

A function to extract the actual source behind a Span.

Background: I would like to use `syn` in a `build.rs` script to parse the rust code, and extract part of the source code. However, `syn` only gives access to proc_macro2::Span, and i would like to get the source code behind that.
I opened an issue on proc_macro2 bug tracker for this feature https://github.com/alexcrichton/proc-macro2/issues/110  and @alexcrichton said the feature should first go upstream in proc_macro.  So there it is!

Since most of the Span API is unstable anyway, this is guarded by the same `proc_macro_span` feature as everything else.
This commit is contained in:
bors 2019-03-27 08:58:40 +00:00
commit c5fb4d0d2f
5 changed files with 59 additions and 2 deletions
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3
src/libsyntax_ext/proc_macro_server.rs
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@ -740,4 +740,7 @@ impl server::Span for Rustc<'_> {
fn resolved_at(&mut self, span: Self::Span, at: Self::Span) -> Self::Span {
span.with_ctxt(at.ctxt())
}
fn source_text(&mut self, span: Self::Span) -> Option<String> {
self.sess.source_map().span_to_snippet(span).ok()
}
}