syntax_pos: Introduce a helper for checking whether a span comes from expansion

3 files changed, 8 insertions, 3 deletions

diff --git a/src/libsyntax_pos/hygiene.rs b/src/libsyntax_pos/hygiene.rs
index f91a2291544..4132b99cf41 100644
--- a/src/libsyntax_pos/hygiene.rs
+++ b/src/libsyntax_pos/hygiene.rs
@@ -255,7 +255,7 @@ impl HygieneData {
     }
 
     fn walk_chain(&self, mut span: Span, to: SyntaxContext) -> Span {
-        while span.ctxt() != crate::NO_EXPANSION && span.ctxt() != to {
+        while span.from_expansion() && span.ctxt() != to {
             if let Some(info) = self.expn_info(self.outer_expn(span.ctxt())) {
                 span = info.call_site;
             } else {
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 02a7433d946..793710b453f 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -288,6 +288,12 @@ impl Span {
         span.lo.0 == 0 && span.hi.0 == 0
     }
 
+    /// Returns `true` if this span comes from a macro or desugaring.
+    #[inline]
+    pub fn from_expansion(self) -> bool {
+        self.ctxt() != SyntaxContext::empty()
+    }
+
     /// Returns a new span representing an empty span at the beginning of this span
     #[inline]
     pub fn shrink_to_lo(self) -> Span {
diff --git a/src/libsyntax_pos/symbol.rs b/src/libsyntax_pos/symbol.rs
index 2d9556233d1..6f5a458a874 100644
--- a/src/libsyntax_pos/symbol.rs
+++ b/src/libsyntax_pos/symbol.rs
@@ -14,7 +14,6 @@ use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::str;
 
-use crate::hygiene::SyntaxContext;
 use crate::{Span, DUMMY_SP, GLOBALS};
 
 #[cfg(test)]
@@ -851,7 +850,7 @@ impl fmt::Display for Ident {
 
 impl Encodable for Ident {
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
-        if self.span.ctxt().modern() == SyntaxContext::empty() {
+        if !self.span.modern().from_expansion() {
             s.emit_str(&self.as_str())
         } else { // FIXME(jseyfried): intercrate hygiene
             let mut string = "#".to_owned();