1 files changed, 7 insertions, 24 deletions
diff --git a/compiler/rustc_span/src/source_map.rs b/compiler/rustc_span/src/source_map.rs
index 8238a16969d..11ea5fe4ddf 100644
--- a/compiler/rustc_span/src/source_map.rs
+++ b/compiler/rustc_span/src/source_map.rs
@@ -1019,36 +1019,19 @@ impl SourceMap {
 
         let src = local_begin.sf.external_src.borrow();
 
-        // We need to extend the snippet to the end of the src rather than to end_index so when
-        // searching forwards for boundaries we've got somewhere to search.
-        let snippet = if let Some(ref src) = local_begin.sf.src {
-            &src[start_index..]
+        let snippet = if let Some(src) = &local_begin.sf.src {
+            src
         } else if let Some(src) = src.get_source() {
-            &src[start_index..]
+            src
         } else {
             return 1;
         };
-        debug!("snippet=`{:?}`", snippet);
 
-        let mut target = if forwards { end_index + 1 } else { end_index - 1 };
-        debug!("initial target=`{:?}`", target);
-
-        while !snippet.is_char_boundary(target - start_index) && target < source_len {
-            target = if forwards {
-                target + 1
-            } else {
-                match target.checked_sub(1) {
-                    Some(target) => target,
-                    None => {
-                        break;
-                    }
-                }
-            };
-            debug!("target=`{:?}`", target);
+        if forwards {
+            (snippet.ceil_char_boundary(end_index + 1) - end_index) as u32
+        } else {
+            (end_index - snippet.floor_char_boundary(end_index - 1)) as u32
         }
-        debug!("final target=`{:?}`", target);
-
-        if forwards { (target - end_index) as u32 } else { (end_index - target) as u32 }
     }
 
     pub fn get_source_file(&self, filename: &FileName) -> Option<Lrc<SourceFile>> {