incr.comp.: Store Spans as (file,line,col,length) in incr.comp. cache.

The previous method ran into problems because ICH would treat Spans
as (file,line,col) but the cache contained byte offsets and its
possible for the latter to change while the former stayed stable.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 47755dc1d54..bf059cac891 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -931,6 +931,11 @@ impl FileMap {
             (lines[line_index], lines[line_index + 1])
         }
     }
+
+    #[inline]
+    pub fn contains(&self, byte_pos: BytePos) -> bool {
+        byte_pos >= self.start_pos && byte_pos <= self.end_pos
+    }
 }
 
 /// Remove utf-8 BOM if any.