Auto merge of #46381 - estebank:expected-span, r=nikomatsakis

Point to next token when it is in the expected line

r? @nikomatsakis

2 files changed, 23 insertions, 6 deletions

diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index 3aac5334a38..3906ed431ce 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -358,7 +358,7 @@ impl CodeMap {
     }
 
     // If the relevant filemap is empty, we don't return a line number.
-    fn lookup_line(&self, pos: BytePos) -> Result<FileMapAndLine, Rc<FileMap>> {
+    pub fn lookup_line(&self, pos: BytePos) -> Result<FileMapAndLine, Rc<FileMap>> {
         let idx = self.lookup_filemap_idx(pos);
 
         let files = self.files.borrow();
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index a02c6b764b7..2461e65585f 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -660,11 +660,28 @@ impl<'a> Parser<'a> {
             } else {
                 label_sp
             };
-            if self.span.contains(sp) {
-                err.span_label(self.span, label_exp);
-            } else {
-                err.span_label(sp, label_exp);
-                err.span_label(self.span, "unexpected token");
+
+            let cm = self.sess.codemap();
+            match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
+                (Ok(ref a), Ok(ref b)) if a.line == b.line => {
+                    // When the spans are in the same line, it means that the only content between
+                    // them is whitespace, point at the found token in that case:
+                    //
+                    // X |     () => { syntax error };
+                    //   |                    ^^^^^ expected one of 8 possible tokens here
+                    //
+                    // instead of having:
+                    //
+                    // X |     () => { syntax error };
+                    //   |                   -^^^^^ unexpected token
+                    //   |                   |
+                    //   |                   expected one of 8 possible tokens here
+                    err.span_label(self.span, label_exp);
+                }
+                _ => {
+                    err.span_label(sp, label_exp);
+                    err.span_label(self.span, "unexpected token");
+                }
             }
             Err(err)
         }