Fix treesit_sync_visible_region's range fixup code (bug#73264)

      new_ranges_head
      |
      v
( )->( )->( )->( )->( )
           ^    ^
           |    |
           |    lisp_ranges (loop head)
           |
           prev_cons -> set cdr to nil to cut of the rest

result:

     ( )->( )

* src/treesit.c (treesit_sync_visible_region): Cut off this cons and the
rest, not set the current range's end to nil.
* test/src/treesit-tests.el:
(treesit-range-fixup-after-edit): Add tests for all cases.

1 files changed, 31 insertions, 1 deletions

diff --git a/test/src/treesit-tests.el b/test/src/treesit-tests.el
index 98aaeb62781..68ed6ca751f 100644
--- a/test/src/treesit-tests.el
+++ b/test/src/treesit-tests.el
@@ -709,7 +709,37 @@ visible_end.)"
                      '((1 . 7) (10 . 15))))
       (narrow-to-region 5 13)
       (should (equal (treesit-parser-included-ranges parser)
-                     '((5 . 7) (10 . 13)))))))
+                     '((5 . 7) (10 . 13))))
+
+      ;; Narrow in front.
+      (widen)
+      (treesit-parser-set-included-ranges parser '((4 . 17)))
+      ;; 11111111111111111111
+      ;;    [           ]
+      ;; {     } narrow
+      (narrow-to-region 1 8)
+      (should (equal (treesit-parser-included-ranges parser)
+                     '((4 . 8))))
+
+      ;; Narrow in back.
+      (widen)
+      (treesit-parser-set-included-ranges parser '((4 . 17)))
+      ;; 11111111111111111111
+      ;;    [           ]
+      ;;              {     } narrow
+      (narrow-to-region 15 20)
+      (should (equal (treesit-parser-included-ranges parser)
+                     '((15 . 17))))
+
+      ;; No overlap
+      (widen)
+      (treesit-parser-set-included-ranges parser '((15 . 20)))
+      ;; 11111111111111111111
+      ;;    [           ]
+      ;;              {     } narrow
+      (narrow-to-region 1 10)
+      (should (equal (treesit-parser-included-ranges parser)
+                     nil)))))
 
 ;;; Multiple language