Re-fontify buffer after it is reverted

Fix #104

Author: MicahChalmer

rust-mode-tests.el

@@ -2427,6 +2427,29 @@ Fontification needs to include this whole string or none of it.
       (should (<= font-lock-beg 1))
       (should (>= font-lock-end 12)))))
 
+(ert-deftest redo-syntax-after-change-far-from-point ()  
+  (let*
+      ((tmp-file-name (make-temp-file "rust-mdoe-test-issue104"))
+       (base-contents (apply 'concat (append '("fn foo() {\n\n}\n") (make-list 500 "// More stuff...\n") '("fn bar() {\n\n}\n")))))
+    ;; Create the temp file...
+    (with-temp-file tmp-file-name
+      (insert base-contents))
+    (with-temp-buffer
+      (insert-file-contents tmp-file-name 'VISIT nil nil 'REPLACE)
+      (rust-mode)
+      (goto-char (point-max))
+      (should (= 0 (rust-paren-level)))
+      (with-temp-file tmp-file-name
+        (insert base-contents)
+        (goto-char 12) ;; On the blank line in the middle of fn foo
+        (insert "    let z = 1 < 3;")
+        )
+      (revert-buffer 'IGNORE-AUTO 'NOCONFIRM 'PRESERVE-MODES)
+      (should (= 0 (rust-paren-level)))
+      )
+    )
+  )
+
 ;; If electric-pair-mode is available, load it and run the tests that use it.  If not,
 ;; no error--the tests will be skipped.
 (require 'elec-pair nil t)

rust-mode.el

@@ -1229,7 +1229,9 @@ This is written mainly to be used as `end-of-defun-function' for Rust."
   (setq-local beginning-of-defun-function 'rust-beginning-of-defun)
   (setq-local end-of-defun-function 'rust-end-of-defun)
   (setq-local parse-sexp-lookup-properties t)
-  (setq-local electric-pair-inhibit-predicate 'rust-electric-pair-inhibit-predicate-wrap))
+  (setq-local electric-pair-inhibit-predicate 'rust-electric-pair-inhibit-predicate-wrap)
+  (add-hook 'after-revert-hook 'rust--after-revert-hook 'LOCAL)
+  )
 
 ;;;###autoload
 (add-to-list 'auto-mode-alist '("\\.rs\\'" . rust-mode))
@@ -1240,6 +1242,17 @@ This is written mainly to be used as `end-of-defun-function' for Rust."
   (require 'rust-mode)
   (rust-mode))
 
+;; Issue #104: When reverting the buffer, make sure all fontification is redone
+;; so that we don't end up missing a non-angle-bracket '<' or '>' character.
+(defun rust--after-revert-hook ()
+  (let
+      ;; Newer emacs versions (25 and later) make `font-lock-fontify-buffer'
+      ;; interactive-only, and want lisp code to call `font-lock-flush' or
+      ;; `font-lock-ensure'.  But those don't exist in emacs 24 and earlier.
+      ((font-lock-ensure-fn (if (fboundp 'font-lock-ensure) 'font-lock-ensure 'font-lock-fontify-buffer)))
+    (funcall font-lock-ensure-fn))
+  )
+
 ;; Issue #6887: Rather than inheriting the 'gnu compilation error
 ;; regexp (which is broken on a few edge cases), add our own 'rust
 ;; compilation error regexp and use it instead.