Recognize runaway raw strings

Recognize raw strings all the way to the end of the buffer if they are
not closed.  This is not valid rust code, but the highlighting should
show the mistake.

This also eliminates glitchy behavior that can occur in this situation.
Emacs assumes that edits can't change syntax at positions before the
edit, and raw strings without this change violated this.

Author: MicahChalmer

rust-mode-tests.el

@@ -1110,6 +1110,41 @@ this_is_not_a_string();)"
     (should (equal nil (get-text-property 28 'face))) ;; Semicolon--should not be part of the string
     ))
 
+(ert-deftest font-lock-runaway-raw-string ()
+  (rust-test-font-lock
+   "const Z = r#\"my raw string\";\n// oops this is still in the string"
+   '("const" font-lock-keyword-face
+     "Z" font-lock-type-face
+     "r#\"my raw string\";\n// oops this is still in the string" font-lock-string-face))
+  )
+
+(ert-deftest font-lock-recognize-closing-raw-string ()
+  (with-temp-buffer
+    (rust-mode)
+    (insert "const foo = r##\"
+1...............................................50
+1...............................................50
+1...............................................50
+1...............195-->\"; let ...................50
+1...............................................50
+1...............................................50
+1...............................................50
+1...............................................50
+1...............................................50
+1......................500......................50
+\"#;
+")
+    (font-lock-fontify-buffer)
+    (goto-char 530)
+    (insert "#")
+    ;; We have now closed the raw string.  Check that the whole string is
+    ;; recognized after the change
+    (font-lock-after-change-function (1- (point)) (point) 0)
+    (should (equal 'font-lock-string-face (get-text-property 195 'face))) ;; The "let"
+    (should (equal 'font-lock-string-face (get-text-property 500 'face))) ;; The "500"
+    (should (equal nil (get-text-property 531 'face))) ;; The second ";"
+    ))
+
 ;;; Documentation comments
 
 (ert-deftest font-lock-doc-line-comment-parent ()

rust-mode.el

@@ -531,7 +531,10 @@
 
       ;; No "#"s - capture the ending quote (using a backref to group 3,
       ;; so that we can't match a quote if we had "#"s) as group 6
-      (group (backref 3))))
+      (group (backref 3))
+
+      ;; If the raw string wasn't actually closed, go all the way to the end
+      string-end))
 
     ;; Character literal: match the beginning ' of a character literal
     ;; as group 7, and the ending one as group 8