ruby-syntax-propertize: Fix certain cases following ::

* lisp/progmodes/ruby-mode.el (ruby-syntax-propertize):
Make sure to backtrack if the "symbols with special characters"
rule is aborted because of preceding colon.

lisp/progmodes/ruby-mode.el

@@ -1869,8 +1869,8 @@ It will be properly highlighted even when the call omits parens.")
       ;; Symbols with special characters.
       (":\\([-+~]@?\\|[/%&|^`]\\|\\*\\*?\\|<\\(<\\|=>?\\)?\\|>[>=]?\\|===?\\|=~\\|![~=]?\\|\\[\\]=?\\)"
        (1 (unless (or
-                   (eq (char-before (match-beginning 0)) ?:)
-                   (nth 8 (syntax-ppss (match-beginning 1))))
+                   (nth 8 (syntax-ppss (match-beginning 1)))
+                   (eq (char-before (match-beginning 0)) ?:))
             (goto-char (match-end 0))
             (string-to-syntax "_"))))
       ;; Symbols ending with '=' (bug#42846).

test/lisp/progmodes/ruby-mode-resources/ruby.rb

@@ -108,7 +108,7 @@ def foo
 # Multiline regexp.
 /bars
  tees # toots
- nfoos/
+ nfoos::/
 
 def test1(arg)
   puts "hello"