[Sass] Added deprecation warning about the upcoming change to silent comments.

lib/sass/engine.rb

@@ -136,6 +136,7 @@ module Sass
     def split_lines
       @line = 0
       old_tabs = nil
+      last_line_was_comment = false
       @template.each_with_index do |line, index|
         @line += 1
 
@@ -143,6 +144,19 @@ module Sass
 
         if line[0] == COMMENT_CHAR && line[1] == SASS_COMMENT_CHAR && tabs == 0
           tabs = old_tabs
+          last_line_was_comment = true
+        elsif last_line_was_comment && tabs
+          if tabs > 0
+            context = "On line #{@line}"
+            context << " of #{@options[:filename]}" if @options[:filename]
+            warn <<ENDENDEND
+DEPRECATION WARNING:
+#{context}
+Silent comments (//) in version 2.2 will comment out the lines indented beneath them.
+Please indent line #{@line - 1} to match the surrounding indentation level
+ENDENDEND
+          end
+          last_line_was_comment = false
         end
 
         if tabs # if line isn't blank

test/sass/engine_test.rb

@@ -98,7 +98,13 @@ END
   end
 
   def test_exception_line
-    to_render = "rule\n  :attr val\n// comment!\n\n  :broken\n"
+    to_render = <<SASS
+rule
+  :attr val
+  // comment!
+
+  :broken
+SASS
     begin
       Sass::Engine.new(to_render).render
     rescue Sass::SyntaxError => err

test/sass/templates/complex.sass

@@ -79,7 +79,6 @@ body
         :margin 0 5px
         :padding 5px 5px 0 5px
         :display inline
-// This comment is in the middle of this rule
         :font-size 1.1em
         // This comment is properly indented
         :color #fff