[Swift] Support tuple destructuring

lib/rouge/lexers/swift.rb

@@ -107,6 +107,11 @@ class deinit enum extension final func import init internal lazy let optional pr
           groups Keyword, Text, Name::Variable
         end
 
+        rule /(let|var)\b(\s*)([(])/ do
+          groups Keyword, Text, Punctuation
+          push :tuple
+        end
+
         rule /(?!\b(if|while|for|private|internal|unowned|switch|case)\b)\b#{id}(?=(\?|!)?\s*[(])/ do |m|
           if m[0] =~ /^[[:upper:]]/
             token Keyword::Type
@@ -137,10 +142,18 @@ class deinit enum extension final func import init internal lazy let optional pr
         end
 
         rule /(`)(#{id})(`)/ do
-          groups Punctuation,Name,Punctuation
+          groups Punctuation, Name, Punctuation
         end
       end
 
+      state :tuple do
+        rule /(#{id})/, Name::Variable
+        rule /,/, Punctuation
+        rule /[(]/, Punctuation, :push
+        rule /[)]/, Punctuation, :pop!
+        mixin :inline_whitespace
+      end
+
       state :dq do
         rule /\\[\\0tnr'"]/, Str::Escape
         rule /\\[(]/, Str::Escape, :interp