Add support for labels to Kotlin lexer

lib/rouge/lexers/kotlin.rb

@@ -53,6 +53,9 @@ class Kotlin < RegexLexer
           groups Keyword::Declaration, Text
           push :property
         end
+        rule %r'(return|continue|break|this|super)(@#{name})?' do
+          groups Keyword, Name::Decorator
+        end
         rule %r'\bfun\b', Keyword
         rule %r'\b(?:#{keywords.join('|')})\b', Keyword
         rule %r'^\s*\[.*?\]', Name::Attribute
@@ -78,6 +81,7 @@ class Kotlin < RegexLexer
         end
         rule class_name, Name::Class
         rule %r'(#{name})(?=\s*[({])', Name::Function
+        rule %r'(#{name})@', Name::Decorator # label
         rule name, Name
       end
 

spec/lexers/kotlin_spec.rb

@@ -23,5 +23,13 @@
     it 'recognizes one-line comments not followed by a newline (#797)' do
       assert_tokens_equal '// comment', ['Comment.Single', '// comment']
     end
+
+    it 'recognizes label' do
+      assert_tokens_equal 'label@', ["Name.Decorator", "label@"]
+    end
+
+    it 'recognizes label reference in break statement' do
+      assert_tokens_equal 'break@label', ["Keyword", "break"], ["Name.Decorator", "@label"]
+    end
   end
 end

spec/visual/samples/kotlin

@@ -172,4 +172,10 @@ fun anAnnotatedFunction() = {
 
 val (a, b) = pair
 
+loop@ for (i in 1..100) {
+    for (j in 1..100) {
+        if (...) break@loop
+    }
+}
+
 // comment at EOF (#797)