Added specs for matching booleans and nil, and refactored the associa…

…ted matches in the parser into their own rules to make sure it only matches on those values.

lib/lupin/parser/parser.citrus

@@ -176,9 +176,8 @@ grammar Lupin::Parser::Lua
     ( table
     | number
     | string
-    | 'nil' { Lupin::AST::Nil.new }
-    | 'false' { Lupin::AST::False.new }
-    | 'true' { Lupin::AST::True.new }
+    | boolean
+    | nil
     )
   end
 
@@ -227,6 +226,18 @@ grammar Lupin::Parser::Lua
     | str: /\[(=*)\[.*?\]\1\]/m <Lupin::Parser::LongStringLiteral>
     )
   end
+
+  ### Boolean
+  rule boolean
+    ( 'false' { Lupin::AST::False.new }
+    | 'true' { Lupin::AST::True.new }
+    )
+  end
+
+  ### Nil
+  rule nil
+    'nil' { Lupin::AST::Nil.new }
+  end
 
   ### Whitespace and comments
   rule WS

spec/parser_spec.rb

@@ -34,6 +34,12 @@ def check (type, text)
     check(:string, "[==[foo\\\"bar\\'baz\\r\\n]==]") { "foo\\\"bar\\'baz\\r\\n" }
   end
 
+  it "matches booleans and nil" do
+    check(:boolean, "true") { true }
+    check(:boolean, "false") { false }
+    check(:nil, "nil") { nil }
+  end
+
   it "matches tables" do
     check(:table, "{}") { [:table] }
     check(:table, "{1}") { [:table, [:pair, nil, 1.0]] }