language: none support

parser/src/main/kotlin/gay/pizza/pork/parser/Parser.kt

@@ -192,6 +192,11 @@ class Parser(source: PeekableSource<Token>, val attribution: NodeAttribution) {
         Continue()
       }
 
+      TokenType.None -> {
+        expect(TokenType.None)
+        NoneLiteral()
+      }
+
       else -> {
         throw ParseError(
           "Failed to parse token: ${token.type} '${token.text}' as" +

parser/src/main/kotlin/gay/pizza/pork/parser/Printer.kt

@@ -81,6 +81,10 @@ class Printer(buffer: StringBuilder) : NodeVisitor<Unit> {
     visit(node.definition)
   }
 
+  override fun visitNoneLiteral(node: NoneLiteral) {
+    append("none")
+  }
+
   override fun visitSymbol(node: Symbol) {
     append(node.id)
   }

parser/src/main/kotlin/gay/pizza/pork/parser/TokenType.kt

@@ -14,7 +14,8 @@ enum class TokenType(vararg properties: TokenTypeProperty) {
   StringLiteral(StringLiteralFamily),
   Equality(OperatorFamily),
   Inequality(ManyChars("!="), OperatorFamily),
-  ExclaimationPoint(SingleChar('!'), Promotion('=', Inequality)),
+  ExclamationPoint(SingleChar('!'), Promotion('=', Inequality)),
+  None(ManyChars("None"), KeywordFamily),
   Equals(SingleChar('='), Promotion('=', Equality)),
   PlusPlus(ManyChars("++"), OperatorFamily),
   MinusMinus(ManyChars("--"), OperatorFamily),