Add support for custom functions

smnp/newast/node/ret.py

@@ -0,0 +1,32 @@
+from smnp.newast.node.expression import ExpressionNode
+from smnp.newast.node.none import NoneNode
+from smnp.newast.node.statement import StatementNode
+from smnp.newast.parser import Parser
+from smnp.token.type import TokenType
+
+
+class ReturnNode(StatementNode):
+    def __init__(self, pos):
+        super().__init__(pos)
+        self.children.append(NoneNode())
+
+    @property
+    def value(self):
+        return self[0]
+
+    @value.setter
+    def value(self, value):
+        self[0] = value
+
+    @classmethod
+    def _parse(cls, input):
+        def createNode(ret, value):
+            node = ReturnNode(ret.pos)
+            node.value = value
+            return node
+
+        return Parser.allOf(
+            Parser.terminalParser(TokenType.RETURN),
+            ExpressionNode.parse,
+            createNode=createNode
+        )(input)