fixes for updated grammar

include/statement_nodes.hpp

@@ -0,0 +1,27 @@
+#pragma once
+
+#include "basic_nodes.hpp"
+
+#include <vector>
+
+// IN PROGRESS
+
+namespace nodes {
+
+class Import : public Node {
+public:
+private:
+  Identifier import_name_;
+  Identifier module_name_;
+  std::vector<Identifier> symbols_;
+}; // IN PROGRESS
+
+class Constraint : public Node {}; // IN PROGRESS
+
+class TypeDefinition : public Node {}; // IN PROGRESS
+
+class FunctionDefinition : public Node {}; // IN PROGRESS
+
+class TypeclassDefinition : public Node {}; // IN PROGRESS
+
+} // namespace nodes