(
#comment
(let config (DataSource 'config))

(let res_sink (DataSink 'result))
(let vt (VariantType (TupleType (DataType 'Int32))))
(let v1 (Variant (Int32 '34) '0 vt))

(let handler (lambda '(x) (+ (Int32 '100) x)))

(let world (Write! world res_sink (Key) (Visit v1 '0 handler) '('('type))))
(let world (Write! world res_sink (Key) (Visit v1 '0 handler (Int32 '999)) '('('type))))

(let vt (VariantType (StructType '('a (DataType 'Int32)))))
(let v1 (Variant (Int32 '34) 'a vt))

(let world (Write! world res_sink (Key) (Visit v1 'a handler) '('('type))))
(let world (Write! world res_sink (Key) (Visit v1 'a handler (Int32 '999)) '('('type))))

(let world (Commit! world res_sink))
(return world)
)