This Goa v3 design produces code that won't compile: ../../gen/http/items/server/types.go:42:6: NewItemResponse redeclared in this block

design.go

package design

import (
	. "goa.design/goa/v3/dsl"
)
var _ = API("gbug", func() {
	Server("gbug", func() {
        Host("development", func() {
            URI("http://localhost:8000/gbug")
        })
    })
})

var Item = Type("Item", func() {
    Attribute("name", String, "Name of item")
})

var _ = Service("items", func() {
	HTTP(func() {
		Path("/items")
	})
	Method("listPublic", func() {
		Description("List Public Items")
		Result(ArrayOf(Item))
		HTTP(func() {
			GET("/")
			Response(StatusOK)
		})
	})
	Method("listPrivate", func() {
		Description("List User-private Items")
		Payload(func() {
			Attribute("user", UInt32, "User ID")
		})
		Result(ArrayOf(Item))
		HTTP(func() {
			GET("/{user}")
			Response(StatusOK)
		})
	})
})