types                = make(map[reflect.Type]gobType, 32)
	idToTypeSlice        = make([]gobType, 1, firstUserId)
	builtinIdToTypeSlice [firstUserId]gobType // set in init() after builtins are established
)

func idToType(id typeId) gobType {
	if id < 0 || int(id) >= len(idToTypeSlice) {
		return nil
	}
	return idToTypeSlice[id]
}

func builtinIdToType(id typeId) gobType {

	}
}

// typeString returns a human-readable description of the type identified by remoteId.
func (dec *Decoder) typeString(remoteId typeId) string {
	typeLock.Lock()
	defer typeLock.Unlock()
	if t := idToType(remoteId); t != nil {
		// globally known type.
		return t.string()
	}
	return dec.wireType[remoteId].string()
}

// compileSingle compiles the decoder engine for a non-struct top-level value, including