我尝试连接一些条形码值：

barcodeScanner.process(image)
    .addOnSuccessListener {
        barcodes ->
            if (barcodes.isNotEmpty()) {
                val barcode = barcodes.reduce {acc, barcode -> acc + barcode.rawValue() }
                debug ("analyze: barcodes: $barcode")
            } else {
                debug ("analyze: No barcode scanned")
            }
    }

程式码会产生下列错误：

Type mismatch: inferred type is Unit but Barcode! was expected
Unresolved reference. None of the following candidates is applicable because of receiver type mismatch: 
public operator fun Offset.plus(offset: IntOffset): Offset defined in androidx.compose.ui.unit
public operator fun IntOffset.plus(offset: Offset): Offset defined in androidx.compose.ui.unit
Expression 'rawValue' of type 'String?' cannot be invoked as a function. The function 'invoke()' is not found

我一个都不懂。谁能解释一下吗？
特别是最后一条错误信息听起来很奇怪。为什么我要在String上调用rawValue呢？变量barcodes应该是List<Barcode>而不是List<String>。