Typescript 函数参数类型推断问题

Question

我这里有这段代码：

export default function (triggerEl: Ref<HTMLDivElement>, contentEl: Ref<HTMLDivElement>, placement: Ref<Placement> | Placement = 'auto', offset: Ref<number> | number = 0) {

  placement = ref(placement) as Ref<Placement>
  offset = ref(offset)

  const { top: triggerTop, right: triggerRight, bottom: triggerBottom, left: triggerLeft, width: triggerWidth, height: triggerHeight } = useElementBounding(triggerEl)
  const { top: contentTop, right: contentRight, bottom: contentBottom, left: contentLeft, width: contentWidth, height: contentHeight } = useElementBounding(contentEl)


  const position = computed<PopperPosition>(() => {
    let top = Number.MIN_SAFE_INTEGER
    let left = Number.MIN_SAFE_INTEGER

    if (placement.value === 'top') {
      top = triggerTop.value - contentHeight.value - offset.value
      left = triggerLeft.value + triggerWidth.value / 2 - contentWidth.value / 2
    }

    return {
      top,
      left,
    }
  })



  return  null
}

我已经将'placement'和'offset'参数转换为它们对应的'Ref'类型，但下面的代码仍然认为它们是类型 Ref |数字，所以它抱怨，但他们实际上永远不会是数字类型。

我如何解决这里的打字检查问题？？？

Answer 1

我想弄乱 TS 推理的来源位于第 21 和 22 行（重新分配变量值）：

placement = ref(placement) as Ref<Placement>
offset = ref(offset)

我建议改为创建新变量，因此最终代码将如下所示：

export default function (triggerEl: Ref<HTMLDivElement>, contentEl: Ref<HTMLDivElement>, placement: Ref<Placement> | Placement = 'auto', offset: Ref<number> | number = 0) {

  const placementRef = ref(placement)
  const offsetRef = ref(offset)

  const { top: triggerTop, right: triggerRight, bottom: triggerBottom, left: triggerLeft, width: triggerWidth, height: triggerHeight } = useElementBounding(triggerEl)
  const { top: contentTop, right: contentRight, bottom: contentBottom, left: contentLeft, width: contentWidth, height: contentHeight } = useElementBounding(contentEl)


  const position = computed<PopperPosition>(() => {
    let top = Number.MIN_SAFE_INTEGER
    let left = Number.MIN_SAFE_INTEGER

    if (placementRef.value === 'top') {
      top = triggerTop.value - contentHeight.value - offsetRef.value
      left = triggerLeft.value + triggerWidth.value / 2 - contentWidth.value / 2
    }

    return {
      top,
      left,
    }
  })



  return  null
}