function reportVSlot(vSlotAttr) {
      context.report({
        node: vSlotAttr.key,
        messageId: 'forbiddenVSlot',
        // fix to use `slot` (downgrade)
        fix(fixer) {
          if (!canConvertToSlot(vSlotAttr)) {
            return null
          }
          return fixVSlotToSlot(fixer, vSlotAttr)
        }
      })
    }
Reports `v-slot` node
@param {VDirective} vSlotAttr node of `v-slot`
@returns {void}