Generic Type Issue

[lacherogwu]

Vue version

3.5

Link to minimal reproduction

https://play.vuejs.org/#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

Steps to reproduce

create a custom component with a generic T, defineModel and defineEmits like the code below

<script setup lang="ts" generic="T extends Item, U extends T">

export type Item = {
  text: string;
  value: string
}

const props = defineProps<{ items: T[] }>()
const model = defineModel<U[]>()

defineEmits<{
  'update:modelValue': [items: U[]]
}>()

</script>

<template>
  <div>
    <slot />
  </div>
</template>

and from you parent component use this

<script setup>
import { ref } from 'vue'
import Comp from './Comp.vue';

const myModel = ref([{
  text: 'text', value: 'value'
}])

</script>

<template>
  <Comp v-model="myModel" :items="[{ text: 'some item', value: 'some item' }]" @update:modelValue=""></Comp>
</template>

and if I hover the @update:modelValue I get unknown args instead of T

What is expected?

I should see the type of T when hover on @update:modelValue

What is actually happening?

I found out this this happens only on vue 3.5, when using 3.4 it works well

3.5

3.4

I also noticed that this happens only for @update:modelValue, for example if I have @update:modelAnythingElse in vue 3.5 it works just fine

and I also noticed that only if I call the defineEmits() in the child component this happens
if I don't call the defineEmits() the types are correct on the default @update:modelValue

System Info

System:
    OS: macOS 14.6.1
    CPU: (14) arm64 Apple M3 Max
    Memory: 167.28 MB / 36.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.16.0 - ~/.nvm/versions/node/v20.16.0/bin/node
    npm: 10.8.1 - ~/.nvm/versions/node/v20.16.0/bin/npm
    pnpm: 9.0.6 - /opt/homebrew/bin/pnpm
    Watchman: 2024.10.14.00 - /opt/homebrew/bin/watchman
  Browsers:
    Brave Browser: 127.1.68.128
    Chrome: 130.0.6723.58
    Safari: 17.6

Any additional comments?

No response

[jacksongross]

I am seeing the same, even without generics. The workaround I found so far is to define the emits with the regular type-based syntax as per the docs, so in your case would be:

defineEmits<{
  (e: 'update:modelValue': items: U[]): void;
}>()

It would be good if we could have the types inferred correctly with the succinct syntax.

[KazariEX]

It is not necessary to use both defineEmits to specify the update event for modelValue, as it is automatically generated.