v-else-if does not report TS error in some cases

[rasmus0201]

Vue - Official extension or vue-tsc version

2.2.0

VSCode version

1.96.4

Vue version

3.5.13

TypeScript version

5.7.2

System Info

package.json dependencies

{
  "dependencies": {
    "vue": "^3.5"
  },
  "devDependencies": {
    "@types/node": "^22.10.1",
    "@vitejs/plugin-vue": "^5.0.4",
    "eslint": "^9.15.0",
    "prettier": "^3.2.5",
    "typescript": "^5.7.2",
    "vite": "^6.0.4",
    "vue-tsc": "^2.1.10"
  }
}

(only a portion of our dependencies, but should be representative)

Steps to reproduce

<script setup lang="ts">
import { ref } from "vue";

type Presentation = {
  source: "local" | "remote";
  stream: MediaStream;
};

const isPresentationPrimary = ref<boolean>(true);

const presentation = ref<Presentation | undefined>();
</script>

<template>
  <div>
    <p v-if="!isPresentationPrimary">Presentation is not primary</p>

    <!-- This does not work (missing TS error): -->
    <p v-else-if="presentation.stream && isPresentationPrimary">Show presentation as primary, if it exists</p>

    <!-- This works (gives TS error): -->
    <!-- <p v-else-if="presentation.stream">Show presentation as primary, if it exists</p> -->
  </div>
</template>

1. Use the snippet, notice that in VS Code and vue-tsc, you won't get TS error about presentation possibly being undefined for the v-else-if="presentation.stream && isPresentationPrimary"
2. Comment out the line, and enable the

   below - notice that you now got an error as expected

What is expected?

vue-tsc should throw an error about presentation possibly being undefined.

What is actually happening?

No errors, compiles just fine

Link to minimal reproduction

https://play.vuejs.org/#eNqVk1Fr2zAQx7/KVQ9tConDyPbiuYFt9GGDbWXJo2Bo9tlRK0tCkp2UNN99J5lkzggdexBId3/d/e502rMP1mZ9hyxnhS+dtAE8hs6CErq54yx4zpZcy9YaF2APDms4QO1MCzd07YZrrsOzRXhw6FEHEaTRcAd7rgG86VyJOXCmTCkUZ/BCe4etCcjZ+yQJDkWbw1espFilA9kPtLgujfYBpB+HfnCyFe6ZMhBJ8csYhUIvJ8F1eDu6ZM9povYM8AU6XWEtNVbLSbxYzIfqqVY6BGytEgHpBFBUsk8b2lroZ7KmvlxdxKJenaWRHrSJNMlbzG0KnyJdzWaw3pCgMjiotsY9waSV3kvdwHoF6JxxtznMZuP0qDwODOMis6GRcH19uWFEttqY7XljhD+iTUHWIAPgTvrgB1BK+DdrRPQwaWRPzBcJo/TfmP9Nc8xQzIfHKOanJ2JTGlJ69Vo22aM3miY5DR9npWmtVOi+2xifBjkfxjL6hFJm+yXZ4uxMj/Zyg+XTBfuj30UbZ6m3rqf5PfmCcA2GwX2/+oY72p+crak6RepXnD/QG9VFxkH2kWaTsEe6RPs5/UGajbW/3wXU/lhUBI3KQ9JzRv/y0yul/8FdZG/TPfpw1MWfPboYkxq4yN5lbxbs8BtRSmP7

Any additional comments?

Even though the v-else-if is verbose in adding the && isPresentationPrimary which is not needed logically, I would assume Typescript / vue-tsc to still complain.