core Using unions in defineProps in conjunction with withDefaults breaks emits type inference

Vue version

3.5.11

Link to minimal reproduction

https://play.vuejs.org/#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

Steps to reproduce

The SFC Playground is a bit broken because even if you remove withDefaults it still won't be able to infer the type if you hover on the emit with your mouse. So I suggest to copy paste the code locally: vscode will be able to infer the event type once you remove withDefaults.

Alternatively you can try to assign the event to a function which expects a different type and run vue-tsc --build --force. Without withDefaults it will complain about the mismatch:

If you leave withDefaults it won't complain because he thinks the inferred type is any:

What is expected?

Using withDefaults in conjuction with union props shouldn't break emits type inference.

What is actually happening?

Using withDefaults in conjuction with union props breaks emits type inference.

This is without withDefaults:

While this is with withDefaults:

System Info

System:
    OS: Linux 6.10 Arch Linux
    CPU: (16) x64 AMD Ryzen 9 PRO 7940HS w/ Radeon 780M Graphics
    Memory: 26.39 GB / 58.64 GB
    Container: Yes
    Shell: 5.2.37 - /bin/bash
  Binaries:
    Node: 20.17.0 - /run/user/1000/fnm_multishells/57865_1728023771872/bin/node
    Yarn: 4.5.0 - /run/user/1000/fnm_multishells/57865_1728023771872/bin/yarn
    npm: 10.8.2 - /run/user/1000/fnm_multishells/57865_1728023771872/bin/npm
    Watchman: 20240414.112832.0 - /usr/bin/watchman
  Browsers:
    Chromium: 129.0.6668.89
  npmPackages:
    vue: ^3.5.11 => 3.5.11

Any additional comments?

No response

Oct 04 '24 15:10 darkbasic

~~Solution in https://github.com/vuejs/core/issues/12012#issuecomment-2377956415~~

Oct 05 '24 04:10 KazariEX

Workaround: https://github.com/vuejs/core/issues/12012#issuecomment-2452963489

Nov 02 '24 11:11 KazariEX