# Test if a type conforms to a non-existential protocol

**URL:** <https://forums.swift.org/t/test-if-a-type-conforms-to-a-non-existential-protocol/35479>\
**Category:** Pitches\
**Created:** [April 18, 2020, 2:44pm UTC](https://forums.swift.org/t/test-if-a-type-conforms-to-a-non-existential-protocol/35479 "2020-04-18T14:44:46Z")\
**Posts on this page:** 1\
**Showing post:** 53

<div class="post-metadata">

**Author:** ![Jumhyn](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/jumhyn/32/3891_2.png) [@Jumhyn](https://forums.swift.org/u/Jumhyn)\
**Post date:** [May 14, 2020, 10:04pm UTC](https://forums.swift.org/t/test-if-a-type-conforms-to-a-non-existential-protocol/35479/53 "2020-05-14T22:04:56Z")

</div>

> [@anandabits](#):
>
> I noticed `@_implementationOnly` in your code. I haven't run into that before. I can guess what it might do, but would like to understand it better. Can you explain or point me in the right direction to learn more?

Not @Nevin, but the relevant thread is [here](https://forums.swift.org/t/update-on-implementation-only-imports/26996)! 🙂

---

_[View the full topic](https://forums.swift.org/t/test-if-a-type-conforms-to-a-non-existential-protocol/35479)._