Auto Layout issues: a few items are ambiguous

[hipwelljo]

• I've read and understood the Contributing guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've searched for any related issues and avoided creating a duplicate issue.

Description

If you run the example app and check out the View Debugger you'll see there's a few Auto Layout issues:

• Vertical position is ambiguous for UIButton
• Width and horizontal position are ambiguous for MessageTextView
• Height and vertical position are ambiguous for UIView

Reproducible in:

• This is reproducible in the sample project.
  SlackTextViewController version:
  iOS version(s): iOS 11.0
  Device(s): iPhone 8

Attachments: