Ambiguous height

Question

Using Xcode 8.0 (8A218a)

I get "Ambiguous Height". although (in my opinion) I have limitations on the y axis.

Both of the two subzones within the view have a height (one has a height as a constraint, and one as the size of the content within itself).

See the image below for what it says "Debug View Hierarchy".

Constraints are created in code with the following code:

label UILabel , underscore UIView

 label.translatesAutoresizingMaskIntoConstraints = false underline.translatesAutoresizingMaskIntoConstraints = false addSubview(label) addSubview(underline) label.topAnchor.constraint(equalTo: topAnchor).isActive = true label.leftAnchor.constraint(equalTo: leftAnchor).isActive = true label.rightAnchor.constraint(equalTo: rightAnchor).isActive = true label.bottomAnchor.constraint(equalTo: underline.topAnchor, constant: -5).isActive = true underline.leftAnchor.constraint(equalTo: leftAnchor).isActive = true underline.rightAnchor.constraint(equalTo: rightAnchor).isActive = true underline.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true underline.heightAnchor.constraint(equalToConstant: 2.0).isActive = true 

Here's an example project extracted from a problematic project: https://github.com/everlof/LayoutIssue