NSLayoutContraints applied inconsistently (apparently) on UITableViewController - uitableview

Question

I'm trying to add some kind of overlay menu on a UITableViewController. My first goal is to get a background view to be displayed at the bottom of the screen on a very barren controller. I'm doing this programmatically using the following code in the callback for a bar button, i.e. called after the original layout has occurred:
print("self.tableView.frame=\(self.tableView.frame)")
let settingsView = UIView()
settingsView.translatesAutoresizingMaskIntoConstraints = false
settingsView.backgroundColor = UIColor.cyan.withAlphaComponent(0.5)
self.view.addSubview(settingsView)
self.view.addConstraints([
NSLayoutConstraint(item: settingsView, attribute: .bottom, relatedBy: .equal, toItem: self.tableView, attribute: .bottom, multiplier: 1, constant: 50),
NSLayoutConstraint(item: settingsView, attribute: .leading, relatedBy: .equal, toItem: self.tableView, attribute: .leading, multiplier: 1, constant: 0),
NSLayoutConstraint(item: settingsView, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: self.view.frame.width),
//NSLayoutConstraint(item: settingsView, attribute: .trailing, relatedBy: .equal, toItem: self.tableView, attribute: .trailing, multiplier: 1, constant: 0),
NSLayoutConstraint(item: settingsView, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 100)
])
self.view.setNeedsLayout()
But the result doesn't look like I expected: instead of being at the bottom of the screen, the bottom of my view is actually aligned with the top margin (hence the 50 value to see it poke through, you can see the cyan color through the navigation bar on the picture attached). Why is that? If I change the first constraint to align tops instead of bottoms, it works fine (but at the top of course).
Also, I'm surprised that I have to replace my fourth constraint (the one that is commented out, supposedly to align the right edge of the view with the right edge of the screen) with the third one (which sets the width, but somehow seems less clean). If I use the fourth one, then the view disappears completely (I'm guessing it gets a width of 0). What's the reason for that?
The print command at the beginning ensures that the tableView has the right size:
self.tableView.frame=(0.0, 0.0, 375.0, 667.0)
It all seems trivial enough so there's definitely something I'm not seeing here...

Answer 1

So the issue here really seems to be the UITableView(Controller), since these constraints work fine with a normal UIView(Controller). The UINavigationController around it doesn't play a role here. For some reason, it seems like the .bottom and .trailing anchors can't be used on a table view — if someone knows why or can explain to me how to do it, please do!
Anyway, I've gone around the problem by using the actual measurements of the view, which are correct. So the first constraint becomes:
NSLayoutConstraint(item: settingsView,
attribute: .bottom,
relatedBy: .equal,
toItem: self.view,
attribute: .top,
multiplier: 1,
constant: self.view.frame.height + self.view.bounds.minY)
This brings the view nicely to the bottom of the screen. The self.view.bounds.minY in the constant accounts for the presence of a navigation bar at the top of the screen. Still feels a bit like a "hack" to me, especially because I don't understand why the other version doesn't work.