Xcode "Size to fit contents" disabled

I fixed the issue by dragging around the labels and resizing them (randomly) manually and then the option was enabled!

OK this is one that has bugged me for a while. But I finally figured out that if you tap one of the corner handles of the label (you will briefly see a diagonal line mouse icon for resizing) then the "size to fit contents" option is re-enabled.

This also works for getting the "horizontal rule" and "vertical rule" options back if you tap on one of the corner handles of a view.