 @discardableResult
 public func - (left: SteviaLeftFlexibleMargin, right: UIView) -> UIView {
     if let spv = right.superview {
-        let c = constraint(item: right, attribute: .left,
+        let c = constraint(item: right, attribute: .leading,
                            relatedBy: left.fm.relation, toItem: spv,
-                           attribute: .left,
+                           attribute: .leading,
                            constant: left.fm.points)
         spv.addConstraint(c)
     }

public func - (left: PartialFlexibleConstraint, right: UIView) -> [UIView] {
    if let views = left.views {
        if let spv = right.superview {
            let c = constraint(item: right, attribute: .left,
                               relatedBy: left.fm.relation, toItem: views.last,
                               attribute: .right,
                               constant: left.fm.points)
            spv.addConstraint(c)
        }
        return views + [right]
    } else {
        if let spv = right.superview {
            let c = constraint(item: right, attribute: .left,
                               relatedBy: left.fm.relation, toItem: left.view1!,
                               attribute: .right,
                               constant: left.fm.points)
            spv.addConstraint(c)
        }

@discardableResult
public func - (left: UIView, right: SteviaRightFlexibleMargin) -> UIView {
    if let spv = left.superview {
        let c = constraint(item: spv, attribute: .trailing,
                           relatedBy: right.fm.relation, toItem: left,
                           attribute: .trailing,
                           constant: right.fm.points)
        spv.addConstraint(c)
    }
