Swift extension that allows moving between a single index and another index in a mutable collection

MutableCollection+Move.swift

//  The MIT License (MIT)
//
//  Copyright © 2018 Tony Arnold (@tonyarnold)
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.
// 
//  Thanks to Ben Cohen (@AirspeedSwift) for the guidance on making an 
//  unconstrained version of this method.

extension MutableCollection {
    /// Moves the item at the source index to be positioned before the item at the given target index.
    ///
    /// - Parameters:
    ///   - from: The position of the element to move. `from` must be a valid index of the array.
    ///   - to: The position to move the new element to. `to` must be a valid index of the array or equal to its `endIndex` property.
    mutating func move2(from: Index, to: Index) {
        if from < to {
            var i = from
            var j = index(after: i)
            while j != to {
                swapAt(i, j)
                i = j
                formIndex(after: &j)
            }
        } else {
            var i = to
            while i != from {
                swapAt(i, from)
                formIndex(after: &i)
            }
        }
    }
}