'GetOrSet' accessors for optionals and dictionaries

GetOrSet.swift

import Foundation

public extension Optional {
    mutating func getOrSet(builder: () -> Wrapped) -> Wrapped {
        switch self {
        case .some(let wrapped):
            return wrapped
        case .none:
            let value = builder()
            self = .some(value)
            return value
        }
    }
}

public extension Dictionary {
    mutating func getOrSet(key: Key, builder: () -> Value) -> Value {
        self[key] ?? {
            let value = builder()
            self[key] = value
            return value
        }()
    }
}