Swift: Assign Optional Operator

AssignOptional.swift

precedencegroup optionalAssignPrecedence {
    associativity: left
    higherThan: AssignmentPrecedence
}

/// If rhs has a value, assigns rhs to lhs
/// If rhs is an empty optional, does nothing
infix operator ?= : optionalAssignPrecedence
func ?=<T: Any>(lhs: inout T, rhs: T?) {
    if let rhs = rhs {
        lhs = rhs
    }
}

Example of usage:

var left = "Before"

let empty: String? = nil
let notEmpty = "After"

left ?= empty // Right side is empty, do nothing
print(left) // Prints "Before"

left ?= notEmpty // Right side has value, assign to left
print(left) // Prints "After"