koher

let a = [[2], [3 ,5]] for var (i, numbers) in a.enumerated() { numbers.append(3) print("\(i): \(numbers)") }

Version:

swift-4.1.1-RELEASE

Output:

0: [2, 3] 1: [3, 5, 3]

Error:

/usercode/main.swift:3:10: warning: variable 'i' was never mutated; consider changing to 'let' constant for var (i, numbers) in a.enumerated() { ^