// A function that demonstrates this issue.
func apply<Value>(_ value: Value, _ transform: (inout Value) -> Void) -> Value {
    var value = value
    transform(&value)
    return value
}

// This code works as expected.
func testOne() -> [Int] {
    return apply([1, 2, 3], {
        $0.append(4)
    })
}

// This code works as expected.
let testTwo = apply([1, 2, 3], { (array: inout [Int]) -> Void in
    array.append(4)
})

// This code fails to compile because the "type of expression is ambiguous
// without more context". After further investigation the type appears to be
// ambiguous because the closure provided does not necessarily have an inout
// parameter (even though that is specified in the signature of apply).
let testThree = apply([1, 2, 3], {
    $0.append(4)
})

// This code also fails but for different reasons. I expected it to work because
// testOne compiles without issue. It does not result in an error with a
// diagnostic and source location but instead says "parameters may not have
// the 'var' specifier".
let testFour: [Int] = apply([1, 2, 3], {
    $0.append(4)
})