throwing closure parameter results in different resolution

ambiguous.swift

class A {}

// foo

func foo<T>(_ v: T, handler: () -> Void) -> T {
    print("regular")
    return v
}

func foo<T>(_ v: T?, handler: () throws -> Void) rethrows -> T? {
    print("optional")
    return v
}

// bar

func bar<T>(_ v: T, handler: () -> Void) -> T {
    print("regular")
    return v
}

func bar<T>(_ v: T?, handler: () -> Void) -> T? {
    print("optional")
    return v
}

let result1: A? = foo(A(), handler: {}) // error: ambiguous use of 'foo(_:handler:)'
let result2: A? = bar(A(), handler: {}) // ok, "optional"