duplicates:

• SR-1534 Error: Call is to rethrows function, but a defaulted argument function can throw

Issue Description:

If I write a rethrowing function that takes a possibly throwing closure and provide a non-throwing default value, I have to use 'try' when calling that function without an argument. Is this the right behavior? The compiler should be aware that the default closure doesn't throw, so it would be nice if the "default" function call wasn't marked as rethrowing:

func foo(_ f: () throws -> Void = { print("Hello!") }) rethrows {
    try f()
}

foo({ print("Hey!") })
// Hey!
foo()
// error: call can throw but is not marked with 'try'
// note: call is to 'rethrows' function, but argument function can throw
try foo()
// Hello!