Add: Fallible.init(_:error:using:)

[oscbyspro]

I stumbled upon this ceremony while working on composable (#126) algorithms:

func algorithm<T>(_ value: consuming T) -> Fallible<T> {
    var error: Bool = false
    
    value = foo(value).sink(&error)
    value = bar(value).sink(&error)
    value = baz(value).sink(&error)

    return Fallible(value, error: error)
}

It isn't terrible, but a Fallible.sink(_:performing:) is perhaps more ergonomic:

func algorithm<T>(_ value: consuming T) -> Fallible<T> {
    Fallible.sink(consume  value) { 
        value,  error in
        value = foo(value).sink(&error)
        value = bar(value).sink(&error)
        value = baz(value).sink(&error)
    }
}

[oscbyspro]

Having thought about this for some time, I'm leaning in the other direction. I'm not convinced that this is a problem that needs solving. Similarly, the static Fallible.sink(_:) method has not been used much and could be removed. Hm.

[oscbyspro]

I'm working on a mini Fallible<T> rework and this version is perhaps convenient enough:

extension Fallible {
    @inlinable public init<Error>(
        _ value: consuming Value,
        error: consuming Bool = false,
        using  setup: (inout Value, inout Bool) throws(Error) -> Void
    )   throws(Error)
}