> On Mar 26, 2017, at 01:14, Slava Pestov via swift-users
> <swift-users@swift.org> wrote:
>
> Hi Ray,
>
> There are two overloads of filter() available on ‘array.lazy’; the version
> that takes an escaping closure and returns a LazyFilterCollection, and the
> version that takes a non-escaping closure and returns [Int].
>
> In the first example, we pick the LazyFilterCollection-returning overload,
> because the literal closure { predicate($0) } can be coerced to both an
> escaping or a non-escaping closure type, and in the absence of additional
> constraints we go with the overload from a concrete type over an overload in
> a protocol extension. After the overload has been picked we validate the body
> of the closure, and notice that it is invalid because whole the closure is
> already known to be @escaping, it references the non-@escaping ‘predicate’.
>
> In the second example, ‘predicate’ is known to be non-@escaping, which rules
> out the first overload completely, so we go with the second overload and
> perform a non-lazy filter.
>
> I would argue this is somewhat confusing, but it might be difficult to change
> the overload resolution rules in a way where the first overload is always
> chosen.
It seems like we could just not take escaping-ness into account at all, and
only diagnose if it mismatches. We'd have to decide if we want that behavior,
though.
Jordan
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