+1 - Dave Sweeris
> On May 16, 2016, at 4:06 PM, Joe Groff via swift-evolution > <[email protected]> wrote: > > Currently, we parse a type after 'as[?!]' and 'is'. This is mostly what you'd > expect, but does lead to problems when an 'as' expression appears as part of > a comparison: > > 20 as Int64 < y as Int64 // error, '>' expected to close generic > parameter list Int64<y> > > Looking to the future, many people have also expressed interest in the > ability to do dynamic type checks against metatype values, not only static > types, as in: > > class Base {} > class DerivedA {} > class DerivedB {} > > var x: Base.Type = DerivedA > > DerivedA() as? x // succeeds > DerivedB() as? x // fails > > If we accept > https://github.com/apple/swift-evolution/blob/master/proposals/0090-remove-dot-self.md, > dropping the '.self' requirement to refer to type objects, then I think we > should also change 'is' and 'as' to parse the expression grammar on their > right-hand side, leaving it up to the normal expression disambiguation rule > to handle angle brackets. This solves the '20 as Int64 < x' problem, and > prepares us to support dynamic is/as queries in the future. (To be clear, > designing dynamic queries should be its own discussion.) What do you all > think? > > -Joe > _______________________________________________ > swift-evolution mailing list > [email protected] > https://lists.swift.org/mailman/listinfo/swift-evolution _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
