> On Sep 25, 2017, at 1:04 PM, David Zarzycki <d...@znu.io> wrote: > > > >> On Sep 25, 2017, at 14:37, Joe Groff <jgr...@apple.com> wrote: >> >> >> >>> On Sep 23, 2017, at 10:36 PM, Robert Widmann via swift-dev >>> <swift-dev@swift.org> wrote: >>> >>> Why is the arrow carrying the “Has Value Semantics Bit” rather than it >>> being part of a protocol composition on an argument type, or a convention >>> bit on the parameter like ‘inout’? >> >> Value semantics is a property of operations, not really of types. I would >> say the function arrow is the right place for it, since not-value-semantics >> propagates in the same manner as an effect like "throws". Dave, you might in >> fact look at how 'throws' type checking is implemented as a model for what >> you're trying to do. > > Hi Joe, > > In fact, I tried to replicate the “closureCanThrow()” logic before emailing > this list, but that didn’t work due to a chicken-and-egg problem that arrises > between when a ClosureExpr's body is type checked and knowing the type of the > ClosureExpr. In other words, a closure has value semantics iff all operations > within it have value semantics. > > As I wrote earlier in this email thread, the “value semantics” implementation > I’m working on is sufficient for the research that I’m doing. That being > said, I took some shortcuts to get it working and the closure type shortcut > bothered me the most. That is why I emailed this list about how to propagate > the contextual ExtInfo bit onto the closure type. Based on John’s helpful > email, I think I’ll just live with the shortcuts I made for now.
If you have something working well enough for your prototype, then great. If you do decide to look at this again, I think it might be easier to flip the polarity of the check—a closure is not-value-semantics if it does anything that's not-value-semantics—which should make it the exact same kind of problem as `throws` propagation. -Joe _______________________________________________ swift-dev mailing list swift-dev@swift.org https://lists.swift.org/mailman/listinfo/swift-dev
