> On Feb 8, 2017, at 12:18 AM, Jacob Bandes-Storch via swift-dev > <swift-dev@swift.org> wrote: > I don't think it would be a very big parser change to invert the > relationship. Maybe I'll try it out and put up another PR. > > On the other hand, noticed the header comment says: > > /// ...Because the capture list is evaluated outside of the closure, this > /// CaptureList wraps the ClosureExpr. The dynamic semantics are that > evaluates > /// the variable bindings from the capture list, then evaluates the > /// subexpression (the closure itself) and returns the result.
I think the original representation just made the captures part of the ClosureExpr, and IIRC Chris changed it to this intentionally. I don't remember why; maybe it was causing problems for some tooling that wanted to walk the expression tree and find uses of the variable? It's certainly kindof weird for IRGen. John. > > 🤷‍ > > On Tue, Feb 7, 2017 at 9:10 PM, Slava Pestov <spes...@apple.com > <mailto:spes...@apple.com>> wrote: > >> On Feb 7, 2017, at 9:09 PM, Jacob Bandes-Storch <jtban...@gmail.com >> <mailto:jtban...@gmail.com>> wrote: >> >> PR'd: https://github.com/apple/swift/pull/7326 >> <https://github.com/apple/swift/pull/7326> >> >> Although I would also ask: why is CaptureListExpr a parent of ClosureExpr >> and not a child? > > I think it’s kind of arbitrary. You could also argue that they should be one > and the same AST node. I think right now it’s just a property of how the > parser works, the capture list comes first, before the closure body? > > Slava > >> >> Jacob >> >> On Tue, Feb 7, 2017 at 7:56 PM, Slava Pestov <spes...@apple.com >> <mailto:spes...@apple.com>> wrote: >> >>> On Feb 7, 2017, at 7:30 PM, Jacob Bandes-Storch via swift-dev >>> <swift-dev@swift.org <mailto:swift-dev@swift.org>> wrote: >>> >>> I just learned about CaptureListExpr when working on some diagnostics. Is >>> there a particular reason that its member "closureBody" is an Expr* and not >>> a ClosureExpr*? There seems to be only one place it's built >>> <https://github.com/apple/swift/blob/1e46f13184d7256c991b2ba9424af9efe3cd860f/lib/Parse/ParseExpr.cpp#L2425>, >>> and the body is always a ClosureExpr. >>> >>> I can see one minor place >>> <https://github.com/apple/swift/blob/1e46f13184d7256c991b2ba9424af9efe3cd860f/lib/AST/ASTWalker.cpp#L663-L665> >>> where it might be less convenient to have a ClosureExpr, but otherwise >>> there doesn't seem to be much of a reason to keep it generalized to Expr*. >> >> Since autoclosures cannot have capture lists, I think the change you’re >> suggesting makes sense. >> >> Slava >> >>> >>> Jacob >>> _______________________________________________ >>> swift-dev mailing list >>> swift-dev@swift.org <mailto:swift-dev@swift.org> >>> https://lists.swift.org/mailman/listinfo/swift-dev >>> <https://lists.swift.org/mailman/listinfo/swift-dev> >> >> > > > _______________________________________________ > swift-dev mailing list > swift-dev@swift.org > https://lists.swift.org/mailman/listinfo/swift-dev
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