[swift-dev] Why doesn't CaptureListExpr hold a ClosureExpr?

[Slava Pestov]

> On Feb 7, 2017, at 9:09 PM, Jacob Bandes-Storch <jtbandes at 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 <spestov at apple.com <mailto:spestov at apple.com>> wrote:
> 
>> On Feb 7, 2017, at 7:30 PM, Jacob Bandes-Storch via swift-dev <swift-dev at swift.org <mailto:swift-dev at 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
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