[swift-evolution] Proposal: Change Obj-C name for nested types to include enclosing types

[Jordan Rose]

I would rather just not print nested types in the generated header. We already don't do so if the enclosing type is not Objective-C-compatible.

Jordan


> On Dec 9, 2015, at 15:24, Kevin Ballard via swift-evolution <swift-evolution at swift.org> wrote:
> 
> When exposing some type to Obj-C, if the type is nested within another type, the Obj-C name should include the enclosing types.
> 
> For example:
> 
> class Foo: NSObject {
>    @objc enum Bar: Int {
>        case One, Two
>    }
>    @objc class Baz: NSObject {}
> }
> 
> is currently exported to Swift as
> 
> SWIFT_CLASS("_TtC7unnamed3Foo")
> @interface Foo : NSObject
> - (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
> @end
> 
> typedef SWIFT_ENUM(NSInteger, Bar) {
>  BarOne = 0,
>  BarTwo = 1,
> };
> 
> SWIFT_CLASS("_TtCC7unnamed3Foo3Baz")
> @interface Baz : NSObject
> - (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
> @end
> 
> I think it should be exported instead as
> 
> SWIFT_CLASS("_TtC7unnamed3Foo")
> @interface Foo : NSObject
> - (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
> @end
> 
> typedef SWIFT_ENUM(NSInteger, FooBar) {
>  FooBarOne = 0,
>  FooBarTwo = 1,
> };
> 
> SWIFT_CLASS("_TtCC7unnamed3Foo3Baz")
> @interface FooBaz : NSObject
> - (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
> @end
> 
> This is because the Obj-C declarations are all at the top level (as Obj-C does not have nested types), so a type that is clearly unambiguous in Swift may become ambiguous in Obj-C. As a trivial example, the following Swift code:
> 
> class Foo: NSObject {
>    @objc enum Bar: Int {
>        case One, Two
>    }
> }
> 
> class Baz: NSObject {
>    @objc enum Bar: Int {
>        case Apple, Orange
>    }
> }
> 
> is currently exported to Obj-C as:
> 
> SWIFT_CLASS("_TtC7unnamed3Baz")
> @interface Baz : NSObject
> - (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
> @end
> 
> typedef SWIFT_ENUM(NSInteger, Bar) {
>  BarApple = 0,
>  BarOrange = 1,
> };
> 
> SWIFT_CLASS("_TtC7unnamed3Foo")
> @interface Foo : NSObject
> - (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
> @end
> 
> typedef SWIFT_ENUM(NSInteger, Bar) {
>  BarOne = 0,
>  BarTwo = 1,
> };
> 
> This is attempting to redefine the type Bar, which is of course problematic.
> 
> -Kevin Ballard
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