Jordan Rose e575d2d5ba [ClangImporter] Error structs from enums are not imported decls. ...

Enums with the ns_error_domain attribute represent codes for NSError,
which means Swift developers will expect to interact with them in
terms of Error. SE-0112 improved bridging for these enums to generate
a struct with the following form:

    struct MyError: Error {
      @objc enum Code: RawRepresentable {
        case outOfMemory
        case fileNotFound
      }
      var userInfo: [NSObject: AnyObject] { get }
      static var outOfMemory: Code { get }
      static var fileNotFound: Code { get }
    }

where MyError.Code corresponds to the original MyError enum defined in
Objective-C. Until recently, both the enum and the synthesized struct
were marked as having the original enum as their "Clang node", but
that leads to problems: the struct isn't really ObjC-compatible, and
the two decls have the same USR. (The latter had already been worked
around.)

This commit changes the struct to be merely considered a synthesized
"external definition", with no associated Clang node. This meant
auditing everywhere that's looking for a Clang node and seeing which
ones applied to external definitions in general.

There is one regression in quality here: the generated struct is no
longer printed as part of the Swift interface for a header file, since
it's not actually a decl with a corresponding Clang node. The previous
change to AST printing mitigates this a little by at least indicating
that the enum has become a nested "Code" type.

2017-04-24 09:57:41 -07:00

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