On Mon, Oct 2, 2017 at 22:23 Slava Pestov <spes...@apple.com> wrote: > On Oct 2, 2017, at 8:06 PM, Xiaodi Wu <xiaodi...@gmail.com> wrote: > > On Mon, Oct 2, 2017 at 9:55 PM, Slava Pestov <spes...@apple.com> wrote: > >> >> On Oct 2, 2017, at 7:52 PM, Kelvin Ma <kelvin1...@gmail.com> wrote: >> >> Is this only a problem with fileprivate or does it extend to private >> members too? I feel like this would be a very valuable feature to support. >> >> >> Private members too. Consider this example, >> >> struct S { >> private func f() {} >> } >> >> The member S.f mangles >> as _T06struct1SV1f33_AB643CAAAE0894CD0BC8584D7CA3AD23LLyyF. In this case, I >> suppose we won’t need the private discriminator because there can only be >> one S.f that’s directly a member of S, and not an extension. However >> imagine if two different source files both defined extensions of S, with a >> private member f. You would need to disambiguate them somehow. >> > > The simple-minded way to do this would be to require @_versioned > annotations on private and fileprivate members to supply an internally > unique alternative name to be used for mangling-as-though-internal (i.e. > `@_versioned(my_extension_f)`). Such a function becoming public in an > ABI-compatible way would require renaming the "actual" name to the unique > @_versioned name. > > > We have _silgen_name for that, but we really don’t want to expose this > more generally because people have been abusing it to make things visible > to C, and they should be using @_cdecl instead. >
The difference here would be that the "@_versioned name" would be subject to mangling. It's essentially equivalent to a way of specifying a custom discriminator to be hashed so that the source file name is omitted and not ABI. Not that I think it'd be elegant, but it would not be abusable like _silgen_name. > A more elegant refinement could be to have @_versioned private and > fileprivate members mangled as though internal, erroring if two or more > members with the same name are both @_versioned--would that work? > > > If you’re going to do that what is the value in having the capability at > all? > Solely to have some way of preventing members in one file from calling members in another file at compile time.
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