[PATCH] D49462: [ObjC] Error out when using forward-declared protocol in a @protocol expression

[John McCall via Phabricator via cfe-commits]

rjmccall accepted this revision.
rjmccall added a comment.
This revision is now accepted and ready to land.

LGTM.



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Comment at: lib/CodeGen/CGObjCMac.cpp:6788
+         "emitting protocol metadata without definition");
+  PD = PD->getDefinition();
 
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arphaman wrote:
> rjmccall wrote:
> > What happens in the `@implementation` case (the one that we're not diagnosing yet) when the protocol is a forward declaration?
> We emit an `external global` reference to the protocol metadata using `GetOrEmitProtocolRef`, so this assertion won't be triggered until we force the emission of protocol metadata from implementation as planned in a follow-up patch.
Okay.  I mean, that's also unfortunate behavior, since protocol descriptors are basically `linkonce` and should be emitted in every translation unit that uses them, but I agree it's less damaging than the behavior for `@protocol`, and it means this assertion is safe.


Repository:
  rC Clang

https://reviews.llvm.org/D49462