Add protocol redefinition to the current scope/context

Not doing so causes the AST writter to assert since the decl in question
never gets emitted. This is fine when modules is not used, but otherwise
we need to serialize something other than garbage.

rdar://problem/39844933

Differential Revision: https://reviews.llvm.org/D47297

llvm-svn: 336031

clang/lib/Sema/SemaDeclObjC.cpp

@@ -1210,6 +1210,11 @@ Sema::ActOnStartProtocolInterface(SourceLocation AtProtoInterfaceLoc,
     PDecl = ObjCProtocolDecl::Create(Context, CurContext, ProtocolName,
                                      ProtocolLoc, AtProtoInterfaceLoc,
                                      /*PrevDecl=*/nullptr);
+
+    // If we are using modules, add the decl to the context in order to
+    // serialize something meaningful.
+    if (getLangOpts().Modules)
+      PushOnScopeChains(PDecl, TUScope);
     PDecl->startDefinition();
   } else {
     if (PrevDecl) {

clang/test/Modules/Inputs/protocol-redefinition/Base.framework/Headers/Base.h

@@ -0,0 +1,3 @@
+@protocol Foo
+- (void)someMethodOnFoo;
+@end

clang/test/Modules/Inputs/protocol-redefinition/Base.framework/Modules/module.modulemap

@@ -0,0 +1,4 @@
+framework module Base {
+  header "Base.h"
+  export *
+}

clang/test/Modules/Inputs/protocol-redefinition/Kit.framework/Headers/Kit.h

@@ -0,0 +1,6 @@
+#import <Base/Base.h>
+
+// REDECLARATION
+@protocol Foo
+- (void)someMethodOnFoo;
+@end

clang/test/Modules/Inputs/protocol-redefinition/Kit.framework/Modules/module.modulemap

@@ -0,0 +1,4 @@
+framework module Kit {
+  header "Kit.h"
+  export *
+}

clang/test/Modules/protocol-redefinition.m

@@ -0,0 +1,6 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -F%S/Inputs/protocol-redefinition -fsyntax-only %s -Wno-private-module -verify
+
+// expected-no-diagnostics
+
+@import Kit;