When building a module, forward diagnostics to the outer diagnostic consumer.

Previously, we would clone the current diagnostic consumer to produce
a new diagnostic consumer to use when building a module. The problem
here is that we end up losing diagnostics for important diagnostic
consumers, such as serialized diagnostics (where we'd end up with two
diagnostic consumers writing the same output file). With forwarding,
the diagnostics from all of the different modules being built get
forwarded to the one serialized-diagnostic consumer and are emitted in
a sane way.

Fixes <rdar://problem/13663996>.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181067 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/ASTMerge.cpp b/lib/Frontend/ASTMerge.cpp
index bfb3083..b6c644e 100644
--- a/lib/Frontend/ASTMerge.cpp
+++ b/lib/Frontend/ASTMerge.cpp
@@ -34,7 +34,7 @@
 void ASTMergeAction::ExecuteAction() {
   CompilerInstance &CI = getCompilerInstance();
   CI.getDiagnostics().getClient()->BeginSourceFile(
-                                         CI.getASTContext().getLangOpts());
+                                             CI.getASTContext().getLangOpts());
   CI.getDiagnostics().SetArgToStringFn(&FormatASTNodeDiagnosticArgument,
                                        &CI.getASTContext());
   IntrusiveRefCntPtr<DiagnosticIDs>
@@ -42,8 +42,9 @@
   for (unsigned I = 0, N = ASTFiles.size(); I != N; ++I) {
     IntrusiveRefCntPtr<DiagnosticsEngine>
         Diags(new DiagnosticsEngine(DiagIDs, &CI.getDiagnosticOpts(),
-                                    CI.getDiagnostics().getClient(),
-                                    /*ShouldOwnClient=*/false));
+                                    new ForwardingDiagnosticConsumer(
+                                          *CI.getDiagnostics().getClient()),
+                                    /*ShouldOwnClient=*/true));
     ASTUnit *Unit = ASTUnit::LoadFromASTFile(ASTFiles[I], Diags,
                                              CI.getFileSystemOpts(), false);
     if (!Unit)