6 files changed, 14 insertions, 5 deletions
diff --git a/clang/lib/Basic/DiagnosticIDs.cpp b/clang/lib/Basic/DiagnosticIDs.cpp
index efc3f94c959..3c370f67fa3 100644
--- a/clang/lib/Basic/DiagnosticIDs.cpp
+++ b/clang/lib/Basic/DiagnosticIDs.cpp
@@ -351,7 +351,7 @@ bool DiagnosticIDs::isDefaultMappingAsError(unsigned DiagID) {
   if (DiagID >= diag::DIAG_UPPER_LIMIT)
     return false;
 
-  return GetDefaultDiagMapping(DiagID).getSeverity() == diag::Severity::Error;
+  return GetDefaultDiagMapping(DiagID).getSeverity() >= diag::Severity::Error;
 }
 
 /// getDescription - Given a diagnostic ID, return a description of the
diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 635d566159b..e0bf1c51c85 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -2509,7 +2509,8 @@ static bool serializeUnit(ASTWriter &Writer,
 }
 
 bool ASTUnit::serialize(raw_ostream &OS) {
-  bool hasErrors = getDiagnostics().hasErrorOccurred();
+  // For serialization we are lenient if the errors were only warn-as-error kind.
+  bool hasErrors = getDiagnostics().hasUncompilableErrorOccurred();
 
   if (WriterData)
     return serializeUnit(WriterData->Writer, WriterData->Buffer,
diff --git a/clang/lib/Frontend/ChainedIncludesSource.cpp b/clang/lib/Frontend/ChainedIncludesSource.cpp
index 1c1081fbe08..51771bfb549 100644
--- a/clang/lib/Frontend/ChainedIncludesSource.cpp
+++ b/clang/lib/Frontend/ChainedIncludesSource.cpp
@@ -164,7 +164,7 @@ IntrusiveRefCntPtr<ExternalSemaSource> clang::createChainedIncludesSource(
     ArrayRef<llvm::IntrusiveRefCntPtr<ModuleFileExtension>> Extensions;
     auto consumer = llvm::make_unique<PCHGenerator>(
         Clang->getPreprocessor(), "-", nullptr, /*isysroot=*/"", Buffer,
-        Extensions);
+        Extensions, /*AllowASTWithErrors=*/true);
     Clang->getASTContext().setASTMutationListener(
                                             consumer->GetASTMutationListener());
     Clang->setASTConsumer(std::move(consumer));
diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index a43513530e7..67762bde343 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -1897,7 +1897,7 @@ AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
   if (cast<DeclContext>(D)->isDependentContext())
     return;
 
-  if (Diags.hasUncompilableErrorOccurred() || Diags.hasFatalErrorOccurred()) {
+  if (Diags.hasUncompilableErrorOccurred()) {
     // Flush out any possibly unreachable diagnostics.
     flushDiagnostics(S, fscope);
     return;
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 820f339a75d..b35bd7bd329 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -2309,6 +2309,11 @@ ASTReader::ReadControlBlock(ModuleFile &F,
         Diag(diag::err_pch_with_compiler_errors);
         return HadErrors;
       }
+      if (hasErrors) {
+        Diags.ErrorOccurred = true;
+        Diags.UncompilableErrorOccurred = true;
+        Diags.UnrecoverableErrorOccurred = true;
+      }
 
       F.RelocatablePCH = Record[4];
       // Relative paths in a relocatable PCH are relative to our sysroot.
diff --git a/clang/lib/Serialization/GeneratePCH.cpp b/clang/lib/Serialization/GeneratePCH.cpp
index 4a2255ab6d3..308fde8b1dd 100644
--- a/clang/lib/Serialization/GeneratePCH.cpp
+++ b/clang/lib/Serialization/GeneratePCH.cpp
@@ -51,7 +51,10 @@ void PCHGenerator::HandleTranslationUnit(ASTContext &Ctx) {
   // Emit the PCH file to the Buffer.
   assert(SemaPtr && "No Sema?");
   Buffer->Signature =
-      Writer.WriteAST(*SemaPtr, OutputFile, Module, isysroot, hasErrors);
+      Writer.WriteAST(*SemaPtr, OutputFile, Module, isysroot,
+                      // For serialization we are lenient if the errors were
+                      // only warn-as-error kind.
+                      PP.getDiagnostics().hasUncompilableErrorOccurred());
 
   Buffer->IsComplete = true;
 }