Index: lld/COFF/PDB.cpp
===================================================================
--- lld/COFF/PDB.cpp
+++ lld/COFF/PDB.cpp
@@ -96,8 +96,8 @@
     msf::StreamReader Reader(Stream);
     if (auto EC = Reader.readArray(Types, Reader.getLength()))
       fatal(EC, "Reader::readArray failed");
-    if (!codeview::mergeTypeStreams(Builder, Types))
-      fatal("codeview::mergeTypeStreams failed");
+    if (auto Err = codeview::mergeTypeStreams(Builder, Types))
+      fatal(Err, "codeview::mergeTypeStreams failed");
   }
 
   // Construct section contents.
Index: llvm/include/llvm/DebugInfo/CodeView/TypeStreamMerger.h
===================================================================
--- llvm/include/llvm/DebugInfo/CodeView/TypeStreamMerger.h
+++ llvm/include/llvm/DebugInfo/CodeView/TypeStreamMerger.h
@@ -13,12 +13,13 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/DebugInfo/CodeView/TypeTableBuilder.h"
+#include "llvm/Support/Error.h"
 
 namespace llvm {
 namespace codeview {
 
 /// Merges one type stream into another. Returns true on success.
-bool mergeTypeStreams(TypeTableBuilder &DestStream, const CVTypeArray &Types);
+Error mergeTypeStreams(TypeTableBuilder &DestStream, const CVTypeArray &Types);
 
 } // end namespace codeview
 } // end namespace llvm
Index: llvm/lib/DebugInfo/CodeView/TypeStreamMerger.cpp
===================================================================
--- llvm/lib/DebugInfo/CodeView/TypeStreamMerger.cpp
+++ llvm/lib/DebugInfo/CodeView/TypeStreamMerger.cpp
@@ -56,7 +56,10 @@
 public:
   TypeStreamMerger(TypeTableBuilder &DestStream)
       : DestStream(DestStream), FieldListBuilder(DestStream) {
-    assert(!hadError());
+    // The initial value of LastError have no significance,
+    // but we still need to set its internal "isChecked" flag.
+    // Otherwise it will raise a runtime error. So we do that here.
+    (void)static_cast<bool>(LastError);
   }
 
 /// TypeVisitorCallbacks overrides.
@@ -74,12 +77,15 @@
   Error visitTypeEnd(CVType &Record) override;
   Error visitMemberEnd(CVMemberRecord &Record) override;
 
-  bool mergeStream(const CVTypeArray &Types);
+  Error mergeStream(const CVTypeArray &Types);
 
 private:
   template <typename RecordType>
   Error visitKnownRecordImpl(RecordType &Record) {
-    FoundBadTypeIndex |= !Record.remapTypeIndices(IndexMap);
+    if (!Record.remapTypeIndices(IndexMap))
+      LastError = joinErrors(
+          std::move(LastError),
+          llvm::make_error<CodeViewError>(cv_error_code::corrupt_record));
     IndexMap.push_back(DestStream.writeKnownType(Record));
     return Error::success();
   }
@@ -94,14 +100,15 @@
 
   template <typename RecordType>
   Error visitKnownMemberRecordImpl(RecordType &Record) {
-    FoundBadTypeIndex |= !Record.remapTypeIndices(IndexMap);
+    if (!Record.remapTypeIndices(IndexMap))
+      LastError = joinErrors(
+          std::move(LastError),
+          llvm::make_error<CodeViewError>(cv_error_code::corrupt_record));
     FieldListBuilder.writeMemberType(Record);
     return Error::success();
   }
 
-  bool hadError() { return FoundBadTypeIndex; }
-
-  bool FoundBadTypeIndex = false;
+  Error LastError = Error::success();
 
   BumpPtrAllocator Allocator;
 
@@ -163,9 +170,10 @@
   return llvm::make_error<CodeViewError>(cv_error_code::corrupt_record);
 }
 
-bool TypeStreamMerger::mergeStream(const CVTypeArray &Types) {
+Error TypeStreamMerger::mergeStream(const CVTypeArray &Types) {
   assert(IndexMap.empty());
   TypeVisitorCallbackPipeline Pipeline;
+  LastError = Error::success();
 
   TypeDeserializer Deserializer;
   Pipeline.addCallbackToPipeline(Deserializer);
@@ -173,15 +181,14 @@
 
   CVTypeVisitor Visitor(Pipeline);
 
-  if (auto EC = Visitor.visitTypeStream(Types)) {
-    consumeError(std::move(EC));
-    return false;
-  }
+  if (auto EC = Visitor.visitTypeStream(Types))
+    return EC;
   IndexMap.clear();
-  return !hadError();
+
+  return std::move(LastError);
 }
 
-bool llvm::codeview::mergeTypeStreams(TypeTableBuilder &DestStream,
-                                      const CVTypeArray &Types) {
+Error llvm::codeview::mergeTypeStreams(TypeTableBuilder &DestStream,
+                                       const CVTypeArray &Types) {
   return TypeStreamMerger(DestStream).mergeStream(Types);
 }