Index: clang/include/clang/Serialization/ASTReader.h
===================================================================
--- clang/include/clang/Serialization/ASTReader.h
+++ clang/include/clang/Serialization/ASTReader.h
@@ -1450,8 +1450,6 @@
   void Error(StringRef Msg) const;
   void Error(unsigned DiagID, StringRef Arg1 = StringRef(),
              StringRef Arg2 = StringRef(), StringRef Arg3 = StringRef()) const;
-  void Error(unsigned DiagID, StringRef Arg1, StringRef Arg2,
-             unsigned Select) const;
   void Error(llvm::Error &&Err) const;
 
 public:
Index: clang/lib/Serialization/ASTReader.cpp
===================================================================
--- clang/lib/Serialization/ASTReader.cpp
+++ clang/lib/Serialization/ASTReader.cpp
@@ -1246,12 +1246,6 @@
     Diag(DiagID) << Arg1 << Arg2 << Arg3;
 }
 
-void ASTReader::Error(unsigned DiagID, StringRef Arg1, StringRef Arg2,
-                      unsigned Select) const {
-  if (!Diags.isDiagnosticInFlight())
-    Diag(DiagID) << Arg1 << Arg2 << Select;
-}
-
 void ASTReader::Error(llvm::Error &&Err) const {
   Error(toString(std::move(Err)));
 }
@@ -2395,7 +2389,7 @@
   auto FileChange = HasInputFileChanged();
   // For an overridden file, there is nothing to validate.
   if (!Overridden && FileChange != ModificationType::None) {
-    if (Complain) {
+    if (Complain && !Diags.isDiagnosticInFlight()) {
       // Build a list of the PCH imports that got us here (in reverse).
       SmallVector<ModuleFile *, 4> ImportStack(1, &F);
       while (!ImportStack.back()->ImportedBy.empty())
@@ -2406,17 +2400,17 @@
       unsigned DiagnosticKind =
           moduleKindForDiagnostic(ImportStack.back()->Kind);
       if (DiagnosticKind == 0)
-        Error(diag::err_fe_pch_file_modified, Filename, TopLevelPCHName,
-              (unsigned)FileChange);
+        Diag(diag::err_fe_pch_file_modified)
+            << Filename << TopLevelPCHName << FileChange;
       else if (DiagnosticKind == 1)
-        Error(diag::err_fe_module_file_modified, Filename, TopLevelPCHName,
-              (unsigned)FileChange);
+        Diag(diag::err_fe_module_file_modified)
+            << Filename << TopLevelPCHName << FileChange;
       else
-        Error(diag::err_fe_ast_file_modified, Filename, TopLevelPCHName,
-              (unsigned)FileChange);
+        Diag(diag::err_fe_ast_file_modified)
+            << Filename << TopLevelPCHName << FileChange;
 
       // Print the import stack.
-      if (ImportStack.size() > 1 && !Diags.isDiagnosticInFlight()) {
+      if (ImportStack.size() > 1) {
         Diag(diag::note_pch_required_by)
           << Filename << ImportStack[0]->FileName;
         for (unsigned I = 1; I < ImportStack.size(); ++I)
@@ -2424,8 +2418,7 @@
             << ImportStack[I-1]->FileName << ImportStack[I]->FileName;
       }
 
-      if (!Diags.isDiagnosticInFlight())
-        Diag(diag::note_pch_rebuild_required) << TopLevelPCHName;
+      Diag(diag::note_pch_rebuild_required) << TopLevelPCHName;
     }
 
     IsOutOfDate = true;