[NFC] Explicitly pass a VFS when creating DiagnosticsEngine (#115852)

Starting with 41e3919ded78d8870f7c95e9181c7f7e29aa3cc4 DiagnosticsEngine
creation might perform IO. It was implicitly defaulting to
getRealFileSystem. This patch makes it explicit by pushing the decision
making to callers.

It uses ambient VFS if one is available, and keeps using
`getRealFileSystem` if there aren't any VFS.

22 files changed, 85 insertions, 60 deletions

diff --git a/clang/unittests/AST/ExternalASTSourceTest.cpp b/clang/unittests/AST/ExternalASTSourceTest.cpp
index 8b70be6..8e1bde1 100644
--- a/clang/unittests/AST/ExternalASTSourceTest.cpp
+++ b/clang/unittests/AST/ExternalASTSourceTest.cpp
@@ -10,13 +10,14 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/AST/ExternalASTSource.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
-#include "clang/AST/ExternalASTSource.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/CompilerInvocation.h"
 #include "clang/Frontend/FrontendActions.h"
 #include "clang/Lex/PreprocessorOptions.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "gtest/gtest.h"
 
 using namespace clang;
@@ -46,7 +47,7 @@ private:
 bool testExternalASTSource(ExternalASTSource *Source,
                            StringRef FileContents) {
   CompilerInstance Compiler;
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   auto Invocation = std::make_shared<CompilerInvocation>();
   Invocation->getPreprocessorOpts().addRemappedFile(
diff --git a/clang/unittests/CodeGen/TestCompiler.h b/clang/unittests/CodeGen/TestCompiler.h
index 891489c..931c75ef 100644
--- a/clang/unittests/CodeGen/TestCompiler.h
+++ b/clang/unittests/CodeGen/TestCompiler.h
@@ -20,6 +20,7 @@
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/TargetParser/Host.h"
 
 namespace llvm {
@@ -35,7 +36,7 @@ struct TestCompiler {
                clang::CodeGenOptions CGO = clang::CodeGenOptions()) {
     compiler.getLangOpts() = LO;
     compiler.getCodeGenOpts() = CGO;
-    compiler.createDiagnostics();
+    compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
     std::string TrStr = llvm::Triple::normalize(llvm::sys::getProcessTriple());
     llvm::Triple Tr(TrStr);
diff --git a/clang/unittests/Driver/DXCModeTest.cpp b/clang/unittests/Driver/DXCModeTest.cpp
index 2a079a6..616c07c 100644
--- a/clang/unittests/Driver/DXCModeTest.cpp
+++ b/clang/unittests/Driver/DXCModeTest.cpp
@@ -219,7 +219,8 @@ TEST(DxcModeTest, DefaultEntry) {
   const char *Args[] = {"clang", "--driver-mode=dxc", "-Tcs_6_7", "foo.hlsl"};
 
   IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-      CompilerInstance::createDiagnostics(new DiagnosticOptions());
+      CompilerInstance::createDiagnostics(*InMemoryFileSystem,
+                                          new DiagnosticOptions());
 
   CreateInvocationOptions CIOpts;
   CIOpts.Diags = Diags;
diff --git a/clang/unittests/Driver/ToolChainTest.cpp b/clang/unittests/Driver/ToolChainTest.cpp
index 8542a16..0787e7d 100644
--- a/clang/unittests/Driver/ToolChainTest.cpp
+++ b/clang/unittests/Driver/ToolChainTest.cpp
@@ -577,7 +577,7 @@ TEST(CompilerInvocation, SplitSwarfSingleCrash) {
 
 TEST(ToolChainTest, UEFICallingConventionTest) {
   clang::CompilerInstance compiler;
-  compiler.createDiagnostics();
+  compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   std::string TrStr = "x86_64-unknown-uefi";
   llvm::Triple Tr(TrStr);
diff --git a/clang/unittests/Frontend/ASTUnitTest.cpp b/clang/unittests/Frontend/ASTUnitTest.cpp
index bd5d5d0..e6524a0 100644
--- a/clang/unittests/Frontend/ASTUnitTest.cpp
+++ b/clang/unittests/Frontend/ASTUnitTest.cpp
@@ -17,6 +17,7 @@
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/ToolOutputFile.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -41,17 +42,18 @@ protected:
 
     const char *Args[] = {"clang", "-xc++", InputFileName.c_str()};
 
-    Diags = CompilerInstance::createDiagnostics(new DiagnosticOptions());
+    auto VFS = llvm::vfs::getRealFileSystem();
+    Diags = CompilerInstance::createDiagnostics(*VFS, new DiagnosticOptions());
 
     CreateInvocationOptions CIOpts;
     CIOpts.Diags = Diags;
+    CIOpts.VFS = VFS;
     CInvok = createInvocation(Args, std::move(CIOpts));
 
     if (!CInvok)
       return nullptr;
 
-    FileManager *FileMgr =
-        new FileManager(FileSystemOptions(), vfs::getRealFileSystem());
+    FileManager *FileMgr = new FileManager(FileSystemOptions(), VFS);
     PCHContainerOps = std::make_shared<PCHContainerOperations>();
 
     return ASTUnit::LoadFromCompilerInvocation(
@@ -134,7 +136,8 @@ TEST_F(ASTUnitTest, ModuleTextualHeader) {
 
   const char *Args[] = {"clang", "test.cpp", "-fmodule-map-file=m.modulemap",
                         "-fmodule-name=M"};
-  Diags = CompilerInstance::createDiagnostics(new DiagnosticOptions());
+  Diags =
+      CompilerInstance::createDiagnostics(*InMemoryFs, new DiagnosticOptions());
   CreateInvocationOptions CIOpts;
   CIOpts.Diags = Diags;
   CInvok = createInvocation(Args, std::move(CIOpts));
@@ -162,7 +165,8 @@ TEST_F(ASTUnitTest, LoadFromCommandLineEarlyError) {
 
   const char *Args[] = {"clang", "-target", "foobar", InputFileName.c_str()};
 
-  auto Diags = CompilerInstance::createDiagnostics(new DiagnosticOptions());
+  auto Diags = CompilerInstance::createDiagnostics(
+      *llvm::vfs::getRealFileSystem(), new DiagnosticOptions());
   auto PCHContainerOps = std::make_shared<PCHContainerOperations>();
   std::unique_ptr<clang::ASTUnit> ErrUnit;
 
@@ -189,7 +193,8 @@ TEST_F(ASTUnitTest, LoadFromCommandLineWorkingDirectory) {
   const char *Args[] = {"clang", "-working-directory", WorkingDir.c_str(),
                         InputFileName.c_str()};
 
-  auto Diags = CompilerInstance::createDiagnostics(new DiagnosticOptions());
+  auto Diags = CompilerInstance::createDiagnostics(
+      *llvm::vfs::getRealFileSystem(), new DiagnosticOptions());
   auto PCHContainerOps = std::make_shared<PCHContainerOperations>();
   std::unique_ptr<clang::ASTUnit> ErrUnit;
 
diff --git a/clang/unittests/Frontend/CodeGenActionTest.cpp b/clang/unittests/Frontend/CodeGenActionTest.cpp
index a6520910..d855302 100644
--- a/clang/unittests/Frontend/CodeGenActionTest.cpp
+++ b/clang/unittests/Frontend/CodeGenActionTest.cpp
@@ -16,6 +16,7 @@
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Lex/PreprocessorOptions.h"
 #include "llvm/Support/FormatVariadic.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -52,7 +53,7 @@ TEST(CodeGenTest, TestNullCodeGen) {
   Invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance Compiler;
   Compiler.setInvocation(std::move(Invocation));
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
   EXPECT_TRUE(Compiler.hasDiagnostics());
 
   std::unique_ptr<FrontendAction> Act(new NullCodeGenAction);
@@ -70,7 +71,7 @@ TEST(CodeGenTest, CodeGenFromIRMemBuffer) {
   Invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance Compiler;
   Compiler.setInvocation(std::move(Invocation));
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
   EXPECT_TRUE(Compiler.hasDiagnostics());
 
   EmitLLVMOnlyAction Action;
@@ -101,7 +102,7 @@ TEST(CodeGenTest, DebugInfoCWDCodeGen) {
   SmallString<256> IRBuffer;
   Compiler.setOutputStream(std::make_unique<raw_svector_ostream>(IRBuffer));
   Compiler.setInvocation(std::move(Invocation));
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*VFS);
   Compiler.createFileManager(std::move(VFS));
 
   EmitLLVMAction Action;
diff --git a/clang/unittests/Frontend/CompilerInstanceTest.cpp b/clang/unittests/Frontend/CompilerInstanceTest.cpp
index 5cf548e9..07329eb2 100644
--- a/clang/unittests/Frontend/CompilerInstanceTest.cpp
+++ b/clang/unittests/Frontend/CompilerInstanceTest.cpp
@@ -13,6 +13,7 @@
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/ToolOutputFile.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -53,7 +54,8 @@ TEST(CompilerInstance, DefaultVFSOverlayFromInvocation) {
   const char *Args[] = {"clang", VFSArg.c_str(), "-xc++", "-"};
 
   IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-      CompilerInstance::createDiagnostics(new DiagnosticOptions());
+      CompilerInstance::createDiagnostics(*llvm::vfs::getRealFileSystem(),
+                                          new DiagnosticOptions());
 
   CreateInvocationOptions CIOpts;
   CIOpts.Diags = Diags;
@@ -87,8 +89,9 @@ TEST(CompilerInstance, AllowDiagnosticLogWithUnownedDiagnosticConsumer) {
   auto DiagPrinter = std::make_unique<TextDiagnosticPrinter>(
       DiagnosticsOS, new DiagnosticOptions());
   CompilerInstance Instance;
-  IntrusiveRefCntPtr<DiagnosticsEngine> Diags = Instance.createDiagnostics(
-      DiagOpts, DiagPrinter.get(), /*ShouldOwnClient=*/false);
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+      Instance.createDiagnostics(*llvm::vfs::getRealFileSystem(), DiagOpts,
+                                 DiagPrinter.get(), /*ShouldOwnClient=*/false);
 
   Diags->Report(diag::err_expected) << "no crash";
   ASSERT_EQ(DiagnosticOutput, "error: expected no crash\n");
diff --git a/clang/unittests/Frontend/CompilerInvocationTest.cpp b/clang/unittests/Frontend/CompilerInvocationTest.cpp
index 45478de..4ff6824 100644
--- a/clang/unittests/Frontend/CompilerInvocationTest.cpp
+++ b/clang/unittests/Frontend/CompilerInvocationTest.cpp
@@ -12,6 +12,7 @@
 #include "clang/Frontend/TextDiagnosticBuffer.h"
 #include "clang/Lex/PreprocessorOptions.h"
 #include "clang/Serialization/ModuleFileExtension.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/TargetParser/Host.h"
 
 #include "gmock/gmock.h"
@@ -38,9 +39,9 @@ public:
   }
 
   CommandLineTest()
-      : Diags(CompilerInstance::createDiagnostics(new DiagnosticOptions(),
-                                                  new TextDiagnosticBuffer())) {
-  }
+      : Diags(CompilerInstance::createDiagnostics(
+            *llvm::vfs::getRealFileSystem(), new DiagnosticOptions(),
+            new TextDiagnosticBuffer())) {}
 };
 
 template <typename M>
diff --git a/clang/unittests/Frontend/FrontendActionTest.cpp b/clang/unittests/Frontend/FrontendActionTest.cpp
index 6ce9ba6..75e1667 100644
--- a/clang/unittests/Frontend/FrontendActionTest.cpp
+++ b/clang/unittests/Frontend/FrontendActionTest.cpp
@@ -20,6 +20,7 @@
 #include "clang/Serialization/InMemoryModuleCache.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/ToolOutputFile.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/TargetParser/Triple.h"
 #include "gtest/gtest.h"
 
@@ -90,7 +91,7 @@ TEST(ASTFrontendAction, Sanity) {
   invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance compiler;
   compiler.setInvocation(std::move(invocation));
-  compiler.createDiagnostics();
+  compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   TestASTFrontendAction test_action;
   ASSERT_TRUE(compiler.ExecuteAction(test_action));
@@ -110,7 +111,7 @@ TEST(ASTFrontendAction, IncrementalParsing) {
   invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance compiler;
   compiler.setInvocation(std::move(invocation));
-  compiler.createDiagnostics();
+  compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   TestASTFrontendAction test_action(/*enableIncrementalProcessing=*/true);
   ASSERT_TRUE(compiler.ExecuteAction(test_action));
@@ -137,7 +138,7 @@ TEST(ASTFrontendAction, LateTemplateIncrementalParsing) {
   invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance compiler;
   compiler.setInvocation(std::move(invocation));
-  compiler.createDiagnostics();
+  compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   TestASTFrontendAction test_action(/*enableIncrementalProcessing=*/true,
                                     /*actOnEndOfTranslationUnit=*/true);
@@ -183,7 +184,7 @@ TEST(PreprocessorFrontendAction, EndSourceFile) {
   Invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance Compiler;
   Compiler.setInvocation(std::move(Invocation));
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   TestPPCallbacks *Callbacks = new TestPPCallbacks;
   TestPPCallbacksFrontendAction TestAction(Callbacks);
@@ -245,7 +246,8 @@ TEST(ASTFrontendAction, ExternalSemaSource) {
   CompilerInstance Compiler;
   Compiler.setInvocation(std::move(Invocation));
   auto *TDC = new TypoDiagnosticConsumer;
-  Compiler.createDiagnostics(TDC, /*ShouldOwnClient=*/true);
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem(), TDC,
+                             /*ShouldOwnClient=*/true);
   Compiler.setExternalSemaSource(new TypoExternalSemaSource(Compiler));
 
   SyntaxOnlyAction TestAction;
@@ -277,7 +279,7 @@ TEST(GeneratePCHFrontendAction, CacheGeneratedPCH) {
     Invocation->getTargetOpts().Triple = "x86_64-apple-darwin19.0.0";
     CompilerInstance Compiler;
     Compiler.setInvocation(std::move(Invocation));
-    Compiler.createDiagnostics();
+    Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
     GeneratePCHAction TestAction;
     ASSERT_TRUE(Compiler.ExecuteAction(TestAction));
diff --git a/clang/unittests/Frontend/OutputStreamTest.cpp b/clang/unittests/Frontend/OutputStreamTest.cpp
index 2618558..fa5d726 100644
--- a/clang/unittests/Frontend/OutputStreamTest.cpp
+++ b/clang/unittests/Frontend/OutputStreamTest.cpp
@@ -13,6 +13,7 @@
 #include "clang/Frontend/TextDiagnosticPrinter.h"
 #include "clang/FrontendTool/Utils.h"
 #include "clang/Lex/PreprocessorOptions.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -37,7 +38,7 @@ TEST(FrontendOutputTests, TestOutputStream) {
 
   Compiler.setOutputStream(std::move(IRStream));
   Compiler.setInvocation(std::move(Invocation));
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   bool Success = ExecuteCompilerInvocation(&Compiler);
   EXPECT_TRUE(Success);
@@ -62,6 +63,7 @@ TEST(FrontendOutputTests, TestVerboseOutputStreamShared) {
   Compiler.setInvocation(std::move(Invocation));
   IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
   Compiler.createDiagnostics(
+      *llvm::vfs::getRealFileSystem(),
       new TextDiagnosticPrinter(llvm::nulls(), &*DiagOpts), true);
   Compiler.setVerboseOutputStream(VerboseStream);
 
@@ -91,6 +93,7 @@ TEST(FrontendOutputTests, TestVerboseOutputStreamOwned) {
     Compiler.setInvocation(std::move(Invocation));
     IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
     Compiler.createDiagnostics(
+        *llvm::vfs::getRealFileSystem(),
         new TextDiagnosticPrinter(llvm::nulls(), &*DiagOpts), true);
     Compiler.setVerboseOutputStream(std::move(VerboseStream));
 
diff --git a/clang/unittests/Frontend/PCHPreambleTest.cpp b/clang/unittests/Frontend/PCHPreambleTest.cpp
index 2ce24c9..58ec2e2 100644
--- a/clang/unittests/Frontend/PCHPreambleTest.cpp
+++ b/clang/unittests/Frontend/PCHPreambleTest.cpp
@@ -94,8 +94,9 @@ public:
     PreprocessorOptions &PPOpts = CI->getPreprocessorOpts();
     PPOpts.RemappedFilesKeepOriginalName = true;
 
-    IntrusiveRefCntPtr<DiagnosticsEngine>
-      Diags(CompilerInstance::createDiagnostics(new DiagnosticOptions, new DiagnosticConsumer));
+    IntrusiveRefCntPtr<DiagnosticsEngine> Diags(
+        CompilerInstance::createDiagnostics(*VFS, new DiagnosticOptions,
+                                            new DiagnosticConsumer));
 
     FileManager *FileMgr = new FileManager(FSOpts, VFS);
 
diff --git a/clang/unittests/Frontend/ReparseWorkingDirTest.cpp b/clang/unittests/Frontend/ReparseWorkingDirTest.cpp
index ca7ce23..b0f2d51 100644
--- a/clang/unittests/Frontend/ReparseWorkingDirTest.cpp
+++ b/clang/unittests/Frontend/ReparseWorkingDirTest.cpp
@@ -58,7 +58,7 @@ public:
     CI->getTargetOpts().Triple = "i386-unknown-linux-gnu";
 
     IntrusiveRefCntPtr<DiagnosticsEngine> Diags(
-        CompilerInstance::createDiagnostics(new DiagnosticOptions,
+        CompilerInstance::createDiagnostics(*VFS, new DiagnosticOptions,
                                             new DiagnosticConsumer));
 
     FileManager *FileMgr = new FileManager(CI->getFileSystemOpts(), VFS);
diff --git a/clang/unittests/Frontend/UtilsTest.cpp b/clang/unittests/Frontend/UtilsTest.cpp
index ae014d3..304fbe2 100644
--- a/clang/unittests/Frontend/UtilsTest.cpp
+++ b/clang/unittests/Frontend/UtilsTest.cpp
@@ -28,9 +28,9 @@ TEST(BuildCompilerInvocationTest, RecoverMultipleJobs) {
   clang::IgnoringDiagConsumer D;
   CreateInvocationOptions Opts;
   Opts.RecoverOnError = true;
-  Opts.Diags = clang::CompilerInstance::createDiagnostics(new DiagnosticOptions,
-                                                          &D, false);
   Opts.VFS = new llvm::vfs::InMemoryFileSystem();
+  Opts.Diags = clang::CompilerInstance::createDiagnostics(
+      *Opts.VFS, new DiagnosticOptions, &D, false);
   std::unique_ptr<CompilerInvocation> CI = createInvocation(Args, Opts);
   ASSERT_TRUE(CI);
   EXPECT_THAT(CI->TargetOpts->Triple, testing::StartsWith("i386-"));
@@ -46,7 +46,7 @@ TEST(BuildCompilerInvocationTest, ProbePrecompiled) {
 
   clang::IgnoringDiagConsumer D;
   llvm::IntrusiveRefCntPtr<DiagnosticsEngine> CommandLineDiagsEngine =
-      clang::CompilerInstance::createDiagnostics(new DiagnosticOptions, &D,
+      clang::CompilerInstance::createDiagnostics(*FS, new DiagnosticOptions, &D,
                                                  false);
   // Default: ProbePrecompiled=false
   CreateInvocationOptions CIOpts;
diff --git a/clang/unittests/Sema/SemaNoloadLookupTest.cpp b/clang/unittests/Sema/SemaNoloadLookupTest.cpp
index cf89c73..a8e1bb0 100644
--- a/clang/unittests/Sema/SemaNoloadLookupTest.cpp
+++ b/clang/unittests/Sema/SemaNoloadLookupTest.cpp
@@ -57,11 +57,12 @@ public:
     std::string FileName = llvm::Twine(ModuleName + ".cppm").str();
     addFile(FileName, Contents);
 
-    IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-        CompilerInstance::createDiagnostics(new DiagnosticOptions());
     CreateInvocationOptions CIOpts;
+    CIOpts.VFS = llvm::vfs::getRealFileSystem();
+    IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+        CompilerInstance::createDiagnostics(*CIOpts.VFS,
+                                            new DiagnosticOptions());
     CIOpts.Diags = Diags;
-    CIOpts.VFS = llvm::vfs::createPhysicalFileSystem();
 
     std::string CacheBMIPath =
         llvm::Twine(TestDir + "/" + ModuleName + ".pcm").str();
diff --git a/clang/unittests/Serialization/ForceCheckFileInputTest.cpp b/clang/unittests/Serialization/ForceCheckFileInputTest.cpp
index ad8892b..6a839d1 100644
--- a/clang/unittests/Serialization/ForceCheckFileInputTest.cpp
+++ b/clang/unittests/Serialization/ForceCheckFileInputTest.cpp
@@ -63,12 +63,14 @@ export int aa = 43;
   std::string BMIPath = llvm::Twine(TestDir + "/a.pcm").str();
 
   {
-    IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-        CompilerInstance::createDiagnostics(new DiagnosticOptions());
     CreateInvocationOptions CIOpts;
-    CIOpts.Diags = Diags;
     CIOpts.VFS = llvm::vfs::createPhysicalFileSystem();
 
+    IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+        CompilerInstance::createDiagnostics(*CIOpts.VFS,
+                                            new DiagnosticOptions());
+    CIOpts.Diags = Diags;
+
     const char *Args[] = {"clang++",       "-std=c++20",
                           "--precompile",  "-working-directory",
                           TestDir.c_str(), "a.cppm"};
@@ -103,11 +105,12 @@ export int aa = 43;
   }
 
   {
-    IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-        CompilerInstance::createDiagnostics(new DiagnosticOptions());
     CreateInvocationOptions CIOpts;
-    CIOpts.Diags = Diags;
     CIOpts.VFS = llvm::vfs::createPhysicalFileSystem();
+    IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+        CompilerInstance::createDiagnostics(*CIOpts.VFS,
+                                            new DiagnosticOptions());
+    CIOpts.Diags = Diags;
 
     std::string BMIPath = llvm::Twine(TestDir + "/a.pcm").str();
     const char *Args[] = {
diff --git a/clang/unittests/Serialization/ModuleCacheTest.cpp b/clang/unittests/Serialization/ModuleCacheTest.cpp
index a7ca985..6ceee1c 100644
--- a/clang/unittests/Serialization/ModuleCacheTest.cpp
+++ b/clang/unittests/Serialization/ModuleCacheTest.cpp
@@ -106,11 +106,11 @@ TEST_F(ModuleCacheTest, CachedModuleNewPath) {
 
   SmallString<256> MCPArg("-fmodules-cache-path=");
   MCPArg.append(ModuleCachePath);
-  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-      CompilerInstance::createDiagnostics(new DiagnosticOptions());
   CreateInvocationOptions CIOpts;
-  CIOpts.Diags = Diags;
   CIOpts.VFS = llvm::vfs::createPhysicalFileSystem();
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+      CompilerInstance::createDiagnostics(*CIOpts.VFS, new DiagnosticOptions());
+  CIOpts.Diags = Diags;
 
   // First run should pass with no errors
   const char *Args[] = {"clang",        "-fmodules",          "-Fframeworks",
@@ -156,11 +156,11 @@ TEST_F(ModuleCacheTest, CachedModuleNewPathAllowErrors) {
 
   SmallString<256> MCPArg("-fmodules-cache-path=");
   MCPArg.append(ModuleCachePath);
-  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-      CompilerInstance::createDiagnostics(new DiagnosticOptions());
   CreateInvocationOptions CIOpts;
-  CIOpts.Diags = Diags;
   CIOpts.VFS = llvm::vfs::createPhysicalFileSystem();
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+      CompilerInstance::createDiagnostics(*CIOpts.VFS, new DiagnosticOptions());
+  CIOpts.Diags = Diags;
 
   // First run should pass with no errors
   const char *Args[] = {"clang",        "-fmodules",          "-Fframeworks",
diff --git a/clang/unittests/Serialization/NoCommentsTest.cpp b/clang/unittests/Serialization/NoCommentsTest.cpp
index a0a564a..a1fb234 100644
--- a/clang/unittests/Serialization/NoCommentsTest.cpp
+++ b/clang/unittests/Serialization/NoCommentsTest.cpp
@@ -83,11 +83,11 @@ export module Comments;
 void foo() {}
   )cpp");
 
-  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-      CompilerInstance::createDiagnostics(new DiagnosticOptions());
   CreateInvocationOptions CIOpts;
-  CIOpts.Diags = Diags;
   CIOpts.VFS = llvm::vfs::createPhysicalFileSystem();
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+      CompilerInstance::createDiagnostics(*CIOpts.VFS, new DiagnosticOptions());
+  CIOpts.Diags = Diags;
 
   std::string CacheBMIPath = llvm::Twine(TestDir + "/Comments.pcm").str();
   const char *Args[] = {"clang++",       "-std=c++20",
diff --git a/clang/unittests/Serialization/PreambleInNamedModulesTest.cpp b/clang/unittests/Serialization/PreambleInNamedModulesTest.cpp
index d26e1cb..cf317ed 100644
--- a/clang/unittests/Serialization/PreambleInNamedModulesTest.cpp
+++ b/clang/unittests/Serialization/PreambleInNamedModulesTest.cpp
@@ -75,10 +75,10 @@ export using ::E;
   )cpp",
           MainFilePath);
 
-  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-      CompilerInstance::createDiagnostics(new DiagnosticOptions());
   IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS =
       llvm::vfs::createPhysicalFileSystem();
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+      CompilerInstance::createDiagnostics(*VFS, new DiagnosticOptions());
 
   CreateInvocationOptions CIOpts;
   CIOpts.Diags = Diags;
diff --git a/clang/unittests/Serialization/VarDeclConstantInitTest.cpp b/clang/unittests/Serialization/VarDeclConstantInitTest.cpp
index 5cbbfb9..14c0c30 100644
--- a/clang/unittests/Serialization/VarDeclConstantInitTest.cpp
+++ b/clang/unittests/Serialization/VarDeclConstantInitTest.cpp
@@ -90,11 +90,11 @@ export namespace Fibonacci
 }
   )cpp");
 
-  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-      CompilerInstance::createDiagnostics(new DiagnosticOptions());
   CreateInvocationOptions CIOpts;
-  CIOpts.Diags = Diags;
   CIOpts.VFS = llvm::vfs::createPhysicalFileSystem();
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+      CompilerInstance::createDiagnostics(*CIOpts.VFS, new DiagnosticOptions());
+  CIOpts.Diags = Diags;
 
   const char *Args[] = {"clang++",       "-std=c++20",
                         "--precompile",  "-working-directory",
diff --git a/clang/unittests/Support/TimeProfilerTest.cpp b/clang/unittests/Support/TimeProfilerTest.cpp
index 339b470..995ebf6 100644
--- a/clang/unittests/Support/TimeProfilerTest.cpp
+++ b/clang/unittests/Support/TimeProfilerTest.cpp
@@ -45,8 +45,6 @@ std::string teardownProfiler() {
 // We only parse AST here. This is enough for constexpr evaluation.
 bool compileFromString(StringRef Code, StringRef Standard, StringRef File,
                        llvm::StringMap<std::string> Headers = {}) {
-  CompilerInstance Compiler;
-  Compiler.createDiagnostics();
 
   llvm::IntrusiveRefCntPtr<llvm::vfs::InMemoryFileSystem> FS(
       new llvm::vfs::InMemoryFileSystem());
@@ -57,6 +55,8 @@ bool compileFromString(StringRef Code, StringRef Standard, StringRef File,
   }
   llvm::IntrusiveRefCntPtr<FileManager> Files(
       new FileManager(FileSystemOptions(), FS));
+  CompilerInstance Compiler;
+  Compiler.createDiagnostics(Files->getVirtualFileSystem());
   Compiler.setFileManager(Files.get());
 
   auto Invocation = std::make_shared<CompilerInvocation>();
diff --git a/clang/unittests/Tooling/DependencyScanning/DependencyScannerTest.cpp b/clang/unittests/Tooling/DependencyScanning/DependencyScannerTest.cpp
index ec0e143..e1c4770 100644
--- a/clang/unittests/Tooling/DependencyScanning/DependencyScannerTest.cpp
+++ b/clang/unittests/Tooling/DependencyScanning/DependencyScannerTest.cpp
@@ -60,7 +60,8 @@ public:
     Compiler.setInvocation(std::move(Invocation));
     Compiler.setFileManager(FileMgr);
 
-    Compiler.createDiagnostics(DiagConsumer, /*ShouldOwnClient=*/false);
+    Compiler.createDiagnostics(FileMgr->getVirtualFileSystem(), DiagConsumer,
+                               /*ShouldOwnClient=*/false);
     if (!Compiler.hasDiagnostics())
       return false;
 
diff --git a/clang/unittests/Tooling/ToolingTest.cpp b/clang/unittests/Tooling/ToolingTest.cpp
index f41a44fa..0b65577 100644
--- a/clang/unittests/Tooling/ToolingTest.cpp
+++ b/clang/unittests/Tooling/ToolingTest.cpp
@@ -384,7 +384,8 @@ struct CommandLineExtractorTest : public ::testing::Test {
 public:
   CommandLineExtractorTest()
       : InMemoryFS(new llvm::vfs::InMemoryFileSystem),
-        Diags(CompilerInstance::createDiagnostics(new DiagnosticOptions)),
+        Diags(CompilerInstance::createDiagnostics(*InMemoryFS,
+                                                  new DiagnosticOptions)),
         Driver("clang", llvm::sys::getDefaultTargetTriple(), *Diags,
                "clang LLVM compiler", overlayRealFS(InMemoryFS)) {}