Use default arguments instead of overloads.

[asoffer]

Use default arguments instead of overloads.

[asoffer]

Remove non-existant overload from cpp file.

clang/include/clang/Frontend/ASTUnit.h

public:
   /// \param Filename - The AST file to load.
   ///
   /// \param PCHContainerRdr - The PCHContainerOperations to use for loading and
   /// creating modules.
   /// \param Diags - The diagnostics engine to use for reporting errors; its
   /// lifetime is expected to extend past that of the returned ASTUnit.
   ///
   /// \returns - The initialized ASTUnit or null if the AST failed to load.
-  static std::unique_ptr<ASTUnit>
-  LoadFromASTFile(const std::string &Filename,
-                  const PCHContainerReader &PCHContainerRdr, WhatToLoad ToLoad,
-                  IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
-                  const FileSystemOptions &FileSystemOpts,
-                  bool UseDebugInfo = false, bool OnlyLocalDecls = false,
-                  CaptureDiagsKind CaptureDiagnostics = CaptureDiagsKind::None,
-                  bool AllowASTWithCompilerErrors = false,
-                  bool UserFilesAreVolatile = false);
+  static std::unique_ptr<ASTUnit> LoadFromASTFile(
+      const std::string &Filename, const PCHContainerReader &PCHContainerRdr,
+      WhatToLoad ToLoad, IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+      IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
+      const FileSystemOptions &FileSystemOpts, bool UseDebugInfo = false,
+      bool OnlyLocalDecls = false,
+      CaptureDiagsKind CaptureDiagnostics = CaptureDiagsKind::None,
+      bool AllowASTWithCompilerErrors = false,
+      bool UserFilesAreVolatile = false);
+  static std::unique_ptr<ASTUnit> LoadFromASTFile(
+      const std::string &Filename, const PCHContainerReader &PCHContainerRdr,
+      WhatToLoad ToLoad, IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+      const FileSystemOptions &FileSystemOpts, bool UseDebugInfo = false,
+      bool OnlyLocalDecls = false,
 
  private:
   /// Helper function for \c LoadFromCompilerInvocation() and
   /// \c LoadFromCommandLine(), which loads an AST from a compiler invocation.
   ///
   /// \param PrecompilePreambleAfterNParses After how many parses the preamble
   /// of this translation unit should be precompiled, to improve the performance
   /// of reparsing. Set to zero to disable preambles.
   ///
   /// \param VFS - A llvm::vfs::FileSystem to be used for all file accesses.

clang/lib/Frontend/ASTUnit.cpp

if (CaptureDiagnostics != CaptureDiagsKind::None)
     Diags->setClient(new FilterAndStoreDiagnosticConsumer(
         &AST.StoredDiagnostics, nullptr,
         CaptureDiagnostics != CaptureDiagsKind::AllWithoutNonErrorsFromIncludes));
 }
 
 std::unique_ptr<ASTUnit> ASTUnit::LoadFromASTFile(
     const std::string &Filename, const PCHContainerReader &PCHContainerRdr,
     WhatToLoad ToLoad, IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+    IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
     const FileSystemOptions &FileSystemOpts, bool UseDebugInfo,
     bool OnlyLocalDecls, CaptureDiagsKind CaptureDiagnostics,
     bool AllowASTWithCompilerErrors, bool UserFilesAreVolatile) {
   std::unique_ptr<ASTUnit> AST(new ASTUnit(true));
 
   // Recover resources if we crash before exiting this method.
   llvm::CrashRecoveryContextCleanupRegistrar<ASTUnit>
     ASTUnitCleanup(AST.get());
   llvm::CrashRecoveryContextCleanupRegistrar<DiagnosticsEngine,
     llvm::CrashRecoveryContextReleaseRefCleanup<DiagnosticsEngine>>
     DiagCleanup(Diags.get());
 
   ConfigureDiags(Diags, *AST, CaptureDiagnostics);
 
   AST->LangOpts = std::make_shared<LangOptions>();
   AST->OnlyLocalDecls = OnlyLocalDecls;
   AST->CaptureDiagnostics = CaptureDiagnostics;
   AST->Diagnostics = Diags;
-  IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS =
-      llvm::vfs::getRealFileSystem();
   AST->FileMgr = new FileManager(FileSystemOpts, VFS);
   AST->UserFilesAreVolatile = UserFilesAreVolatile;
   AST->SourceMgr = new SourceManager(AST->getDiagnostics(),
                                      AST->getFileManager(),
                                      UserFilesAreVolatile);
   AST->ModuleCache = new InMemoryModuleCache;
   AST->HSOpts = std::make_shared<HeaderSearchOptions>();
   AST->HSOpts->ModuleFormat = std::string(PCHContainerRdr.getFormat());
std::unique_ptr<ASTUnit> ASTUnit::LoadFromASTFile(
   }
 
   // Tell the diagnostic client that we have started a source file.
   AST->getDiagnostics().getClient()->BeginSourceFile(PP.getLangOpts(), &PP);
 
   return AST;
 }
 
+std::unique_ptr<ASTUnit> ASTUnit::LoadFromASTFile(
+    const std::string &Filename, const PCHContainerReader &PCHContainerRdr,
+    WhatToLoad ToLoad, IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+    const FileSystemOptions &FileSystemOpts, bool UseDebugInfo,
+    bool OnlyLocalDecls, CaptureDiagsKind CaptureDiagnostics,
+    bool AllowASTWithCompilerErrors, bool UserFilesAreVolatile) {
+  return LoadFromASTFile(Filename, PCHContainerRdr, ToLoad, Diags,
+                         llvm::vfs::getRealFileSystem(), FileSystemOpts,
+                         UseDebugInfo, OnlyLocalDecls, CaptureDiagnostics,
+                         AllowASTWithCompilerErrors, UserFilesAreVolatile);
+}
+
 /// Add the given macro to the hash of all top-level entities.
 static void AddDefinedMacroToHash(const Token &MacroNameTok, unsigned &Hash) {
   Hash = llvm::djbHash(MacroNameTok.getIdentifierInfo()->getName(), Hash);
 }
 
 namespace {
 
 /// Preprocessor callback class that updates a hash value with the names