[clang] Pass VFS into `ASTUnit::LoadFromASTFile()` (#159166)

This PR makes the `VFS` parameter to `ASTUnit::LoadFromASTFile()`
required and explicit, rather than silently defaulting to the real file
system. This makes it easy to correctly propagate the fully-configured
VFS and load any input files like the rest of the compiler does.

1 files changed, 3 insertions, 2 deletions

diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 8b35af1..cb44568 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -808,12 +808,13 @@ void ASTUnit::ConfigureDiags(IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
 
 std::unique_ptr<ASTUnit> ASTUnit::LoadFromASTFile(
     StringRef Filename, const PCHContainerReader &PCHContainerRdr,
-    WhatToLoad ToLoad, std::shared_ptr<DiagnosticOptions> DiagOpts,
+    WhatToLoad ToLoad, IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
+    std::shared_ptr<DiagnosticOptions> DiagOpts,
     IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
     const FileSystemOptions &FileSystemOpts, const HeaderSearchOptions &HSOpts,
     const LangOptions *LangOpts, bool OnlyLocalDecls,
     CaptureDiagsKind CaptureDiagnostics, bool AllowASTWithCompilerErrors,
-    bool UserFilesAreVolatile, IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS) {
+    bool UserFilesAreVolatile) {
   std::unique_ptr<ASTUnit> AST(new ASTUnit(true));
 
   // Recover resources if we crash before exiting this method.