FileManager: Use llvm::Expected in new getFileRef API

`FileManager::getFileRef` is a modern API which we expect to convert to
over time.  We should modernize the error handling as well, using
`llvm::Expected` instead of `llvm::ErrorOr`, to help clients that care
about errors to ensure nothing is missed.

However, not all clients care.  I've also added another path for those
that don't:

- `FileEntryRef` is now copy- and move-assignable (using a pointer
  instead of a reference).
- `FileManager::getOptionalFileRef` returns an `llvm::Optional` instead
  of `llvm::Expected`.
- Added an `llvm::expectedToOptional` utility in case this is useful
  elsewhere.

https://reviews.llvm.org/D66705

llvm-svn: 369943

1 files changed, 6 insertions, 5 deletions

diff --git a/clang/lib/Basic/FileManager.cpp b/clang/lib/Basic/FileManager.cpp
index 649e4d2239b..8e186713a92 100644
--- a/clang/lib/Basic/FileManager.cpp
+++ b/clang/lib/Basic/FileManager.cpp
@@ -187,10 +187,10 @@ FileManager::getFile(StringRef Filename, bool openFile, bool CacheFailure) {
   auto Result = getFileRef(Filename, openFile, CacheFailure);
   if (Result)
     return &Result->getFileEntry();
-  return Result.getError();
+  return llvm::errorToErrorCode(Result.takeError());
 }
 
-llvm::ErrorOr<FileEntryRef>
+llvm::Expected<FileEntryRef>
 FileManager::getFileRef(StringRef Filename, bool openFile, bool CacheFailure) {
   ++NumFileLookups;
 
@@ -199,7 +199,8 @@ FileManager::getFileRef(StringRef Filename, bool openFile, bool CacheFailure) {
       SeenFileEntries.insert({Filename, std::errc::no_such_file_or_directory});
   if (!SeenFileInsertResult.second) {
     if (!SeenFileInsertResult.first->second)
-      return SeenFileInsertResult.first->second.getError();
+      return llvm::errorCodeToError(
+          SeenFileInsertResult.first->second.getError());
     // Construct and return and FileEntryRef, unless it's a redirect to another
     // filename.
     SeenFileEntryOrRedirect Value = *SeenFileInsertResult.first->second;
@@ -230,7 +231,7 @@ FileManager::getFileRef(StringRef Filename, bool openFile, bool CacheFailure) {
     else
       SeenFileEntries.erase(Filename);
 
-    return DirInfoOrErr.getError();
+    return llvm::errorCodeToError(DirInfoOrErr.getError());
   }
   const DirectoryEntry *DirInfo = *DirInfoOrErr;
 
@@ -249,7 +250,7 @@ FileManager::getFileRef(StringRef Filename, bool openFile, bool CacheFailure) {
     else
       SeenFileEntries.erase(Filename);
 
-    return statError;
+    return llvm::errorCodeToError(statError);
   }
 
   assert((openFile || !F) && "undesired open file");