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, 1 insertions, 3 deletions

diff --git a/clang/lib/Lex/HeaderMap.cpp b/clang/lib/Lex/HeaderMap.cpp
index 1c7fb1a..d44ef29c 100644
--- a/clang/lib/Lex/HeaderMap.cpp
+++ b/clang/lib/Lex/HeaderMap.cpp
@@ -204,9 +204,7 @@ Optional<FileEntryRef> HeaderMap::LookupFile(StringRef Filename,
   if (Dest.empty())
     return None;
 
-  if (auto File = FM.getFileRef(Dest))
-    return *File;
-  return None;
+  return FM.getOptionalFileRef(Dest);
 }
 
 StringRef HeaderMapImpl::lookupFilename(StringRef Filename,