[clang] Change FileManager to use llvm::ErrorOr instead of null on fa…

…ilure

Summary:
Currently, clang's FileManager uses NULL as an indicator that a particular file
did not exist, but would not propagate errors like permission issues. Instead,
teach FileManager to use llvm::ErrorOr internally and return rich errors for
failures.

Reviewers: arphaman, bruno, martong, shafik

Subscribers: nemanjai, kbarton, MaskRay, jkorous, dexonsmith, kadircet, jsji, cfe-commits, lldb-commits

Tags: #clang, #lldb

Differential Revision: https://reviews.llvm.org/D65534

llvm-svn: 367618

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

@@ -908,10 +908,13 @@ ClangExpressionParser::ParseInternal(DiagnosticManager &diagnostic_manager,
       if (file.Write(expr_text, bytes_written).Success()) {
         if (bytes_written == expr_text_len) {
           file.Close();
-          source_mgr.setMainFileID(source_mgr.createFileID(
-              m_compiler->getFileManager().getFile(result_path),
-              SourceLocation(), SrcMgr::C_User));
-          created_main_file = true;
+          if (auto fileEntry =
+                  m_compiler->getFileManager().getFile(result_path)) {
+            source_mgr.setMainFileID(source_mgr.createFileID(
+                *fileEntry,
+                SourceLocation(), SrcMgr::C_User));
+            created_main_file = true;
+          }
         }
       }
     }

lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp

@@ -247,11 +247,11 @@ bool ClangModulesDeclVendorImpl::AddModule(const SourceModule &module,
 
       bool is_system = true;
       bool is_framework = false;
-      auto *dir =
+      auto dir =
           HS.getFileMgr().getDirectory(module.search_path.GetStringRef());
       if (!dir)
         return error();
-      auto *file = HS.lookupModuleMapFile(dir, is_framework);
+      auto *file = HS.lookupModuleMapFile(*dir, is_framework);
       if (!file)
         return error();
       if (!HS.loadModuleMapFile(file, is_system))