Small refactoring of FileError. NFC

[evgeny777]

Summary

This was originally suggested in D57738

[jhenderson]

LGTM, with the comment fix.

include/llvm/Support/Error.h

1218–1219

I'd rephrase this slightly to say "Concatenate a source file path and/or name with a std::error_code to form an Error object", and then delete the second sentence.

[rupprecht]

include/llvm/Support/Error.h

1221

errorCodeToError(EC) seems more appropriate, given there is no string

1224

Update this too

include/llvm/Support/Error.h

 Error createStringError(std::error_code EC, char const *Msg);
 
 /// This class wraps a filename and another Error.
 ///
 /// In some cases, an error needs to live along a 'source' name, in order to
 /// show more detailed information to the user.
 class FileError final : public ErrorInfo<FileError> {
 
-  friend Error createFileError(std::string, Error);
+  friend Error createFileError(const Twine &, Error);
 
 public:
   void log(raw_ostream &OS) const override {
     assert(Err && !FileName.empty() && "Trying to log after takeError().");
     OS << "'" << FileName << "': ";
     Err->log(OS);
   }
 
   Error takeError() { return Error(std::move(Err)); }
 
   std::error_code convertToErrorCode() const override;
 
   // Used by ErrorInfo::classID.
   static char ID;
 
 private:
-  FileError(std::string F, std::unique_ptr<ErrorInfoBase> E) {
+  FileError(const Twine &F, std::unique_ptr<ErrorInfoBase> E) {
     assert(E && "Cannot create FileError from Error success value.");
     assert(!F.empty() &&
            "The file name provided to FileError must not be empty.");
-    FileName = F;
+    FileName = F.str();
     Err = std::move(E);
   }
 
-  static Error build(std::string F, Error E) {
+  static Error build(const Twine &F, Error E) {
     return Error(std::unique_ptr<FileError>(new FileError(F, E.takePayload())));
   }
 
   std::string FileName;
   std::unique_ptr<ErrorInfoBase> Err;
 };
 
 /// Concatenate a source file path and/or name with an Error. The resulting
 /// Error is unchecked.
-inline Error createFileError(std::string F, Error E) {
+inline Error createFileError(const Twine &F, Error E) {
   return FileError::build(F, std::move(E));
 }
 
+/// Concatenate a source file path and/or name with an Error. Also build
+/// Error object from std::error_code.
+inline Error createFileError(const Twine &F, std::error_code EC) {
+  return createFileError(F, make_error<StringError>(EC));
+}
+
 Error createFileError(std::string F, ErrorSuccess) = delete;
 
 /// Helper for check-and-exit error handling.
 ///
 /// For tool use only. NOT FOR USE IN LIBRARY CODE.
 ///
 class ExitOnError {
 public:
   /// Create an error on exit helper.

tools/llvm-objcopy/CopyConfig.cpp

 
 static Error addSymbolsToRenameFromFile(StringMap<StringRef> &SymbolsToRename,
                                         BumpPtrAllocator &Alloc,
                                         StringRef Filename) {
   StringSaver Saver(Alloc);
   SmallVector<StringRef, 16> Lines;
   auto BufOrErr = MemoryBuffer::getFile(Filename);
   if (!BufOrErr)
-    return createError(Filename, BufOrErr.getError());
+    return createFileError(Filename, BufOrErr.getError());
 
   BufOrErr.get()->getBuffer().split(Lines, '\n');
   size_t NumLines = Lines.size();
   for (size_t LineNo = 0; LineNo < NumLines; ++LineNo) {
     StringRef TrimmedLine = Lines[LineNo].split('#').first.trim();
     if (TrimmedLine.empty())
       continue;
 

tools/llvm-objcopy/llvm-objcopy.h

 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/raw_ostream.h"
 #include <string>
 
 namespace llvm {
 namespace objcopy {
 
-Error createError(StringRef File, std::error_code EC);
-
 LLVM_ATTRIBUTE_NORETURN extern void error(Twine Message);
 LLVM_ATTRIBUTE_NORETURN extern void error(Error E);
 LLVM_ATTRIBUTE_NORETURN extern void reportError(StringRef File, Error E);
 LLVM_ATTRIBUTE_NORETURN extern void reportError(StringRef File,
                                                 std::error_code EC);
 
 // This is taken from llvm-readobj.
 // [see here](llvm/tools/llvm-readobj/llvm-readobj.h:38)

tools/llvm-objcopy/llvm-objcopy.cpp

 #include <utility>
 
 namespace llvm {
 namespace objcopy {
 
 // The name this program was invoked as.
 StringRef ToolName;
 
-Error createError(StringRef File, std::error_code EC) {
-  assert(EC);  
-  return createFileError(File, make_error<StringError>(EC));
-}
-
 LLVM_ATTRIBUTE_NORETURN void error(Twine Message) {
   WithColor::error(errs(), ToolName) << Message << ".\n";
   errs().flush();
   exit(1);
 }
 
 LLVM_ATTRIBUTE_NORETURN void error(Error E) {
   assert(E);
   std::string Buf;
   raw_string_ostream OS(Buf);
   logAllUnhandledErrors(std::move(E), OS);
   OS.flush();
   WithColor::error(errs(), ToolName) << Buf;
   exit(1);
 }
 
 LLVM_ATTRIBUTE_NORETURN void reportError(StringRef File, std::error_code EC) {
-  error(createError(File, EC));
+  assert(EC);
+  error(createFileError(File, EC));
 }
 
 LLVM_ATTRIBUTE_NORETURN void reportError(StringRef File, Error E) {
   assert(E);
   std::string Buf;
   raw_string_ostream OS(Buf);
   logAllUnhandledErrors(std::move(E), OS);
   OS.flush();