Method FileError

ext/include/llvm/Support/Error.h:1245–1253

private:
  FileError(const Twine &F, Optional<size_t> LineNum,
            std::unique_ptr<ErrorInfoBase> E) {
    assert(E && "Cannot create FileError from Error success value.");
    assert(!F.isTriviallyEmpty() &&
           "The file name provided to FileError must not be empty.");
    FileName = F.str();
    Err = std::move(E);
    Line = std::move(LineNum);
  }

  static Error build(const Twine &F, Optional<size_t> Line, Error E) {
    std::unique_ptr<ErrorInfoBase> Payload;