Vicente J. Botet Escriba wrote: ...
Wrap E so that the conversion to Exception can be done, e.g. instead of std::result<bool> we could have expected<bool, filesystem::error_code>
filesystem::error_code is a wrapper for error_code that defines the rethrow function throwing filesystem_error.
The problem here is not just that we have to throw filesystem_error; the problem is that the point of throwing filesystem_error instead of system_error is that it contains the path (two paths even, although we only have one in this case), and there's no path in error_code. If all we had was error_code, the right exception to throw is system_error, because that's what it's for. The correct approach here, I think, is not to define fat error codes, but to return an outcome whose error() is the error_code and whose exception() is the appropriate filesystem_error exception, complete with the path(s). Setting however both the error_code and the exception_ptr is not supported by the current outcome design (and neither would it be supported by expected<R, error_code, exception_ptr>.) Or, an alternative that scales better would be to take http://pdimov.com/cpp2/P0640R0.pdf and store error_code and exception_info, so that later one can use throw_with_info( std::system_error( error() ), info ); with the additional information (such as paths) being carried by the exception_info.