A payload can contain any details that the producer of that error believes are important. I don't know what you mean by the error handling trace, how does that help with the toy JSON parsing example? I want the payload to indicate the position in the input string where the parser encountered an error.
I want a function like `diffFiles(path_a, path_b)` to have an error set of `error { ReadError }` with more detailed information in the payload (e.g. file path, translated error code). The alternative is: `error { FileAReadErrorNotFound, FileBReadErrorNotFound, FileAReadErrorPermissionDenied, FileBReadErrorPermissionDenied, ...}`
I want a function like `diffFiles(path_a, path_b)` to have an error set of `error { ReadError }` with more detailed information in the payload (e.g. file path, translated error code). The alternative is: `error { FileAReadErrorNotFound, FileBReadErrorNotFound, FileAReadErrorPermissionDenied, FileBReadErrorPermissionDenied, ...}`