cause

[Cause] is a tiny generic implementation of the [std::error::Error] trait.

It takes 1 type parameter(T: Debug) who describes what error type happened.

It is dereference-able as &T.

And if you use macro [cause], it automatically stores some extra information, the filename and line number, only when it was compiled with debug_assertions.

Examples

```rust

[derive(Debug, PartialEq, Eq)]

pub enum ErrorType { InvalidArgumentsError, InternalError, NotFoundError, }

use ErrorType::*; use cause::Cause;

// It creates an instance of Cause<ErrorType> let cause = Cause::new(InternalError); asserteq!(format!("{}", cause), "InternalError".tostring());

// It is dereference-able. assert_eq!(*cause, InternalError);

let httpstatuscode = match *cause { InternalError => 500, InvalidArgumentsError => 400, NotFoundError => 404, }; asserteq!(httpstatus_code, 500);

// with a message: let cause = Cause::new(InvalidArgumentsError).msg("oops!"); asserteq!( format!("{}", cause), "InvalidArgumentsError: oops!".tostring() );

// with source of error (any error type can be set with src()): let cause = Cause::new(InternalError).src(Cause::new(NotFoundError)); asserteq!( format!("{}", cause), "InternalError\n\nCaused by:\n NotFoundError\n".tostring() );

// an example of Cause who have a standard io error. use std::io::{Error, ErrorKind}; let ioerr = Error::new(ErrorKind::Other, "oh no!"); println!("{}", Cause::new(InternalError).src(ioerr).msg("internal error caused by io error"));

// a couple of macro examples use cause::cause;

let cause = cause!(InternalError); println!("{}", cause); // => "InternalError" on release build // => "InternalError: [lib.rs:59]" on debug build

let cause = cause!(NotFoundError, "There is no such contents."); println!("{}", cause); // => "InternalError: There is no such contents." on release build // => "InternalError: There is no such contents. [lib.rs:59]" on debug build

```

License: MIT