/*! ~~~bash $ cargo run -q --example tutorial11 Main Error Report: func1 error calling func2 Error reported by Func2Error: Error reading 'foo.txt' Debug Error: examples/tutorial11.rs:57: func1 error calling func2 Caused by: examples/tutorial11.rs:32: Func2Error(Error reading 'foo.txt') Caused by: Kind(NotFound) ~~~ !*/ use chainerror::prelude::*; use std::error::Error; use std::io; use std::result::Result; fn do_some_io() -> Result<(), Box> { Err(io::Error::from(io::ErrorKind::NotFound))?; Ok(()) } derive_str_cherr!(Func2Error); fn func2() -> Result<(), Box> { let filename = "foo.txt"; do_some_io().map_err(mstrerr!(Func2Error, "Error reading '{}'", filename))?; Ok(()) } enum Func1Error { Func2, IO(String), } impl ::std::fmt::Display for Func1Error { fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result { match self { Func1Error::Func2 => write!(f, "func1 error calling func2"), Func1Error::IO(filename) => write!(f, "Error reading '{}'", filename), } } } impl ::std::fmt::Debug for Func1Error { fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result { write!(f, "{}", self) } } fn func1() -> ChainResult<(), Func1Error> { func2().map_err(|e| cherr!(e, Func1Error::Func2))?; let filename = String::from("bar.txt"); do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?; Ok(()) } fn main() -> Result<(), Box> { if let Err(e) = func1() { match e.kind() { Func1Error::Func2 => eprintln!("Main Error Report: func1 error calling func2"), Func1Error::IO(filename) => { eprintln!("Main Error Report: func1 error reading '{}'", filename) } } if let Some(e) = e.find_chain_cause::() { eprintln!("Error reported by Func2Error: {}", e) } eprintln!("\nDebug Error:\n{:?}", e); } Ok(()) }