Jeremy Fitzhardinge b44055a6b3 rust/failure_ext: add err_downcast/err_downcast_ref macros ... Summary: Add a pair of macros to make downcasting errors less tedious: ``` let res = err_downcast! { err, // failure::Error foo: FooError => { println!("err is an FooError! {:?}", foo) }, bar: BarError => { println!("err is a BarError! {:?}", bar) }, }; ``` `err_downcast` takes `failure::Error` and deconstructs it into one of the desired types and returns `Ok(match action)`, or returning it as `Err(Error)` if nothing matches. `err_downcast_ref` takes `&failure::Error` and gives a reference type. It returns `Some(match action)` or `None` if nothing matches. The error types are required to implement `failure::Fail`. `err_downcast_ref` also matches each error type `E` as `Context<E>`. Reviewed By: lukaspiatkowski Differential Revision: D9394193 fbshipit-source-id: c56d91362d5bed8ab3e254bc44bb6f8a0eb376a2		2018-09-06 14:24:06 -07:00
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src	rust/failure_ext: add err_downcast/err_downcast_ref macros	2018-09-06 14:24:06 -07:00
Cargo.toml	tp2/rust: rust-crates-io update	2018-08-02 10:06:47 -07:00