Jeremy Fitzhardinge 4f7f38c1a0 rust/failure_ext: add .chain()/Chain ... Summary: Add a type to explicitly model a causal chain of errors, akin to error_chain. This looks a lot like Context, but is intended to show the entire stack of errors rather than deciding that only the top-level one is interesting. This adds a `ChainExt` trait, which adds a `.chain_ext(OuterError)` method to add another step to the causal chain. This is implemented for: - `F` where `F: Fail` - `Error` - `Result<_, F>` where `F: Fail` - `Result<_, Error>` - `Future`/`Stream<Error=F>` where `F: Fail` - `Future`/`Stream<Error=Error>` - `Chain` Using it is simple: ``` let res = something_faily().chain_err(LocalError::new("Something amiss"))?; ``` where `something_faily()` returns any of the above types. (This is done by adding an extra dummy marker type parameter to the `ChainExt` trait so that it can avoid problems with the coherence rules - thanks for the idea @[100000771202578:kulshrax]!) Reviewed By: lukaspiatkowski Differential Revision: D9394192 fbshipit-source-id: 0817844d283b3900d2555f526c2683231ca7fe12		2018-09-06 14:24:08 -07:00
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src	rust/failure_ext: add .chain()/Chain	2018-09-06 14:24:08 -07:00
Cargo.toml	rust/failure_ext: add .chain()/Chain	2018-09-06 14:24:08 -07:00