Missing Error impl for throw MyError fn

[boozook]

The type returned by a function as second part of the Result must implement the Error protocol. For example:

struct MyErr;
fn err() -> Result<(), MyErr> { Ok(()) }
fn string() -> Result<(), String> { Ok(()) }

#[swift_bridge::bridge]
mod ffi {
	extern "Rust" {
		type MyErr;

		fn err() -> Result<(), MyErr>;
		fn string() -> Result<(), String>;
	}
}

Error: Thrown expression type 'RustString' does not conform to 'Error'
Produced Swift:

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Workaround is to add impl by hand:

extension MyErr: Error {}
extension RustString: Error {}

But this is not refactorible and could be great to have one of following options:

• generate extension {Ty}: Error {} automatically
• generate extension {Ty}: Error {} by rust attribute like #[swift_bridge(impl(Error))] type MyErr;
• inject user's raw swift-source into generated output.

First and second are the best, imho.

[chinedufn]

Thanks for opening this issue.

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Support for -> Resutlt<*, String> is implemented and will be available in the next release #296

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Support for the Error protocol is tracked in #150 , so I'll close this in favor of that issue.
If you or any future person that sees this is interested in implementing support for the Error protocol I'd be happy to provide hand-held guidance and answer all questions.

[boozook]

@chinedufn Thanks! Impl for String is good but I need to know is that error recoverable or not, so I need a custom struct/enum.

[chinedufn]

Anytime.

#150 would solve your problem., or are you suggesting otherwise?

[boozook]

Partially. Could be great to have something like #[swift_bridge(Sendable, Error)] type Foo;.

[boozook]

#150 would solve your problem., or are you suggesting otherwise?

Looks like good enough, as I hope. Thanks! 😊