Support failable Initializers for Opaque Types

[NiwakaDev]

Something like:

#[swift_bridge::bridge]
mod ffi {
    extern "Rust" {
        type SomeType;
        #[swift_bridge(init)]
        fn new() -> Result<SomeType, String>;
    }
}

do {
   let someType = try SomeType()
} catch let error {
   //..
}

Or

#[swift_bridge::bridge]
mod ffi {
    extern "Rust" {
        type SomeType;
        #[swift_bridge(init)]
        fn new() -> Option<SomeType>;
    }
}

if let someType = SomeType() {
    //...
}

I'd like to use this feature, but I don't know whether or not other users would like to.

[chinedufn]

I hadn't heard of this feature. Yeah this sounds like something that we want to support.

https://docs.swift.org/swift-book/documentation/the-swift-programming-language/initialization/#Failable-Initializers

I'm thinking we should also add a #[swift_bridge(init)] section to the Function Attributes documentation and have that section's bridge module show both regular and failable initializers

swift-bridge/book/src/bridge-module/functions/README.md

Line 66 in 2724644

## Function Attributes

[nafehshoaib]

Any updates on this? Would love to use failable initializers instead of a static methods that return optionals

[NiwakaDev]

@nafehshoaib

Any updates on this?

Not yet.

Would love to use failable initializers instead of a static methods that return optionals

I guess that I can implement this issue in three weeks if needed.

[NiwakaDev]

@chinedufn
Can I implement this feature?

[chinedufn]

Yeah that would be great.

I think "Failable Initializers" are ones that return an Option.
We can refer to inits that can throw as "Throwing Initializers".

Feel free to implement either or both.