Add test cases for Option<&T> and fix rust codegen

[PrismaPhonic]

Add test cases for Option<&T> and fix rust codegen

Currently swift-bridge only has tests for Option - this adds test cases for Option<&T> and fixes a bug in rust codegen that does not correctly translate Option<&T>.

This is now possible:

mod ffi {
  extern "Rust" {
    type MyStruct;

    fn my_func(arg: Option<&MyStruct>) -> Option<&MyStruct>;
  }
}

[PrismaPhonic]

I've addressed all concerns listed here but seem to still hit this compiler error:

error[E0308]: mismatched types
   --> crates/swift-integration-tests/src/option.rs:95:13
    |
3   | #[swift_bridge::bridge]
    | ----------------------- arguments to this function are incorrect
...
95  |             arg: Option<&OptTestOpaqueRustType>,
    |             ^^^ types differ in mutability
    |
    = note: expected raw pointer `*mut _`
               found raw pointer `*const OptTestOpaqueRustType`
note: associated function defined here
   --> /home/pmfarr/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/boxed.rs:950:19
    |
950 |     pub unsafe fn from_raw(raw: *mut T) -> Self {

EDIT: Do you know if there's way to have the compiler show the error at the expanded code? I know I can cargo expand to see the full expansion but I'd love it if I could link cargo check to show the expanded version. These compiler errors aren't the most useful since they always point at the macro.

I think that we are generating a function that takes in a const (which it should) but then tries to call Box::from_raw() on it which wants a mut - but I'm not sure where to fix that

[chinedufn]

Do you know if there's way to have the compiler show the error at the expanded code?

I think there's a rustc flag for it but I've never used it https://stackoverflow.com/a/68843349

I think that we are generating a function that takes in a const (which it should) but then tries to call Box::from_raw() on it which wants a mut - but I'm not sure where to fix that

Yup. Can do another if self.reference in here:

https://github.com/chinedufn/swift-bridge/blob/4fbd30f81085dc366bda3c0303eac66345de3ed9/crates/swift-bridge-ir/src/bridged_type/bridged_opaque_type.rs#L438

Something like:

if self.reference {
    Some(unsafe {& * #expression})
} else {
    Some(unsafe { * Box::from_raw(#expression) } )
}

[PrismaPhonic]

Do you know if there's way to have the compiler show the error at the expanded code?

I think there's a rustc flag for it but I've never used it https://stackoverflow.com/a/68843349

I think that we are generating a function that takes in a const (which it should) but then tries to call Box::from_raw() on it which wants a mut - but I'm not sure where to fix that

Yup. Can do another if self.reference in here:

https://github.com/chinedufn/swift-bridge/blob/4fbd30f81085dc366bda3c0303eac66345de3ed9/crates/swift-bridge-ir/src/bridged_type/bridged_opaque_type.rs#L438

Something like:

if self.reference {
    Some(unsafe {& * #expression})
} else {
    Some(unsafe { * Box::from_raw(#expression) } )
}

Done, annnnnd now I'm hitting way more compiler errors :(

error[E0424]: expected value, found module `self`
  --> crates/swift-integration-tests/src/option.rs:3:1
   |
3  | #[swift_bridge::bridge]
   | ^^^^^^^^^^^^^^^^^^^^^^^ `self` value is a keyword only available in methods with a `self` parameter
...
90 |         fn rust_reflect_option_opaque_rust_type(
   |            ------------------------------------ this function can't have a `self` parameter
   |
   = note: this error originates in the attribute macro `swift_bridge::bridge` (in Nightly builds, run with -Z macro-backtrace for more info)

Somehow now we are generating functions that don't have self to have self. I'm soooooo confused

[chinedufn]

Done, annnnnd now I'm hitting way more compiler errors :(

Ah gotcha. Just need the self to be outside of the quote! :

if self.reference {
    quote! {
        if #expression.is_null() {
            None
        } else {
            Some(unsafe {& * #expression})
        }
    }
} else {
    quote! {
        if #expression.is_null() {
            None
        } else {
            Some(unsafe { * Box::from_raw(#expression) } )
        }
    }
}

[PrismaPhonic]

@chinedufn addressed all issues - all tests are passing for me locally (using the command in the README)

EDIT: I am seeing now that command from the README seems to only run the rust tests. How do I have it run the swift tests?

EDIT-EDIT: Ran them from my Macbook and all working! I do all of my Rust dev on my work laptop (Arch Linux) and so it wasn't running the swift tests. Should be good to go to run in CI now

[PrismaPhonic]

Huh, I wonder why integration tests failed in the pipeline but that one test in particular succeeds locally for me

[chinedufn]

Mind pushing new commits instead of force pushing? This way I can see what has changed. I'll squash them all at the end.

[PrismaPhonic]

Mind pushing new commits instead of force pushing? This way I can see what has changed. I'll squash them all at the end.

Can do - Github in particular has this problem unfortunately. In other platforms you can see a diff between rebases

[PrismaPhonic]

Addressed all comments - tests are passing for me locally now

[chinedufn]

Thanks for reporting this issue and thanks for putting together a fix. Appreciate you pushing through the unexpected compile time error after compile time error after compile time error.

Cheers.