Support Option<OpaqueSwiftType>

[Bright-Shard]

This adds support for bridging Option<OpaqueSwiftType> in extern "Rust" functions. This fixes #268, and makes the following now possible:

#[swift_bridge::bridge]
mod ffi {
    extern "Swift" {
        type SomeSwiftType;
    }

    extern "Rust" {
        fn option_arg(arg: Option<SomeSwiftType>);
        fn returns_option() -> Option<SomeSwiftType>;
    }
}

[Bright-Shard]

Autoformatting did something to the spacing in this whole file... I'll leave a comment where I actually made changes

[Bright-Shard]

Actual changes are here

[Bright-Shard]

Moved here from extern_swift_function_opaque_swift_type_return_codegen_tests.rs... the original issue mentioned moving those tests

[Bright-Shard]

I faced the same issue as #270 - tests wouldn't even compile without this, since -D warnings is enabled for them. I also had to make this change to result.rs below. Maybe there's a better solution, this was just what I did to get tests running

[chinedufn]

Please document:

• why we're allowing dead code
• what needs to happen to remove this allow dead code
• link to the issue

Seems like this can be deleted once #270 is closed. So, yeah just mention that.

This will make it easier for us to eventually stop allowing dead code.

---

Please also apply this feedback to result.rs

[chinedufn]

Nice work. Just one small bit of feedback.

[chinedufn]

Please document:

• why we're allowing dead code
• what needs to happen to remove this allow dead code
• link to the issue

Seems like this can be deleted once #270 is closed. So, yeah just mention that.

This will make it easier for us to eventually stop allowing dead code.

---

Please also apply this feedback to result.rs

[chinedufn]

Looks like tests are failing:

error[E0412]: cannot find type `OptTestOpaqueSwiftType` in module `super`
   --> crates/swift-integration-tests/src/option.rs:128:14
    |
128 |         type OptTestOpaqueSwiftType;
    |              ^^^^^^^^^^^^^^^^^^^^^^ help: a struct with a similar name exists: `OptTestOpaqueRustType`
...
202 | pub struct OptTestOpaqueRustType {
    | -------------------------------- similarly named struct `OptTestOpaqueRustType` defined here

For more information about this error, try `rustc --explain E0412`.
error: could not compile `swift-integration-tests` (lib) due to 1 previous error

[Bright-Shard]

That's embarrassing... I'd removed a use ffi::SwiftType statement and used absolute paths instead... but apparently you have to import the ffi types or it won't compile.

I commented on #270 with the output but on nightly some of the ui tests fail to run as well. Everything seems to pass now on stable though.

[chinedufn]

Hmm, not sure what happened.

Paths should work

swift-bridge/crates/swift-integration-tests/src/option.rs

Lines 326 to 330 in 58f4a40

	fn rust_reflect_option_struct_with_no_data(
	arg: Option<ffi::OptionStruct>,
	) -> Option<ffi::OptionStruct> {
	arg
	}

Cool. Looks good. I'll merge once tests pass.

[chinedufn]

Thanks!

[chinedufn]

Published as 0.1.54 https://crates.io/crates/swift-bridge/0.1.54

[chinedufn]

Replaced the pointer::casts with more explicit as *mut SomeType.

Explained here b4ba1a7

[chinedufn]

When I was working on b4ba1a7 I noticed that when returning Swift types from Rust -> Swift we were running the Drop impl on the Rust representation of the Swift type.

swift-bridge/crates/swift-bridge-ir/src/codegen/codegen_tests/opaque_swift_type_codegen_tests.rs

Lines 26 to 33 in 636fa27

	#[repr(C)]
	pub struct MyType(*mut std::ffi::c_void);
	impl Drop for MyType {
	fn drop (&mut self) {
	unsafe { __swift_bridge__MyType__free(self.0) }
	}
	}

It looks like this #272 PR was avoiding that Drop by incrementing the Swift type's retain count twice instead of once.

This means that we were leaking memory.

My apologies for not thinking of this during review.

Fixed #273

[Bright-Shard]

That makes a lot more sense... I'd assumed for some reason it wasn't automatically incrementing the retain count, and thought I was just doing it once.

[chinedufn]

Got it.

---

0.1.55 has been released https://crates.io/crates/swift-bridge/0.1.55