BridgeJS: Swift Array support

[krodak]

BridgeJS: Swift Array Support

This PR adds the ability to pass Swift arrays to and from JavaScript using the BridgeJS plugin.

Example

Swift:

@JS func processNumbers(_ values: [Int]) -> [Int] {
    return values.map { $0 * 2 }
}

@JS func getGreeting() -> [String] {
    return ["Hello", "World", "from", "Swift"]
}

JavaScript:

const doubled = exports.processNumbers([1, 2, 3, 4, 5]);
console.log(doubled); // [2, 4, 6, 8, 10]

const greeting = exports.getGreeting();
console.log(greeting.join(" ")); // "Hello World from Swift"

Generated TypeScript:

export type Exports = {
    processNumbers(values: number[]): number[];
    getGreeting(): string[];
}

Supported Array Types / Features

Swift Feature	Status
Primitive arrays: [Int], [Double], [Bool], [String]	Supported
Struct arrays: [MyStruct]	Supported
Class arrays: [MyClass]	Supported
Enum arrays (case, raw value, associated value)	Supported
Nested arrays: [[Int]]	Supported
Optional arrays: [Int]?	Supported
Arrays of optionals: [Int?]	Supported
Protocol arrays: [MyProtocol]	Supported
UnsafePointer-family arrays	Supported
Default Values	Supported

How It Works

Arrays use copy semantics when crossing the Swift/JavaScript boundary:

• Array elements are pushed to type-specific stacks and reconstructed as JavaScript arrays
• Each side has its own copy - modifications don't affect the original
• Primitive elements are copied by value; class elements copy their references

Testing

• Comprehensive snapshot tests for array codegen
• Runtime tests covering primitive, struct, class, enum, optional, and nested arrays

Documentation

• Added Exporting-Swift-Array.md covering array usage, supported types, and copy semantics

[kateinoigakukun]

Awesome work, thanks!

Overall it looks good to me. A few things to follow up but we can incubate in the main branch.

1. Missing support for some element types:
   • JSObject
   • @JSClass struct
2. Import-side support
3. Specialized optimization for integer/float Arrays
   • For example, we can use Int32Array for [Int] cloning
4. Code size concern
   • Seems like we are currently generating inline lifting/lowring code
   • We might be able to extract and generalize as a runtime code (in BridgeJSIntrinsics.swift)

[krodak]

@kateinoigakukun thanks for feedback, all the great points. I have WIP for integer / floats optimization, I can add JSObject and @jsclass struct support as well.

I’ll think on and explore code size optimization.

As for import side, I’d skip on it on for now, I haven’t implemented import side type yet, but could take a stab at it given new macro based swift code, but it won’t be my priority over next weeks 🙏

[kateinoigakukun]

No worries, I'll take it over 😉