RustString produces "Nonisolated deinitializer 'deinit'" error

[kshehata]

I'm trying to follow the instructions in the book to get started with swift-bridge. I'm not sure if this is a new thing in Swift, but I'm getting the following error:

[...]/ios-rust-analyzer/IosRustAnalyzer/SwiftBridgeCore.swift:874:5: Nonisolated deinitializer 'deinit' has different actor isolation from main actor-isolated overridden declaration

I've gotten past this error just by adding the "isolate" keyword to the deinit. I don't know if that's the right solution, since I'm new to all of this, but the result looks like:

public class RustString: RustStringRefMut {
    var isOwned: Bool = true

    public override init(ptr: UnsafeMutableRawPointer) {
        super.init(ptr: ptr)
    }

    isolated deinit {
        if isOwned {
            __swift_bridge__$RustString$_free(ptr)
        }
    }
}

[kahnclusions]

I'm getting this too, just following the instructions in the book, no idea why this happens

[kshehata]

@kahnclusions I'm guessing it's a change in Swift that hasn't been handled in swift-bridge. If you make the change above you should be able to get it to work.

[kahnclusions]

You're right @kshehata, previously everything is nonisolated by default, but as of XCode 26 (and Swift 6) the default settings have changed so that things are main actor-isolated by default.

There is a similar issue open for UniFFI: mozilla/uniffi-rs#2818

As a temporary workaround I've adapted that sed line into my build-rust.sh to make the generated declarations nonisolated for now, but I think swift-bridge should be adapted to output correct code for Swift 6. (cc @chinedufn ). I'm still wrapping my head around Swift's isolation / nonisolated rules so I'm not sure what is the best way forward for the generated code.

add_nonisolated_if_missing() {
  local file="$1"

  if [[ ! -f "$file" ]]; then
    echo "File not found: $file" >&2
    return 1
  fi

  if ! grep -q '\bnonisolated\b' "$file"; then
    sed -i '' \
      -e 's/^fileprivate /nonisolated fileprivate /' \
      -e 's/^private /nonisolated private /' \
      -e 's/^public /nonisolated public /' \
      -e 's/^open /nonisolated open /' \
      -e 's/^extension /nonisolated extension /' \
      "$file"
  fi
}
add_nonisolated_if_missing MyProject/Generated/SwiftBridgeCore.swift
add_nonisolated_if_missing MyProject/Generated/my-rust-bridge/my-rust-bridge.swift