Swiftgen code crashing after return of class in method that returns NSObject

[tarrinneal]

This swift input

class EmptyClassBridge: NSObject {}

@objc func echoObject() -> NSObject? {
        return EmptyClassBridge()
}

which ffigen makes into

  objc.NSObject? echoObject() {
    objc.checkOsVersionInternal(
      'NIHostIntegrationCoreApiSetup.echoObject',
      iOS: (false, (13, 0, 0)),
      macOS: (false, (16, 0, 0)),
    );
    final $ret = _objc_msgSend_151sglz(object$.ref.pointer, _sel_echoObject);
    return $ret.address == 0
        ? null
        : objc.NSObject.fromPointer($ret, retain: true, release: true);
  }

and

late final _class_EmptyClassBridge = objc.getClass(
  "test_plugin.EmptyClassBridge",
);
late final _sel_isKindOfClass_ = objc.registerName("isKindOfClass:");
final _objc_msgSend_19nvye5 = objc.msgSendPointer
    .cast<
      ffi.NativeFunction<
        ffi.Bool Function(
          ffi.Pointer<objc.ObjCObjectImpl>,
          ffi.Pointer<objc.ObjCSelector>,
          ffi.Pointer<objc.ObjCObjectImpl>,
        )
      >
    >()
    .asFunction<
      bool Function(
        ffi.Pointer<objc.ObjCObjectImpl>,
        ffi.Pointer<objc.ObjCSelector>,
        ffi.Pointer<objc.ObjCObjectImpl>,
      )
    >();
typedef instancetype = ffi.Pointer<objc.ObjCObjectImpl>;
typedef Dartinstancetype = objc.ObjCObject;
late final _sel_init = objc.registerName("init");
final _objc_msgSend_151sglz = objc.msgSendPointer
    .cast<
      ffi.NativeFunction<
        ffi.Pointer<objc.ObjCObjectImpl> Function(
          ffi.Pointer<objc.ObjCObjectImpl>,
          ffi.Pointer<objc.ObjCSelector>,
        )
      >
    >()
    .asFunction<
      ffi.Pointer<objc.ObjCObjectImpl> Function(
        ffi.Pointer<objc.ObjCObjectImpl>,
        ffi.Pointer<objc.ObjCSelector>,
      )
    >();
late final _sel_new = objc.registerName("new");
late final _sel_allocWithZone_ = objc.registerName("allocWithZone:");
final _objc_msgSend_1cwp428 = objc.msgSendPointer
    .cast<
      ffi.NativeFunction<
        ffi.Pointer<objc.ObjCObjectImpl> Function(
          ffi.Pointer<objc.ObjCObjectImpl>,
          ffi.Pointer<objc.ObjCSelector>,
          ffi.Pointer<objc.NSZone>,
        )
      >
    >()
    .asFunction<
      ffi.Pointer<objc.ObjCObjectImpl> Function(
        ffi.Pointer<objc.ObjCObjectImpl>,
        ffi.Pointer<objc.ObjCSelector>,
        ffi.Pointer<objc.NSZone>,
      )
    >();
late final _sel_alloc = objc.registerName("alloc");

/// Generated bridge class from Pigeon that moves data from Swift to Objective-C.
///
/// iOS: introduced 13.0.0
/// macOS: introduced 16.0.0
extension type EmptyClassBridge._(objc.ObjCObject object$)
    implements objc.ObjCObject, objc.NSObject {
  /// Constructs a [EmptyClassBridge] that points to the same underlying object as [other].
  EmptyClassBridge.as(objc.ObjCObject other) : object$ = other {
    objc.checkOsVersionInternal(
      'EmptyClassBridge',
      iOS: (false, (13, 0, 0)),
      macOS: (false, (16, 0, 0)),
    );
    assert(isA(object$));
  }

  /// Constructs a [EmptyClassBridge] that wraps the given raw object pointer.
  EmptyClassBridge.fromPointer(
    ffi.Pointer<objc.ObjCObjectImpl> other, {
    bool retain = false,
    bool release = false,
  }) : object$ = objc.ObjCObject(other, retain: retain, release: release) {
    objc.checkOsVersionInternal(
      'EmptyClassBridge',
      iOS: (false, (13, 0, 0)),
      macOS: (false, (16, 0, 0)),
    );
    assert(isA(object$));
  }

  /// Returns whether [obj] is an instance of [EmptyClassBridge].
  static bool isA(objc.ObjCObject obj) => _objc_msgSend_19nvye5(
    obj.ref.pointer,
    _sel_isKindOfClass_,
    _class_EmptyClassBridge,
  );

  /// alloc
  static EmptyClassBridge alloc() {
    final $ret = _objc_msgSend_151sglz(_class_EmptyClassBridge, _sel_alloc);
    return EmptyClassBridge.fromPointer($ret, retain: false, release: true);
  }

  /// allocWithZone:
  static EmptyClassBridge allocWithZone(ffi.Pointer<objc.NSZone> zone) {
    final $ret = _objc_msgSend_1cwp428(
      _class_EmptyClassBridge,
      _sel_allocWithZone_,
      zone,
    );
    return EmptyClassBridge.fromPointer($ret, retain: false, release: true);
  }

  /// new
  static EmptyClassBridge new$() {
    final $ret = _objc_msgSend_151sglz(_class_EmptyClassBridge, _sel_new);
    return EmptyClassBridge.fromPointer($ret, retain: false, release: true);
  }

  /// Returns a new instance of EmptyClassBridge constructed with the default `new` method.
  EmptyClassBridge() : this.as(new$().object$);
}

extension EmptyClassBridge$Methods on EmptyClassBridge {
  /// init
  EmptyClassBridge init() {
    objc.checkOsVersionInternal(
      'EmptyClassBridge.init',
      iOS: (false, (2, 0, 0)),
      macOS: (false, (10, 0, 0)),
    );
    final $ret = _objc_msgSend_151sglz(
      object$.ref.retainAndReturnPointer(),
      _sel_init,
    );
    return EmptyClassBridge.fromPointer($ret, retain: false, release: true);
  }
}

crashes after return EmptyClassBridge()

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[test_plugin.EmptyClassBridge data]: unrecognized selector sent to instance 0x600000018f60'

[tarrinneal]

If I change the return type to EmptyClassBridge, it works. If I use a return type that is a list or more complex class than this, it also fails.

[liamappelbe]

Trying to repro this ATM. Is echoObject supposed to be a top level function, or a method on a class? If I use the input code as written I get this error from the swift compiler:

/Users/liama/dev/native/pkgs/swiftgen/test/integration/regress_2871.swift:5:2: error: @objc can only be used with members of classes, @objc protocols, and concrete extensions of classes
3 | class EmptyClassBridge: NSObject {}
4 |
5 | @objc func echoObject() -> NSObject? {
  |  `- error: @objc can only be used with members of classes, @objc protocols, and concrete extensions of classes
6 |   return EmptyClassBridge()
7 | }

When I make the function a static method on a util class, and add public and @objc annotations, my test passes:

import Foundation

@objc public class TestEmptyClass: NSObject {}

@objc public class TestFuncs: NSObject {
  @objc public static func echoObject() -> NSObject? {
    return TestEmptyClass()
  }
}

---

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[test_plugin.EmptyClassBridge data]: unrecognized selector sent to instance 0x600000018f60'

This error is suspicious. It looks like it's trying to call a method or load a field called data, but the class is empty. @tarrinneal is there another version of this class that has a data member? Maybe the bindings are out of date?

[tarrinneal]

Sorry, the input method is in a class:

@objc class NIAllNullableTypesBridge: NSObject {
  @objc public func echoObject() -> NSObject? {
    return TestEmptyClass()
  }
}

There have been a few iterations of this example in my code, but none of them had a data member. I can send you my branch to peruse if that will help

[tarrinneal]

It's also possible that it's related to this issue: #2873 since I did have to force some version overrides to get the published version to work at all.

[liamappelbe]

I can send you my branch to peruse if that will help

Yep, that would be helpful. I want to properly trace that data member invocation. I think that's the most suspicious bit.

[tarrinneal]

I think I found the issue, and it's probably not with your code... Closing for now