gcc/testsuite/objc.dg/lookup-1.m

/* { dg-do run } */
/* { dg-xfail-run-if "Needs OBJC2 ABI" { *-*-darwin* && { lp64 && { ! objc2 } } } { "-fnext-runtime" } { "" } } */

#include <stdlib.h>
#include "../objc-obj-c++-shared/TestsuiteObject.m"

typedef struct MyWidget {
  int a;
} MyWidget;

MyWidget gWidget = { 17 };

@protocol MyProto
- (MyWidget *)widget;
@end

@interface Foo: TestsuiteObject
@end

@interface Bar: Foo <MyProto>
@end

@interface Container: TestsuiteObject
+ (MyWidget *)elementForView:(Foo *)view;
@end

@implementation Foo
@end

@implementation Bar
- (MyWidget *)widget {
  return &gWidget;
}
@end

@implementation Container
+ (MyWidget *)elementForView:(Foo *)view
{
  MyWidget *widget = (MyWidget *) nil;
  if (class_conformsToProtocol (object_getClass (view),
				@protocol(MyProto))) {
    widget = [(Foo <MyProto> *)view widget];
  }
  return widget;
}
@end

int main(void) {
  id view = [Bar new];
  MyWidget *w = [Container elementForView: view];

  if (!w || w->a != 17)
    abort ();

  return 0;
}