Could not build Objective c Module - ios

Question

i was making a xcode project with swift and it was working fine but suddenly it started giving me this error.
Could not build Objective C Module 'Foundation'
/Users/admin/Downloads/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator10.2.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSNotification.h:17:4: Prefix attribute must be followed by an interface or protocol
Even when i create a new project and do nothing but just build it, this error is shown. The project is not built. When i click on the error message, it leads me to this file NSNotification.h
Here are the contents of this file
/* NSNotification.h
Copyright (c) 1994-2016, Apple Inc. All rights reserved.
*/
#import <Foundation/NSObject.h>
typedef NSString *NSNotificationName NS_EXTENSIBLE_STRING_ENUM;
#class NSString, NSDictionary, NSOperationQueue;
NS_ASSUME_NONNULL_BEGIN
/**************** Notifications ****************/
#interface NSNotification : NSObject <NSCopying, NSCoding>
id#property (nullable, readonly, retain) id object;
#property (nullable, readonly, copy) NSDictionary *userInfo;
- (instancetype)initWithName:(NSNotificationName)name object:(nullable id)object userInfo:(nullable NSDictionary *)userInfo NS_AVAILABLE(10_6, 4_0) NS_DESIGNATED_INITIALIZER;
- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder NS_DESIGNATED_INITIALIZER;
#end
#interface NSNotification (NSNotificationCreation)
+ (instancetype)notificationWithName:(NSNotificationName)aName object: (nullable id)anObject;
+ (instancetype)notificationWithName:(NSNotificationName)aName object: (nullable id)anObject userInfo:(nullable NSDictionary *)aUserInfo;
- (instancetype)init /*NSUIImagePNGRepresentation_UNAVAILABLE*/; /* do not invoke; not a valid initializer for this class */
#end
/**************** Notification Center ****************/
#interface NSNotificationCenter : NSObject {
#package
void *_impl;
void *_callback;
void *_pad[11];
}
#if FOUNDATION_SWIFT_SDK_EPOCH_AT_LEAST(8)
#property (class, readonly, strong) NSNotificationCenter *defaultCenter;
- (void)addObserver:(id)observer selector:(SEL)aSelector name:(nullable NSNotificationName)aName object:(nullable id)anObject;
#endif
- (void)postNotification:(NSNotification *)notification;
- (void)postNotificationName:(NSNotificationName)aName object:(nullable id)anObject;
- (void)postNotificationName:(NSNotificationName)aName object:(nullable id)anObject userInfo:(nullable NSDictionary *)aUserInfo;
- (void)removeObserver:(id)observer;
- (void)removeObserver:(id)observer name:(nullable NSNotificationName)aName object:(nullable id)anObject;
- (id <NSObject>)addObserverForName:(nullable NSNotificationName)name object:(nullable id)obj queue:(nullable NSOperationQueue *)queue usingBlock:(void (^)(NSNotification *note))block NS_AVAILABLE(10_6, 4_0);
// The return value is retained by the system, and should be held onto by the caller in
// order to remove the observer with removeObserver: later, to stop observation.
#end
NS_ASSUME_NONNULL_END
Please help me through this. I will be very grateful for this. Thanks.

Answer 1

This line in NSNotification.h looks like it's been modified:
id#property (nullable, readonly, retain) id object;
Delete the id at the front of that line and try to recompile. That should fix it.