[ObjC] Mark classes that shouldn't be subclassed as such.

Several of the classes vended by the runtime don't really support subclassing,
so mark them as such to get compiler enforcement just in case.

PiperOrigin-RevId: 505221732

objectivec/GPBArray.h

@@ -48,6 +48,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @note This class is not meant to be subclassed.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBInt32Array : NSObject <NSCopying>
 
 /** The number of elements contained in the array. */
@@ -222,6 +223,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @note This class is not meant to be subclassed.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBUInt32Array : NSObject <NSCopying>
 
 /** The number of elements contained in the array. */
@@ -396,6 +398,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @note This class is not meant to be subclassed.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBInt64Array : NSObject <NSCopying>
 
 /** The number of elements contained in the array. */
@@ -570,6 +573,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @note This class is not meant to be subclassed.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBUInt64Array : NSObject <NSCopying>
 
 /** The number of elements contained in the array. */
@@ -744,6 +748,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @note This class is not meant to be subclassed.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBFloatArray : NSObject <NSCopying>
 
 /** The number of elements contained in the array. */
@@ -918,6 +923,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @note This class is not meant to be subclassed.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBDoubleArray : NSObject <NSCopying>
 
 /** The number of elements contained in the array. */
@@ -1092,6 +1098,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @note This class is not meant to be subclassed.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBBoolArray : NSObject <NSCopying>
 
 /** The number of elements contained in the array. */
@@ -1266,6 +1273,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @note This class is not meant to be subclassed.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBEnumArray : NSObject <NSCopying>
 
 /** The number of elements contained in the array. */
@@ -1583,6 +1591,7 @@ NS_ASSUME_NONNULL_END
 //% *
 //% * @note This class is not meant to be subclassed.
 //% **/
+//%__attribute__((objc_subclassing_restricted))
 //%@interface GPB##NAME##Array : NSObject <NSCopying>
 //%
 //%/** The number of elements contained in the array. */
@@ -1675,6 +1684,7 @@ NS_ASSUME_NONNULL_END
 //% *
 //% * @note This class is not meant to be subclassed.
 //% **/
+//%__attribute__((objc_subclassing_restricted))
 //%@interface GPB##NAME##Array : NSObject <NSCopying>
 //%
 //%/** The number of elements contained in the array. */

objectivec/GPBCodedInputStream.h

@@ -83,6 +83,7 @@ CF_EXTERN_C_END
  *
  * @note Subclassing of @c GPBCodedInputStream is NOT supported.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBCodedInputStream : NSObject
 
 /**

objectivec/GPBCodedOutputStream.h

@@ -63,6 +63,7 @@ extern NSString *const GPBCodedOutputStreamException_WriteFailed;
  *
  * @note Subclassing of GPBCodedOutputStream is NOT supported.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBCodedOutputStream : NSObject
 
 /**

objectivec/GPBDescriptor.h

@@ -62,7 +62,8 @@ typedef NS_ENUM(uint8_t, GPBFieldType) {
 /**
  * Describes a proto message.
  **/
-@interface GPBDescriptor : NSObject <NSCopying>
+__attribute__((objc_subclassing_restricted))
+@interface GPBDescriptor : NSObject<NSCopying>
 
 - (instancetype)init NS_UNAVAILABLE;
 + (instancetype)new NS_UNAVAILABLE;
@@ -124,6 +125,7 @@ typedef NS_ENUM(uint8_t, GPBFieldType) {
 /**
  * Describes a proto file.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBFileDescriptor : NSObject
 
 - (instancetype)init NS_UNAVAILABLE;
@@ -149,6 +151,7 @@ typedef NS_ENUM(uint8_t, GPBFieldType) {
 /**
  * Describes a oneof field.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBOneofDescriptor : NSObject
 
 - (instancetype)init NS_UNAVAILABLE;
@@ -182,6 +185,7 @@ typedef NS_ENUM(uint8_t, GPBFieldType) {
 /**
  * Describes a proto field.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBFieldDescriptor : NSObject
 
 - (instancetype)init NS_UNAVAILABLE;
@@ -234,6 +238,7 @@ typedef NS_ENUM(uint8_t, GPBFieldType) {
 /**
  * Describes a proto enum.
  **/
+__attribute__((objc_subclassing_restricted))
 @interface GPBEnumDescriptor : NSObject
 
 - (instancetype)init NS_UNAVAILABLE;
@@ -329,7 +334,8 @@ typedef NS_ENUM(uint8_t, GPBFieldType) {
 /**
  * Describes a proto extension.
  **/
-@interface GPBExtensionDescriptor : NSObject <NSCopying>
+__attribute__((objc_subclassing_restricted))
+@interface GPBExtensionDescriptor : NSObject<NSCopying>
 
 - (instancetype)init NS_UNAVAILABLE;
 + (instancetype)new NS_UNAVAILABLE;