oc block 防止 strong capture需要这么写？

afnetworking 中曾有这样一段代码，是维护者防止block强持有 task对象做的修改

__weak __typeof__(task) weakTask = task;
[self.uploadProgress setCancellationHandler:^{
        __typeof__(weakTask) strongTask = weakTask;
        [strongTask cancel];
    }];

这里叫个真，想知道block中是否__typeof__(task) strongTask = weakTask;会导致task 被强持有，于是做了如下测试：
测试类

#import <Foundation/Foundation.h>

@interface BlockClass : NSObject
@property (nonatomic,copy) void (^blockName)();
@end
#import "BlockClass.h"

@implementation BlockClass

- (void)dealloc
{
    NSLog(@"%s", __FUNCTION__);
}

@end

test case模拟 client

#import <XCTest/XCTest.h>
#import "BlockClass.h"

@interface BlockClassTests : XCTestCase
@property (nonatomic,strong) BlockClass *blockObj;
@end

@implementation BlockClassTests

- (void)setUp {
    [super setUp];
    // Put setup code here. This method is called before the invocation of each test method in the class.
     BlockClass *blockObj = [[BlockClass alloc] init];
    __weak typeof(blockObj) weakObj = blockObj;
    blockObj.blockName = ^{
        __strong typeof(blockObj) strongObj = weakObj;
//        id obj = blockObj;//我是注释 2
    };
    self.blockObj = blockObj;
}

- (void)tearDown {
    // Put teardown code here. This method is called after the invocation of each test method in the class.
    [super tearDown];
    self.blockObj = nil;
}

- (void)testExample {
    // This is an example of a functional test case.
    // Use XCTAssert and related functions to verify your tests produce the correct results.
    XCTAssertTrue(self.blockObj.blockName != nil);
}

@end

查证，控制台会输出

2017-08-05 16:57:09.345 OperationQueueTest[26460:10245855] -[BlockClass dealloc]

倘若将注释2 打开，则会导致强持有了。

我的结论是

block中写__typeof__(task) strongTask = weakTask;不会导致task 被强持有。如有问题还望指正。