r209906 - Objective-C. Diagnose assigning a block pointer type to

[Jordan Rose]

Our implementation currently does, but I don't think that's guaranteed, publicly documented (other than our libobjc being open-source), or something people should be relying on.

Jordan


On May 30, 2014, at 11:06 , Argyrios Kyrtzidis <kyrtzidis at apple.com> wrote:

> I’m mainly asking if blocks are implicitly implementing the NSObject protocol or not, for example this seems to work:
> 
> typedef void(^blk)(void);
> 
> int main() {
> 	blk b = ^{};
> 	BOOL res = [b respondsToSelector:@selector(retain)];
> 	printf("res: %d\n", res);
> 	return 0;
> }
> 
> 
>> On May 30, 2014, at 11:03 AM, Jordan Rose <jordan_rose at apple.com> wrote:
>> 
>> I think I agree with Fariborz on this one. I don't remember us ever promising that blocks implement the NSObject protocol, just that they are valid Objective-C objects and that they implement -retain, -release, and -copy. The spec on the Clang site doesn't even promise -retain. (http://clang.llvm.org/docs/BlockLanguageSpec.html#objective-c-extensions)
>> 
>> The developer can always cast if they really need this.
>> 
>> Jordan
>> 
>> 
>> On May 30, 2014, at 10:49 , jahanian <fjahanian at apple.com> wrote:
>> 
>>> It makes no sense to assign block to an object conforming to protocols.
>>> Such objects must implement methods of those protocols which  blocks cannot.
>>> I explicitly ruled this out. Did you see this in an actual user code? Curious to see how it is being used.
>>> 
>>> - Fariborz
>>> 
>>> On May 30, 2014, at 10:32 AM, Argyrios Kyrtzidis <kyrtzidis at apple.com> wrote:
>>> 
>>>> This is giving an error in the following case, is this correct ?
>>>> 
>>>> #import <Foundation/Foundation.h>
>>>> 
>>>> typedef void(^blk)(void);
>>>> 
>>>> void foo(blk b) {
>>>> 	id<NSObject> x = b; // error: initializing 'id<NSObject>' with an expression of incompatible type 'blk' (aka 'void (^)(void)')
>>>> }
>>>> 
>>> 
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>> 
>