Open Radar

 
This is a duplicate of rdar://23711954

Summary:
Trying to use a generic objective-c class's type in a generic type of a block parameter works when declaring methods, but not when defining them, but not using them produces a warning about mismatched parameter types. For example:

@interface MyContainer <ObjectType: NSObject *> : NSObject
// Declaring methods works fine:
- (void)foo:(void (^)(MyContainer<ObjectType> *))block;
- (void)bar:(void (^)(MyContainer<ObjectType> *))block;
- (void)baz:(ObjectType)obj;
@end

@implementation MyContainer
// With the generic type:
// error: No type or protocol named 'ObjectType'
// warning: conflicting parameter types in implementation of 'foo:': 'void (^__strong)(MyContainer<ObjectType> *__strong)' vs 'void (^__strong)(MyContainer *__strong)'
- (void)foo:(void (^)(MyContainer<ObjectType> *))block {
    block(self);
}

// Without the generic type:
// warning: conflicting parameter types in implementation of 'bar:': 'void (^__strong)(MyContainer<ObjectType> *__strong)' vs 'void (^__strong)(MyContainer *__strong)'
- (void)bar:(void (^)(MyContainer *))block {
    block(self);
}

// Using NSObject rather than ObjectType does not produce a warning when
// it isn't a block parameter
- (void)baz:(NSObject *)obj {
    (void)obj;
}

Version:
Xcode 8.2 (8C38)