Conflicting parameter types in implementation of 'executorWithBlock'

Question

Honestly I'm new to Xcode and I have no idea what this means? I'm guessing it's a problem with the code being redundant. I've attempted to remove a few areas of this code but I'm still receiving errors.

Here is the code:

+ (instancetype)executorWithBlock: (void(^)(void(^block)(void))) block {
    return [[self alloc] initWithBlock:block];
}

this is the warning message:

Conflicting parameter types in implementation of executorWithBlock:: void (^ _Nonnull __strong)(void (^ _Nonnull __strong)()) vs void (^ _Nonnull __strong)(void (^ _Nonnull __strong)(void))