How do I check if a type is assignable to null at compile time?

[Jack]

On Friday, 26 February 2021 at 05:45:39 UTC, Nathan S. wrote:
> On Friday, 26 February 2021 at 05:34:26 UTC, Paul Backus wrote:
>> On Friday, 26 February 2021 at 05:25:14 UTC, Jack wrote:
>>> I started with:
>>>
>>> enum isAssignableNull(T) = is(T : Object) || isPointer(T);
>>>
>>> but how do I cover all cases?
>>
>> Something like this should work:
>>
>> enum isAssignableNull(T) = __traits(compiles, (T t) => t = 
>> null);
>
> `isAssignableNull!(immutable void*)` is true with his 
> definition but false with yours. Of course you are correct that 
> you cannot assign to an immutable pointer.

yep, it must be true for pointers too. Thank you all guys.  
is(typeof(null) : T) works like a charm