Which operators cannot be overloaded and why not?

[user1234]

On Monday, 13 September 2021 at 14:59:38 UTC, Paul Backus wrote:
> On Monday, 13 September 2021 at 14:42:42 UTC, jfondren wrote:
>> On Monday, 13 September 2021 at 14:33:03 UTC, user1234 wrote:
>>> - condition al expression ` cond ? exp : exp `
>>
>> And many other boolean operators, unary !, binary && and ||
>>
>> https://dlang.org/spec/operatoroverloading.html lists all the 
>> overloadable operators, and 
>> https://dlang.org/spec/expression.html has all the operators, 
>> so "which operators" is a matter of close comparison. "why 
>> not" is much harder to answer.
>
> I think the intent is for the boolean operators to be handled 
> via `opCast!bool`.

I didn't see it was already suggested and answered the same... 
but yet that's exactly the case.