Disallowing S() when struct S has a constructor

[Paul Backus]

On Friday, 6 September 2024 at 09:45:39 UTC, Quirin Schroll wrote:
> On Thursday, 5 September 2024 at 18:17:33 UTC, Paul Backus 
> wrote:
>> We already have compiler-generated default implementations for 
>> copy constructors and `opAssign`, and neither of them support 
>> this kind of explicit declaration. Why is it necessary to have 
>> this for default constructors, if it wasn't necessary for copy 
>> constructors and `opAssign`?
>
> Because defining any constructor makes the compiler not 
> generate a default constructor. It’s a way to say: Give me the 
> default constructor without spelling it out.

My point is: so far, we have been fine with requiring the 
programmer to spell it out in other cases. Why is that 
unacceptable in this case specifically?

Maybe the answer is, "it's not just a problem in this case, the 
programmer shouldn't have to spell it out in any of those other 
cases either." If so, then this should be a more general language 
feature, with its own DIP separate from any default-constructor 
proposal.