Instantiation of nested structs should be allowed outside their parent scope

[Timon Gehr]

On 09.11.21 16:36, Timon Gehr wrote:
> On 09.11.21 16:30, Stanislav Blinov wrote:
>>
>> ```d
>> template isNothrowCopyable(To, From)
>> if (is(immutable To == immutable From))
>> {
>>      enum bool isNothrowCopyable = is(typeof((ref scope From from) 
>> nothrow { union U { To to; } U u = U(from); }));
>> }
>> ```
>>
>> ...but it indeed doesn't work for nested structs. And a thing that 
>> does "work" has to reimplement compiler's copy semantics, including 
>> field-by-field blitting, calling constructors and postblits, etc.
> 
> template isNothrowCopyable(To, From)
> if (is(immutable To == immutable From))
> {
>      enum bool isNothrowCopyable = is(typeof((ref scope From from) 
> nothrow { union U { auto to=To.init; } U u = U(from); }));
> }

(I don't know if that solves your problem, as I don't actually have an 
example where your implementation does not work.)