error : outer function context of `D main` is needed to `new` nested class `main.main.X`

Bert Bert at
Fri Aug 16 21:23:03 UTC 2019

On Thursday, 15 August 2019 at 02:23:06 UTC, Adam D. Ruppe wrote:
> On Thursday, 15 August 2019 at 01:55:17 UTC, Bert wrote:
>> void main()
>> {
>>     class X { ... }
> I would just make it `static class X` and then it should work 
> fine.
> Won't be able to access main's local variables then though, but 
> you could pass the necessary ones through the constructors or 
> something.

That might work, I can't think of the case where I would need to 
access them, although some could exist. It's not a general 
solution though. I've came up with a work around that isn't great 
but seems to work.

So the whole point of this is that the class cannot be 
constructed because a context pointer won't exist outside of 
main? It seems that things were done backwards, the class never 
references anything outside it and for all practical purposes is 
static... seems that all classes should have been default static 
and something like `nonstatic class` should have been required to 
capture the context.

Or better yet, some way to construct the class if is effectively 
a static class to get most use cases and error else rather than 
just scrub all possibilities.

e.g., maybe there could be a way to construct the class 
manually(emplace?) and just use a null context pointer and hope 
for the best or somehow figure out if it requires a context and 
if so then error?

If the outer context can be captured by the function, then it 
could be passed to emplace.

For example, one could pass a delegate and use it's context 
pointer, and as long as it is the same as the context the class 
is defined in, then it should be used?

I am using emplace now to construct the class and it seems to 
work without the error but, of course, the context will be wrong. 
Is there any way to somehow get the context properly? (since 
these things are relatively fixed in code so should the context 
and one should be able to statically reference it with the 
appropriate symbol?)

So basically I can essentially do what I said above with emplace 
but this is error prone without a proper context. I assume that 
when a class is defined, the outer is always the context of where 
the class is defined and not where it is created. If this is 
true, and it should be since it would make no real since other 
wise(unless one was very careful) then one would be able to 
reference that context statically.



should return the context for the class X.

I haven't been able to figure out how to do this though and I 
will just rely on my original workaround for now since it is safe.

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