Specifying @nogc on structs seems to have no effect

[Craig Black]

On Wednesday, 20 September 2017 at 02:43:44 UTC, B4s1L3 wrote:
> On Tuesday, 19 September 2017 at 13:11:03 UTC, Craig Black 
> wrote:
>> I've recently tried coding in D again after some years.  One 
>> of my earlier concerns was the ability to code without the GC, 
>> which seemed difficult to pull off.  To be clear, I want my 
>> programs to be garbage collected, but I want to use the GC 
>> sparingly so that the mark and sweep collections will be fast.
>>  So I want guarantees that certain sections of code and 
>> certain structs will not require the GC in any way.
>>
>> I realize that you can allocate on the non-GC heap using 
>> malloc and free and emplace, but I find it troubling that you 
>> still need to tell the GC to scan your allocation. What I 
>> would like is, for example, to be able to write a @nogc 
>> templated struct that guarantees that none of its members 
>> require GC scanning.  Thus:
>>
>> @nogc struct Array(T)
>> {
>>   ...
>> }
>>
>> class GarbageCollectedClass
>> {
>> }
>>
>> void main()
>> {
>>   Array!int intArray; // fine
>>
>>
>> }
>
> I've implemented data annotation in iz, if you want to take a 
> look.
> It's quite near from what you descibed in a more recent answer:
>
> ----
> /+ dub.sdl:
>    name "dub_script"
>    dependency "iz" version="0.6.0"
> +/
> module dub_script;
>
> import iz.memory;
>
> // defines a class that has a member
> // which is usually handled by the GC
> class Foo {void* looks_gc_managed;}
> // defines a class and marks member as nogc-"trusted"
> class Bar {@NoGc Foo foo;}
> // defines a class without annotation
> class Baz {Foo foo;}
>
> // verified statically
> static assert(!MustAddGcRange!Bar);
> static assert( MustAddGcRange!Baz);
>
> void main(string[] args)
> {
>     Foo foo = construct!Foo;
>     destruct(foo);
> }
> ----
>
> It's another way of doing things. It's less strict than 
> checking all the functions.
>
> note: the script can be run directly by passing the file to DUB 
> (single file package).

Wow!  Yeah that seems like almost exactly what I want. Sorry what 
is iz?  Thank you!

-Craig