Specifying @nogc on structs seems to have no effect

[John Colvin]

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
>
>
> }

@nogc has nothing to do with whether something needs scanning. It 
guarantees that code will never allocate with the GC or trigger a 
GC collection (because the only way to do that is to allocate or 
to call the functions in core.memory.GC, which are deliberately 
not marked @nogc).