[Issue 19631] Segfault on simple nested templated struct

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19631

--- Comment #3 from Arne Marschall <bestellung at marschall-informatik.de> ---
(In reply to Basile-z from comment #2)
> Problem happens when the initializer type is being determined. 
> In case of this issue is blocking some work there are two possible
> workarounds in addition to the "non nesting" solution.
> 
> 1. Field!(w, h) a = *new Field!(w, h);
> 2. bool[_h][_w] s = void;  

Actually this is not a blocker, I am only training myself. So I ported this
"Game of Life" example and experimented with different arrays. The templated
version crashed it.

This would work as well
 Field!(w, h) a;
But the complete code uses two instances of Field, a & b and swaps them a lot.
Swapping of a and b is done much faster if they are pointers instead of 100x100
arrays.

This version compiles as well and takes advantage of the internal pointers
within dynamic arrays.

auto ab = [Field!(w, h).init, Field!(w, h).init];

instead of a and b it uses ab[0] and ab ab[1].
And swaps them here.
import std.algorithm.mutation : swap;
swap(ab[0], ab[1]);

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