More than one invariant per struct/class

[Alex Rønne Petersen]

On 04-08-2011 11:32, simendsjo wrote:
> I would like to use a template mixin to add some fields to a struct, but
> I'd also like the template to add additional invariant checks without
> having to remember to add this for all struct/classes that mixes in this
> code.
>
> class C {
> int a;
> }
>
> mixin template EmbedC() {
> C _c;
>
> // oops.. more than one invariant
> invariant() {
> assert(_c);
> }
>
> void close() {
> _c = null;
> }
> }
>
> struct S {
> int i = 10;
> invariant() {
> assert(i >= 10);
> }
>
> mixin EmbedC!();
> }
>
> void main() {
> S s;
> s.close();
> s._c.a = 10; // access violation, but I want assertion from invariant
> }

This sounds reasonable and useful to me.

- Alex