[Issue 9732] Do not call opAssign() for the first assignment to member in the constructor

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=9732



--- Comment #7 from Maxim Fomin <maxim at maxim-fomin.ru> 2013-03-17 09:21:59 PDT ---
(In reply to comment #3)
> I really don't think that's a problem. If anything, the default value should
> NOT be destroyed in the constructor. After all, it hasn't really even been
> initialized yet.

There are several corner cases when dtor gets default value. By the way, how
you can distinguish whether object was recently initialized to its state was
reseted?

> If anything, that's exactly how "aggregate construction" works: postblit each
> value over the current fields, but DON'T destroy the fields:
> 
> //--------
> import std.stdio;
> 
> struct Inner
> {
>     int i;
>     this(this){} //Postblit implies destruction of this.
>     ~this()
>     {
>         writeln(i);
>     }
> }
> 
> struct Outer
> {
>     Inner inner = Inner(1);    // <-- compile-time .init
> }
> 
> void main()
> {
>     auto inner = Inner(2);
>     {
>         writeln("****");
>         auto outer = Outer(inner); // Overwrite with postblit, but don't call
> destructor.
>         writeln("****");
>     }
>     {
>         writeln("****");
>         auto outer = Outer(inner); // Overwrite with postblit, but don't call
> destructor.
>         outer.inner = inner;       // Call postblit, destroying previous state.
>         writeln("****");
>     }
> }
> //--------
> ****
> **** //Notice no destroyer called here
> 2    //This is outer's destroyer destroying its inner
> ****
> 2    //This is our second blit.
> ****
> 2    //This is out second outer destroyer's destroying its inner
> 2    //This is our inner's destroyer
> //--------
> 
> So yeah, my conclusion is: destroyers are not a problem to this proposal.

I don't how this is related to the issue.

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