http://d.puremagic.com/issues/show_bug.cgi?id=9732
monarchdo...@gmail.com changed:
What |Removed |Added
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CC| |monarchdo...@gmail.com
--- Comment #3 from monarchdo...@gmail.com 2013-03-17 07:14:20 PDT ---
(In reply to comment #2)
> I think you are right because the .init state of a member may not be as simple
> as one thinks. Although OuterStruct.inner must be known at compile time, it
> may
> have a non-trivial destructor that needs to be called:
>
> struct Inner
> {
> ~this()
> {
> // ... not-trivial destructor ...
> }
>
> // ...
> }
>
> struct OuterStruct
> {
> Inner inner = Inner(specialInitValue); // <-- compile-time .init
>
> this(int i)
> {
> this.inner = Inner(i); // <-- further assignment
> }
> }
>
> Blitting the rvalue on top of OuterStruct.inner would not be right in that
> case.
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.
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.
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