Hi,

unless I am missing something, the problem with optimal object construction with user-defined constructor is still unsolved in your proposal.

I.e.

when we have an aggregate:

struct Foo

{

Bar1 a;

Bar2 b;

};

Following expression is optimal w.r.t. construction (no copy/moves for Bar1/Bar2) thanks to aggregate initialization:

Foo f = { Bar1{...}, Bar2{...} }; // #1

But if user-defined constructor is provided, then there is no way to achieve optimal construction with same initialization expression as in #1.

struct Foo

{

Foo(Bar1 a, Bar2 b) #2

: a(std::move(a)), b(std::move(b))

{}

Foo(const Bar&1 a, const Bar2& b) #3

: a(a), b(b)

{}

Bar1 a;

Bar2 b;

};

You get a temporary construction, and either move(#2) or copy(#3) + temporary destruction.

Ultimate copy ellision, should relax rules of copy elision so that any copy/moves of constructor arguments into object members/bases is allowed as well.

So that the most simple constructor definition is always optimal:

struct Foo

{

Foo(Bar1 a, Bar2 b)

: a(a), b(b)

{}

Bar1 a;

Bar2 b;

};

Regards,

Maciej