Possible optimization opportunity when assigning to a member in the constructor

[Ali Çehreli]

struct Inner below has an opAssign that gets called in Outer.this even 
with -O. That opAssign call seems unnecessary:

import std.stdio;

struct Inner
{
     int i;

     void opAssign(Inner rhs)
     {
         writeln("moving");
     }
}

struct Outer
{
     Inner inner;

     this(int i)
     {
         writeln("Assigning to this.inner");
         this.inner = Inner(i);
     }
}

void main()
{
     writeln("Constructing main.inner");
     auto inner = Inner(42);

     writeln("Constructing main.outer");
     auto outer = Outer(43);
}

The two lines in main are different from the point of view of two Inners 
in the program: The first one is the construction of an Inner variable. 
The second one is the construction of an Outer variable which happens to 
have an Inner member.

Here is the output of the program:

   Constructing main.inner
   Constructing main.outer
   Assigning to this.inner
   moving

I think the last line should not happen.

Naturally, there is no opAssign called when constructing main.inner. 
However, the assignment to this.inner in the constructor is treated as a 
"move" of the value Inner(i) on top of the value of Inner.init. Although 
there is nothing wrong with that, I think the compiler can simply blit 
Inner(i) to this.inner and doing so would be safe.

Does that make sense? Something like "If an rvalue is assigned to a 
member in a constructor, do not call opAssign() of the member".

Ali