Struct constructor, opCall mess.

[monarch_dodra]

On Monday, 24 February 2014 at 17:15:10 UTC, Remo wrote:
> So what is proper/best way to mimic default constructor for 
> struct ?

Honestly, you can't, and you shouldn't try either. There "used" 
to be the static opCall that allowed:
----
auto a = T();
----

But:
a) This is being phased out: If T has a constructor, it will 
seize to compile.
b) It's not "default": "T a;" will still compile, but not 
construct.

The feedback I've been getting is that the "correct" way to 
guarantee construction is to do it via a named factory pattern. 
You disable the this(), so as to "force" initialization, and make 
the constructors private. You'll get something along the lines of:

T a; //Nope.
T a = T(); //Nope
T a = T.build(); //OK!
T a = T(1, 2); //Nope!
T a = T.build(1, 2); //OK!
T a = T.init; //OK! Special explicit requrest for 
non-initialisation.

With D's move semantics and (N)RVO, there should be 0 overhead to 
do this.