Implement a class with mixins

[Frank Benoit]

Does a protected inheritance make sense in a language without multiple
inheritance? Inherit private is for a "implemented with" relation. And
this is perhaps better made with the mixin feature.

But to use mixins like base classes for implementation, mixins are
missing a Ctor ( and DTor ) integration. It should be possible for a
mixin to have a Ctor which is automatically called while the object is
contructed. Or it can be called manually ( with args ) from the class ctor.

.template Foo(){
.  this( int a ){}
.}
.
.template Bar(){
.  this(){}
.}
.
.class C{
.  mixin Foo foo;
.  public this(){
.    foo.this( 2 ); // if missing => compile error
.    // bar.this() is implicit called, manually call is possible
.  }
.}