Re: Doubt about alias this

[Phil Lavoie]

Hi,

I tested the code you provided and extended it a little and here 
is the result:

struct bar (bool B, N...) {
 int n = 0;
}

struct foo (N...) {
 bar!(true, N) _bar = void;

 bar!(true, N) getN() {
   return _bar;
 }

 alias getN this;

 public this(T) (T other)
   if (is(T unused : int)) {
   n = other;
 }
}

void aFunc( bar!( true, 8 ) zeBar ) {
  //Subtyping compiles.
}

bar!( true, 8 ) aSecondFunc() {
  return bar!( true, 8 )();
}

struct toto{
  size_t payload;
}

toto aThirdFunc() {
  return toto();
}

void main() {
 import std.stdio;
 foo!8 a = 42;
 writeln(a.n); //Prints 0, as it should.
 aFunc( a ); //The alias this correctly allows for subtyping, as 
advertised
 a.getN().n = 3; //Allowing for rvalue manipulation is indeed 
weird, but apparently in a coherent fashion, not just for the 
alias this case.
 writeln(a.n); //Still prints 0, as it should.
 aSecondFunc().n = 4;
 aThirdFunc().payload = 10; //Without alias this, without 
templates, juste plain rvalue. Another coherent example, yet 
questionably permitted.
}

Therefore, your question, I believe, is more related to rvalues 
directly rather than alias this, if I get your meaning right. The 
question is still very relevant and I was surprised to find out 
about the current behaviors of rvalues.