Re: auto ref and arrays

[Dan]

On Tuesday, 27 November 2012 at 22:09:21 UTC, Jack Applegame 
wrote:
I don't understand why auto ref doesn't work with arrays.
void test1(T)(auto ref const T[] val) {}
void test2(T)(auto ref const T val) {}
void main() {
  int b;
  test2(b); // OK
  string a;
  test1(a); // Error: cast(const(char[]))a is not an lvalue
}

Since a is mutable itself, compiler uses ref storage class.
cast(const(char[]))a isn't an lvalue, so it's impossible to 
pass it by ref.

But cast(const int)b isn't an lvalue too. Why it's no errors in 
this case?

I thought with auto ref you dispense with the const since it 
figures it out.
The below seems to work.

Thanks,
Dan

import std.traits;
import std.stdio;

void test1(T)(auto ref T val) if(!isArray!T) {
  writeln("Nonarray ", typeid(typeof(val)));
}
void test1(T)(auto ref T val) if(isArray!T) {
  writeln("Array ", typeid(typeof(val)));
}

void main() {
  string a;
  const(string) b = "string that never changes";
  test1(a);
  test1(b);

  int[] x;
  test1(x);
  int y;
  test1(y);
}