Error: template cannot deduce function from argument types.

[Damian Day via Digitalmars-d-learn]

Hi, I've been trying to reduce a bug in the containers (8824).

 From the example below it seems the dup method is passing the 
constructor
an array of dchars and the template is failing.

Is this a compiler bug, or ?

import std.range, std.traits;

struct Array2(T)
{
     private T[] _payload;

     size_t insertAt(R)(size_t index, R rng)
         if (isInputRange!R && 
isImplicitlyConvertible!(ElementType!R, T))
     {
         return 0;
     }

     this(U)(U[] values...)
         if (isImplicitlyConvertible!(U, T))
     {
         insertAt(0, values);
     }

     @property Array2 dup()
     {
         return Array2(_payload);
     }
}

unittest
{
     Array2!int a; //passes
     Array2!char a; //fails
}