Error: TypeInfo.equals is not implemented

[Andre]

Hi,

I do not understand the following error message. I have template 
structure Decimal, which is used in a OrderDb structure.

Comparing two OrderDb structures is working, but trying to compare
two OrderDb array structures ends with an error message:
object.Error: TypeInfo.equals is not implemented.

Kind regards
André

--- Code ---

import std.traits: isInstanceOf;

struct Decimal(int precision, int scale){
        bool opEquals(T)(T d)
                if (isInstanceOf!(Decimal, T))
        {
                return false;
        }
}

struct OrderDb{
        string orderId;
        Decimal!(10,2) amount;
}

void main(){
        auto o1 = OrderDb();
        auto o2 = OrderDb();
        if (o1 == o2) {}; // Works
        if ([o1] == [o2]) {}; // object.Error: TypeInfo.equals is not 
implemented
}