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
}