import win32.directx.d3dx9 : D3DXVECTOR2;
import win32.windows : POINT;

struct DVector2
{
	// Controls that the argument is one of the following types: float, DVector2, D3DXVECTOR2, POINT
	template Accepts(T) { enum Accepts = is(T == DVector2) || is(T == float) || is(T == D3DXVECTOR2) || is(T == POINT); }
	
	// Whether the argument is a float or not
 	template isScalar(T) { enum isScalar = is(T == float); }
	
	// X and Y Axis
	float x = 0f, y = 0f;
	
	// Default Constructor
	this()(float x, float y)
	{
		this.x = x;
		this.y = y;
	}
	
	// Implement D3DXVECTOR2 and POINT support
	this(T)(T arg) if(Accepts!T)
	{
		static if(isScalar!T)
			this(arg, arg);
		else
			this(arg.tupleof); // Error: constructor call must be in a constructor
	}
	
	// Binary Operations
	DVector2 opBinary(string op, T)(T rhs) if(Accepts!T)
	{
		enum rx = isScalar!T ? "" : ".x";
		enum ry = isScalar!T ? "" : ".y";
		
		return DVector2(mixin("x" ~ op ~ "rhs" ~ rx), mixin("y" ~ op ~ "rhs" ~ ry));
	}
	
	// Right Binary Operator
	DVector2 opBinaryRight(string op, T)(T lhs) if(Accepts!T)
	{
		return DVector2(lhs).opBinary!op(this); // Error: template instance vector.DVector2.__ctor!(DVector2) error instantiating
	}
	
	// Assign Operator
	ref DVector2 opAssign(T)(T rhs) if(Accepts!T)
	{
		static if(isScalar!T)
			x = y = rhs;
			
		else
		{
			x = rhs.x;
			y = rhs.y;
		}
		
		return this;
	}
}

void main(string[] args)
{
	DVector2 test = DVector2(0f, 1f);
	
	// This statement leads to the following errors:
	// (L28) Error: constructor call must be in a constructor
	// (L43) Error: template instance vector.DVector2.__ctor!(DVector2) error instantiating
	// (L70) Error: instantiated from here: opBinaryRight!("+", DVector2)
	test = test + DVector2(2f, 1f); // Error: instantiated from here: opBinaryRight!("+", DVector2)
}