arc(ellipse, point, point) doesn't work in non-default coordsys

[jamadagni]

import geometry;
size(10cm, 0);
currentcoordsys = cartesiansystem(i = N, j = W);

point P = (0, 0), Q = (-5, 1);
real v = abs(P - Q);
point R = P + (0, v);  // by def R lies on circle with center P and radius PQ
draw(Q -- P -- R, red + blue);
dot(P, red);
dot(Q ^^ R, blue);
draw(arc(circle(P, v), Q, R), green);
shipout(bbox(0.25cm));

As you can see the arc doesn't connect Q and R. Removing the modification of currentcoordsys, this works. Please advise what is wrong.

[jamadagni]

import geometry;
size(10cm, 0);
currentcoordsys = cartesiansystem(i = N, j = W);

point P = (0, 0);
circle C = circle(P, 5);
point Q = angpoint(C, 90);
point R = angpoint(C, 135);
draw(C);
draw(arc(circle(P, 5), Q, R), green + 2);
dot(P ^^ Q ^^ R);

shipout(bbox(0.25cm));

This doesn't work either.

[jamadagni]

Curiously, adding the coordsys modification to the given example of arc(ellipse, point, point) works. I don't understand why that example should work but my constructed examples don't.

[jamadagni]

In view of issue #333 I think the problem is perhaps with the underlying drawing routine which fails to compensate for rotation of coordinate system because arc(ellipse, point, point) internally seems to just go via arc(ellipse, abscissa, abscissa) to arc(ellipse, angle, angle). But I am not sufficiently confident…