buffer returns invalid geometries when used with asymmetric distances on the same side

[andre.meyer@…]

Using buffer with distances (2/-1) or (-1/2) should generate a polygon that lies beside the original linestring.

But, since the direction is only determined for both sides (in buffer_inserter, checking negative() for the distance strategy, which returns only true if both sides are negative), the inner of both sides is calculated wrong.

Maybe buffer_inserter could check nageative() for each side separately, and only reverse one side before stitching both sides together?

[anonymous]

red is input linestring, yellow resulting buffer