Assert failure in AddRightEdges() (similar to reported in #72?)

[wrmorris-google]

I've found another failure similar to what I reported in #72. Here's a minimal input set that produces this error, which is an assert failure in sweep.c:AddRightEdges() (but this time it's an assert relating to the winding number)

assert( regPrev->windingNumber - e->winding == reg->windingNumber );

with call stack:
sweep.c:AddRightEdges
sweep.c:SweepEvent
sweep.c:ComputeInterior
tess.c:tessTesselate

The test case that produces this assertion failure:

  TESStesselator* libtess = tessNewTess(nullptr);
  const int kSize = 2;
  const int kStride = kSize * sizeof(float);
  float contour_1[] = {
      -1.0934316, 0.6718408,   //
      -1.0224961, 0.6719364,   //
      -0.8962616, 0.79851276,  //
      -0.9317774, 0.8339327,   //
  };
  tessSetOption(libtess, TESS_REVERSE_CONTOURS, 0);
  tessAddContour(libtess, kSize, contour_1, kStride,
                 sizeof(contour_1) / sizeof(float) / 2);

  float contour_2[] = {
      -1.0934275, 0.6718371,   //
      -1.1465579, 0.6185637,   //
      4.8087187,  -5.320729,   //
      4.8618493,  -5.2674556,  //
  };
  tessSetOption(libtess, TESS_REVERSE_CONTOURS, 1);
  tessAddContour(libtess, kSize, contour_2, kStride,
                 sizeof(contour_2) / sizeof(float) / 2);

  float contour_3[] = {
      -0.044983167, -0.3736277,   //
      -0.09811407,  -0.42690045,  //
      4.8087497,    -5.320695,    //
      4.861881,     -5.267422,    //
  };
  tessSetOption(libtess, TESS_REVERSE_CONTOURS, 1);
  tessAddContour(libtess, kSize, contour_3, kStride,
                 sizeof(contour_3) / sizeof(float) / 2);

  float contour_4[] = {
      -0.044942975, -0.37370682,  //
      -0.09807353,  -0.42697996,  //
      4.808758,     -5.3206916,   //
      4.8618884,    -5.2674184,   //
  };
  tessSetOption(libtess, TESS_REVERSE_CONTOURS, 1);
  tessAddContour(libtess, kSize, contour_4, kStride,
                 sizeof(contour_4) / sizeof(float) / 2);

  float contour_5[] = {
      -0.0449009,  -0.3737888,   //
      -0.09803118, -0.42706218,  //
      4.8087616,   -5.320684,    //
      4.8618917,   -5.2674108,   //
  };
  tessSetOption(libtess, TESS_REVERSE_CONTOURS, 1);
  tessAddContour(libtess, kSize, contour_5, kStride,
                 sizeof(contour_5) / sizeof(float) / 2);

  float contour_6[] = {
      -0.044857033, -0.37371138,  //
      -0.097987816, -0.42698428,  //
      4.8087854,    -5.32066,     //
      4.861916,     -5.267387,    //
  };
  tessSetOption(libtess, TESS_REVERSE_CONTOURS, 1);
  tessAddContour(libtess, kSize, contour_6, kStride,
                 sizeof(contour_6) / sizeof(float) / 2);

  float contour_7[] = {
      -0.044842396, -0.37368622,  //
      -0.097973324, -0.42695898,  //
      4.808791,     -5.320654,    //
      4.861922,     -5.267381,    //
  };
  tessSetOption(libtess, TESS_REVERSE_CONTOURS, 1);
  tessAddContour(libtess, kSize, contour_7, kStride,
                 sizeof(contour_7) / sizeof(float) / 2);

  float normal[] = {0.0f, 0.0f, 1.0f};
  tessTesselate(libtess, TESS_WINDING_POSITIVE, TESS_POLYGONS,
                /*polySize=*/3, /*vertexSize=*/2, normal);
  tessDeleteTess(libtess);

Sorry about the size of the input set - if any of these are removed, no failure occurs.

I've not looked into this further. Any ideas?