TopoGeo_addPoint fails: end node not geometry end point

[strk]

Testcase:

SELECT NULL FROM topology.CreateTopology ('topo');                                                                                                                                             
SELECT NULL FROM topology.TopoGeo_addLinestring('topo', 'LINESTRING(0 0, 5 1, 10 0)');                                                                                                         
SELECT NULL FROM topology.TopoGeo_addPoint('topo', 'POINT(9 5)', 5);       

Results in:

ERROR:  SQL/MM Spatial exception - end node not geometry end point.

PostGIS-3.4 is not affected, this is the code in the experimental edge merging.

[strk]

The problem is that the input point (9 5) is first projected to the existing edge and then the edge is snapped to it, effectively moving its last point.

[strk]

Debug output:

psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_AddPoint:6687] Adding point: POINT(9 5)
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_AddPoint:6763] New point is within 5 units of 1 edges
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_SplitAllEdgesToNewNode:6452] Edge 1 distance: 4.70678724331642
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_SplitAllEdgesToNewNode:6507] Projected point: POINT(8.076923076923077 0.384615384615385)
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_SplitAllEdgesToNewNode:6533] Splitting closest edge 1
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_SplitAllEdgesToNewNode:6543] Edge 1 does not contain projected point to it
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_toposnap:443] It took 1/1 iterations to properly snap
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_SplitAllEdgesToNewNode:6561] Edge snapped with tolerance 5
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_SplitAllEdgesToNewNode:6569] Edge LINESTRING(0 0,5 1,10 0) snapped became LINESTRING(0 0,5 1,8.076923076923077 0.384615384615385)
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_SplitAllEdgesToNewNode:6582] Edge first point is 0 0, snapline first point is 0 0
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:_lwt_SplitAllEdgesToNewNode:6606] Snapping did not move first point
psql:test0.sql:7: DEBUG:  [topo/lwgeom_topo.c:lwt_ChangeEdgeGeom:3308] lwt_ChangeEdgeGeom: old edge has 3 points, new edge has 3 points
psql:test0.sql:7: ERROR:  SQL/MM Spatial exception - end node not geometry end point.

The code only checks for moving first point, not last point.