fix over-eager intersection polygon that ate a curve due to two hits with the perpendicular

docs/TODO_quality.md

@@ -12,8 +12,6 @@
 		- the base geometry in OSM is just wrong... because ways have to be connected at the center lines
 		- one-lane coming off a 4 or 5 lane and going one way... maybe it should be shifted to the other side
 			- that messes up the nice curve later. need to clip, not shift.
-	- o123 is a pretty weird shape, it eats the entire curve
-		- did the second_half stuff mess things up?
 	- o40 has a long cut when merged, why not hit in the middle?
 		- what if we allow intersections between infinite lines for merged cases?
 	- try it bigger

map_model/src/make/initial/geometry.rs

@@ -136,8 +136,9 @@ fn generalized_trim_back(
                 )
                 .infinite();
                 // How could something perpendicular to a shifted polyline never hit the original
-                // polyline?
-                let trim_to = road_center.intersection_infinite(&perp).unwrap();
+                // polyline? Also, find the hit closest to the intersection -- this matters for
+                // very curvy roads, like highway ramps.
+                let trim_to = road_center.reversed().intersection_infinite(&perp).unwrap();
                 let trimmed = road_center.get_slice_ending_at(trim_to).unwrap();
                 if trimmed.length() < shortest_center.length() {
                     shortest_center = trimmed;