Fix some SurfaceVertex duplication issues

crates/fj-kernel/src/algorithms/sweep/edge.rs

@@ -169,7 +169,9 @@ impl Sweep for (HalfEdge, Color) {
                 // Need to compare surface forms here, as the global forms might
                 // be coincident when sweeping circles, despite the vertices
                 // being different!
-                if prev_last.surface_form() != next_first.surface_form() {
+                if prev_last.surface_form().id()
+                    != next_first.surface_form().id()
+                {
                     edges[j] = edges[j].clone().reverse();
                 }
 

crates/fj-kernel/src/algorithms/sweep/vertex.rs

@@ -92,33 +92,25 @@ impl Sweep for (Vertex, Handle<Surface>) {
             )
         };
 
-        // And now the vertices. Again, nothing wild here.
-        let vertices = {
-            // Can be cleaned up, once `zip` is stable:
-            // https://doc.rust-lang.org/std/primitive.array.html#method.zip
-            let [a_surface, b_surface] = points_surface;
-            let [a_global, b_global] = vertices_global;
-            let vertices_surface =
-                [(a_surface, a_global), (b_surface, b_global)].map(
-                    |(point_surface, vertex_global)| {
-                        SurfaceVertex::new(
-                            point_surface,
-                            surface.clone(),
-                            vertex_global,
-                            objects,
-                        )
-                    },
-                );
-
-            vertices_surface.map(|surface_form| {
-                Vertex::new(
-                    [surface_form.position().v],
-                    curve.clone(),
-                    surface_form,
-                )
-            })
+        let vertices_surface = {
+            let [_, position] = points_surface;
+            let [_, global_form] = vertices_global;
+
+            [
+                vertex.surface_form().clone(),
+                SurfaceVertex::new(position, surface, global_form, objects),
+            ]
         };
 
+        // And now the vertices. Again, nothing wild here.
+        let vertices = vertices_surface.map(|surface_form| {
+            Vertex::new(
+                [surface_form.position().v],
+                curve.clone(),
+                surface_form,
+            )
+        });
+
         // And finally, creating the output `Edge` is just a matter of
         // assembling the pieces we've already created.
         HalfEdge::new(vertices, edge_global)

crates/fj-kernel/src/partial/objects/cycle.rs

@@ -163,13 +163,40 @@ impl PartialCycle {
     pub fn build(self, objects: &Objects) -> Cycle {
         let surface = self.surface.expect("Need surface to build `Cycle`");
         let surface_for_edges = surface.clone();
-        let half_edges = self.half_edges.into_iter().map(|half_edge| {
-            half_edge
-                .update_partial(|half_edge| {
-                    half_edge.with_surface(Some(surface_for_edges.clone()))
-                })
-                .into_full(objects)
-        });
+        let half_edges = {
+            let (half_edges, _) = self.half_edges.into_iter().fold(
+                (Vec::new(), None),
+                |(mut half_edges, previous), next| {
+                    let previous_half_edge: Option<HalfEdge> = previous;
+
+                    let previous_vertex = previous_half_edge.map(|half_edge| {
+                        let [_, vertex] = half_edge.vertices().clone();
+                        vertex.surface_form().clone()
+                    });
+
+                    let next = next
+                        .update_partial(|half_edge| {
+                            let [from, _] = half_edge.vertices.clone();
+                            let from = from.map(|vertex| {
+                                vertex.update_partial(|partial| {
+                                    partial.with_surface_form(previous_vertex)
+                                })
+                            });
+
+                            half_edge
+                                .with_surface(Some(surface_for_edges.clone()))
+                                .with_from_vertex(from)
+                        })
+                        .into_full(objects);
+
+                    half_edges.push(next.clone());
+
+                    (half_edges, Some(next))
+                },
+            );
+
+            half_edges
+        };
 
         Cycle::new(surface, half_edges)
     }