Add ReverseCurveCoordinateSystems::Reversed

This is preparation for some other changes to make the trait more
flexible.

crates/fj-core/src/operations/reverse/cycle.rs

@@ -34,7 +34,12 @@ impl Reverse for Cycle {
 }
 
 impl ReverseCurveCoordinateSystems for Cycle {
-    fn reverse_curve_coordinate_systems(&self, core: &mut Core) -> Self {
+    type Reversed = Cycle;
+
+    fn reverse_curve_coordinate_systems(
+        &self,
+        core: &mut Core,
+    ) -> Self::Reversed {
         let edges = self
             .half_edges()
             .iter()

crates/fj-core/src/operations/reverse/face.rs

@@ -43,7 +43,12 @@ impl<const D: usize> Reverse for Polygon<D, IsInsertedYes> {
 }
 
 impl ReverseCurveCoordinateSystems for Face {
-    fn reverse_curve_coordinate_systems(&self, core: &mut Core) -> Self {
+    type Reversed = Face;
+
+    fn reverse_curve_coordinate_systems(
+        &self,
+        core: &mut Core,
+    ) -> Self::Reversed {
         let region = self
             .region()
             .reverse_curve_coordinate_systems(core)

crates/fj-core/src/operations/reverse/half_edge.rs

@@ -8,7 +8,12 @@ use crate::{
 use super::ReverseCurveCoordinateSystems;
 
 impl ReverseCurveCoordinateSystems for Handle<HalfEdge> {
-    fn reverse_curve_coordinate_systems(&self, core: &mut Core) -> Self {
+    type Reversed = Handle<HalfEdge>;
+
+    fn reverse_curve_coordinate_systems(
+        &self,
+        core: &mut Core,
+    ) -> Self::Reversed {
         let mut half_edge_geom = *core.layers.geometry.of_half_edge(self);
         half_edge_geom.path = half_edge_geom.path.reverse();
         half_edge_geom.boundary = half_edge_geom.boundary.reverse();

crates/fj-core/src/operations/reverse/mod.rs

@@ -16,9 +16,15 @@ pub trait Reverse {
 
 /// Reverse the direction of the curve coordinate systems within an object
 pub trait ReverseCurveCoordinateSystems {
+    /// The type of the reversed object
+    type Reversed;
+
     /// Reverse the direction of the curve coordinate systems within an object
     ///
     /// This will not have any effect on object positions in global coordinates.
     #[must_use]
-    fn reverse_curve_coordinate_systems(&self, core: &mut Core) -> Self;
+    fn reverse_curve_coordinate_systems(
+        &self,
+        core: &mut Core,
+    ) -> Self::Reversed;
 }

crates/fj-core/src/operations/reverse/region.rs

@@ -22,7 +22,12 @@ impl Reverse for Region {
 }
 
 impl ReverseCurveCoordinateSystems for Region {
-    fn reverse_curve_coordinate_systems(&self, core: &mut Core) -> Self {
+    type Reversed = Region;
+
+    fn reverse_curve_coordinate_systems(
+        &self,
+        core: &mut Core,
+    ) -> Self::Reversed {
         let exterior = self
             .exterior()
             .reverse_curve_coordinate_systems(core)