contracts: Fix R-tree envelope invariance test

Violations were not detected if shape changed but not the envelope
(which is the case when bends are flipped).

src/layout.rs

@@ -316,10 +316,13 @@ impl Layout {
 impl Layout {
     fn test_envelopes(&self) -> bool {
         !self.rtree.iter().any(|wrapper| {
+            let index = wrapper.data;
+            let shape = untag!(index, Primitive::new(index, &self.graph).shape());
+            let wrapper = RTreeWrapper::new(shape, index);
             !self
                 .rtree
-                .locate_in_envelope(&wrapper.geom().envelope())
-                .any(|w| w == wrapper)
+                .locate_in_envelope(&shape.envelope())
+                .any(|w| *w == wrapper)
         })
     }
 }

src/shape.rs

@@ -69,7 +69,7 @@ impl BendShape {
     }
 }
 
-#[derive(Debug, EnumAsInner, PartialEq)]
+#[derive(Debug, Clone, Copy, EnumAsInner, PartialEq)]
 pub enum Shape {
     // Intentionally in different order to reorder `self.intersects(...)` properly.
     Dot(DotShape),