reduce Rc usage in stack

src/rstd/collections/stack.rs

@@ -9,7 +9,7 @@ pub struct StackNode<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> {
     /// Reference comes first due to being inlineable.
     pub rest: Stack<'a, Ctx, A>,
     /// Unlike the original implementation in Python, doesn't default to using Point.
-    pub element: Rc<A>,
+    pub element: A,
 }
 
 /// Type representing a stack, an alias to a [Nullable] of a [StackNode].
@@ -90,17 +90,15 @@ impl<'a, Ctx: Context<'a>, F: Factory<'a, Ctx>> Factory<'a, Ctx> for StackNodeFa
                 return Err(StackParseError::Point(ppe));
             }
         };
-        let element = Rc::new(
-            match self
-                .element_factory
-                .deserialize(deserializer, resolver, addresses)
-            {
-                Ok(element) => element,
-                Err(epe) => {
-                    return Err(StackParseError::Element(epe));
-                }
-            },
-        );
+        let element = match self
+            .element_factory
+            .deserialize(deserializer, resolver, addresses)
+        {
+            Ok(element) => element,
+            Err(epe) => {
+                return Err(StackParseError::Element(epe));
+            }
+        };
         Ok(StackNode { rest, element })
     }
 
@@ -113,9 +111,9 @@ impl<'a, Ctx: Context<'a>, F: Factory<'a, Ctx>> Factory<'a, Ctx> for StackNodeFa
 pub type StackFaiure<'a, Ctx, A> = ResolutionFailure<'a, Ctx, StackNode<'a, Ctx, A>>;
 
 /// See [`StackVecWrapped`].
-pub type StackVecResult<'a, Ctx, A> = Result<Vec<Rc<A>>, StackFaiure<'a, Ctx, A>>;
+pub type StackVecResult<'a, Ctx, A> = Result<Vec<A>, StackFaiure<'a, Ctx, A>>;
 
-/// See [`ExtStack::vec`].
+/// See [`ExtStackClone::vec`].
 pub type StackVecWrapped<'a, Ctx, A> = Wrapped<'a, Ctx, StackVecResult<'a, Ctx, A>>;
 
 /// Extention trait with helper methods for [Stack]s.
@@ -128,6 +126,12 @@ pub trait ExtStack<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>>: Mentionable<'
     ///
     /// Note: consumes the stack. For non-consuming version do `.clone()` before adding.
     fn add(self, element: A) -> Self;
+}
+
+/// Extention trait with helper methods for [Stack]s.
+pub trait ExtStackClone<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone>:
+    Mentionable<'a, Ctx>
+{
     /// Collect all the elements into a [`Vec`].
     fn vec(self) -> StackVecWrapped<'a, Ctx, A>;
 }
@@ -143,11 +147,16 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> ExtStack<'a, Ctx, A> for Sta
         Nullable::NotNull(
             StackNode {
                 rest: self,
-                element: Rc::new(element),
+                element,
             }
             .into(),
         )
     }
+}
+
+impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone> ExtStackClone<'a, Ctx, A>
+    for Stack<'a, Ctx, A>
+{
     fn vec(self) -> StackVecWrapped<'a, Ctx, A> {
         Ctx::T::iterate_mut((vec![], self), |(mut vec, stack)| match stack {
             Nullable::Null(_) => Ctx::pure(ControlFlow::Break(Ok(vec))),