refactor: change Visitable to use static dispatch instead

This option was not available when this macro was written. Making this change can have a small performance improvement. BREAKING CHANGE: This may break in functions which received the `visitor` via an argument that expect a dynamic visitor.
chesedo · Aug 12, 2024 · 05f7439 · 05f7439
1 parent 43d62b8
commit 05f7439
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Showing 9 changed files with 49 additions and 46 deletions.
diff --git a/despatma/src/lib.rs b/despatma/src/lib.rs
@@ -307,7 +307,7 @@ pub fn interpolate_traits(tokens: TokenStream, concrete_impl: TokenStream) -> To
 /// Creates an abstract visitor for a list of elements.
 ///
 /// This macro does three things:
-/// 1. A `Visitor` trait is created with methods to visit each element. Each method calls a default helper function by default.
+/// 1. A `Visitor` trait is created with methods to visit each element in the list. Each method calls a default helper function by default (see point 2).
 /// 1. A helper function is created for each element. The idea is for this function to traverse into the elements children.
 /// 1. A `Visitable` trait is created that redirects / reflects each element back to its visitor
 ///
@@ -338,7 +338,7 @@ pub fn interpolate_traits(tokens: TokenStream, concrete_impl: TokenStream) -> To
 /// ```
 ///
 /// ## Output
-/// The three elements listed above will be created.
+/// The three sets of things listed earlier will be created.
 /// ```
 /// use despatma::visitor;
 ///
@@ -371,20 +371,20 @@ pub fn interpolate_traits(tokens: TokenStream, concrete_impl: TokenStream) -> To
 /// }
 ///
 /// trait Visitable {
-///     fn apply(&self, visitor: &mut dyn Visitor);
+///     fn apply(&self, visitor: &mut impl Visitor);
 /// }
 /// impl Visitable for Arc {
-///     fn apply(&self, visitor: &mut dyn Visitor) {
+///     fn apply(&self, visitor: &mut impl Visitor) {
 ///         visitor.visit_arc(self);
 ///     }
 /// }
 /// impl Visitable for Rectangle {
-///     fn apply(&self, visitor: &mut dyn Visitor) {
+///     fn apply(&self, visitor: &mut impl Visitor) {
 ///         visitor.visit_rectangle(self);
 ///     }
 /// }
 /// impl Visitable for Point {
-///     fn apply(&self, visitor: &mut dyn Visitor) {
+///     fn apply(&self, visitor: &mut impl Visitor) {
 ///         visitor.visit_point(self);
 ///     }
 /// }
@@ -405,7 +405,7 @@ pub fn interpolate_traits(tokens: TokenStream, concrete_impl: TokenStream) -> To
 /// }
 /// ```
 ///
-/// The input shows `Visitor` can be applied to structs (`Rectangle`) and traits (`Arc` and `Point`).
+/// The input shows `Visitor` can be applied to structs, but the macro also supports traits.
 ///
 /// ## Usage
 /// Any visitor can now just implement the `Visitor` trait and provide its own implementation for any of the visitor methods.
@@ -438,6 +438,9 @@ pub fn interpolate_traits(tokens: TokenStream, concrete_impl: TokenStream) -> To
 /// }
 ///
 /// impl Visitor for PointCounter {
+///     // Only override the visit_point method
+///     // All other methods will call the default helper function since we don't care about those type.
+///     // But we still need to call the helper function to keep the traversal intact.
 ///     fn visit_point(&mut self, point: &Point) {
 ///         self.count += 1;
 ///

diff --git a/despatma/src/visitor.rs b/despatma/src/visitor.rs
@@ -22,7 +22,7 @@ use syn::{Ident, Token};
 /// Thus, it takes a list of types that will be visited.
 /// A type can be concrete or dynamic.
 ///
-/// Options can also be passed to type:
+/// Options can also be passed to the type:
 /// - `no_default` to turn-off the defualt implementation for the trait method.
 /// - 'helper_tmpl` to be filled into the helper template for traversing a types internal structure.
 #[cfg_attr(test, derive(Eq, PartialEq, Debug))]
@@ -93,7 +93,7 @@ impl VisitorFunction {
             // Make visitable
             visitables.push(quote! {
                 impl Visitable for #elem_type {
-                    fn apply(&self, visitor: &mut dyn Visitor) {
+                    fn apply(&self, visitor: &mut impl Visitor) {
                         visitor.#fn_name(self);
                     }
                 }
@@ -109,7 +109,7 @@ impl VisitorFunction {
             #(#helpers)*
 
             trait Visitable {
-                fn apply(&self, visitor: &mut dyn Visitor);
+                fn apply(&self, visitor: &mut impl Visitor);
             }
             #(#visitables)*
         }
@@ -246,7 +246,7 @@ mod tests {
         });
         input.types.push(parse_quote! {
            #[helper_tmpl = {
-               visitor.visit_button(window.button);
+               visitor.visit_button(&window.button);
            }]
            Window
         });
@@ -273,24 +273,24 @@ mod tests {
             where
                 V: Visitor + ?Sized,
             {
-               visitor.visit_button(window.button);
+               visitor.visit_button(&window.button);
             }
 
             trait Visitable {
-                fn apply(&self, visitor: &mut dyn Visitor);
+                fn apply(&self, visitor: &mut impl Visitor);
             }
             impl Visitable for Button {
-                fn apply(&self, visitor: &mut dyn Visitor) {
+                fn apply(&self, visitor: &mut impl Visitor) {
                     visitor.visit_button(self);
                 }
             }
             impl Visitable for dyn Text {
-                fn apply(&self, visitor: &mut dyn Visitor) {
+                fn apply(&self, visitor: &mut impl Visitor) {
                     visitor.visit_text(self);
                 }
             }
             impl Visitable for Window {
-                fn apply(&self, visitor: &mut dyn Visitor) {
+                fn apply(&self, visitor: &mut impl Visitor) {
                     visitor.visit_window(self);
                 }
             }

diff --git a/despatma/tests/expand/visitor/complex.expanded.rs b/despatma/tests/expand/visitor/complex.expanded.rs
@@ -12,14 +12,14 @@ pub fn visit_arc<V>(visitor: &mut V, arc: &dyn Arc)
 where
     V: Visitor + ?Sized,
 {
-    visitor.visit_point(arc.center);
+    visitor.visit_point(&arc.center);
 }
 pub fn visit_rectangle<V>(visitor: &mut V, rectangle: &Rectangle)
 where
     V: Visitor + ?Sized,
 {
-    visitor.visit_point(rectangle.top_left);
-    visitor.visit_point(rectangle.bottom_right);
+    visitor.visit_point(&rectangle.top_left);
+    visitor.visit_point(&rectangle.bottom_right);
 }
 pub fn visit_point<V>(_visitor: &mut V, _point: &dyn Point)
 where
@@ -30,25 +30,25 @@ where
     V: Visitor + ?Sized,
 {}
 trait Visitable {
-    fn apply(&self, visitor: &mut dyn Visitor);
+    fn apply(&self, visitor: &mut impl Visitor);
 }
 impl Visitable for dyn Arc {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_arc(self);
     }
 }
 impl Visitable for Rectangle {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_rectangle(self);
     }
 }
 impl Visitable for dyn Point {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_point(self);
     }
 }
 impl Visitable for dyn Circle {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_circle(self);
     }
 }
diff --git a/despatma/tests/expand/visitor/complex.rs b/despatma/tests/expand/visitor/complex.rs
@@ -3,16 +3,16 @@ use despatma::visitor;
 
 visitor!(
     #[
-        helper_tmpl = {visitor.visit_point(arc.center);},
+        helper_tmpl = {visitor.visit_point(&arc.center);},
         no_default,
     ]
     dyn Arc,
 
     #[
         no_default,
         helper_tmpl = {
-            visitor.visit_point(rectangle.top_left);
-            visitor.visit_point(rectangle.bottom_right);
+            visitor.visit_point(&rectangle.top_left);
+            visitor.visit_point(&rectangle.bottom_right);
         },
     ]
     Rectangle,

diff --git a/despatma/tests/expand/visitor/helper_tmpl.expanded.rs b/despatma/tests/expand/visitor/helper_tmpl.expanded.rs
@@ -21,28 +21,28 @@ pub fn visit_rectangle<V>(visitor: &mut V, rectangle: &Rectangle)
 where
     V: Visitor + ?Sized,
 {
-    visitor.visit_point(rectangle.top_left);
-    visitor.visit_point(rectangle.bottom_right);
+    visitor.visit_point(&rectangle.top_left);
+    visitor.visit_point(&rectangle.bottom_right);
 }
 pub fn visit_point<V>(_visitor: &mut V, _point: &Point)
 where
     V: Visitor + ?Sized,
 {}
 trait Visitable {
-    fn apply(&self, visitor: &mut dyn Visitor);
+    fn apply(&self, visitor: &mut impl Visitor);
 }
 impl Visitable for dyn Arc {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_arc(self);
     }
 }
 impl Visitable for Rectangle {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_rectangle(self);
     }
 }
 impl Visitable for Point {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_point(self);
     }
 }
diff --git a/despatma/tests/expand/visitor/helper_tmpl.rs b/despatma/tests/expand/visitor/helper_tmpl.rs
@@ -6,8 +6,8 @@ visitor!(
     dyn Arc,
 
     #[helper_tmpl = {
-        visitor.visit_point(rectangle.top_left);
-        visitor.visit_point(rectangle.bottom_right);
+        visitor.visit_point(&rectangle.top_left);
+        visitor.visit_point(&rectangle.bottom_right);
     }]
     Rectangle,
 

diff --git a/despatma/tests/expand/visitor/multiple.expanded.rs b/despatma/tests/expand/visitor/multiple.expanded.rs
@@ -38,30 +38,30 @@ where
     V: Visitor + ?Sized,
 {}
 trait Visitable {
-    fn apply(&self, visitor: &mut dyn Visitor);
+    fn apply(&self, visitor: &mut impl Visitor);
 }
 impl Visitable for dyn Circle {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_circle(self);
     }
 }
 impl Visitable for Rectangle {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_rectangle(self);
     }
 }
 impl Visitable for dyn Sphere {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_sphere(self);
     }
 }
 impl Visitable for Arc {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_arc(self);
     }
 }
 impl Visitable for dyn Cube {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_cube(self);
     }
 }
diff --git a/despatma/tests/expand/visitor/no_default.expanded.rs b/despatma/tests/expand/visitor/no_default.expanded.rs
@@ -13,15 +13,15 @@ where
     V: Visitor + ?Sized,
 {}
 trait Visitable {
-    fn apply(&self, visitor: &mut dyn Visitor);
+    fn apply(&self, visitor: &mut impl Visitor);
 }
 impl Visitable for dyn Button {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_button(self);
     }
 }
 impl Visitable for Window {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_window(self);
     }
 }
diff --git a/despatma/tests/expand/visitor/simple.expanded.rs b/despatma/tests/expand/visitor/simple.expanded.rs
@@ -10,10 +10,10 @@ where
     V: Visitor + ?Sized,
 {}
 trait Visitable {
-    fn apply(&self, visitor: &mut dyn Visitor);
+    fn apply(&self, visitor: &mut impl Visitor);
 }
 impl Visitable for Window {
-    fn apply(&self, visitor: &mut dyn Visitor) {
+    fn apply(&self, visitor: &mut impl Visitor) {
         visitor.visit_window(self);
     }
 }