From 708665cebba8ef4b21c30cd71841b6309885347c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?H=C3=A9ctor=20Ram=C3=B3n=20Jim=C3=A9nez?= <hector@hecrj.dev>
Date: Mon, 5 Feb 2024 00:15:35 +0100
Subject: [PATCH] Use `TypeId` to identify `subscription::Map`

---
 futures/src/subscription.rs | 37 +++++++++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/futures/src/subscription.rs b/futures/src/subscription.rs
index 7163248dc8..4d5a119293 100644
--- a/futures/src/subscription.rs
+++ b/futures/src/subscription.rs
@@ -10,6 +10,7 @@ use crate::{BoxStream, MaybeSend};
 
 use futures::channel::mpsc;
 use futures::never::Never;
+use std::any::TypeId;
 use std::hash::Hash;
 
 /// A stream of runtime events.
@@ -88,7 +89,10 @@ impl<Message> Subscription<Message> {
     }
 
     /// Transforms the [`Subscription`] output with the given function.
-    pub fn map<A>(mut self, f: fn(Message) -> A) -> Subscription<A>
+    pub fn map<A>(
+        mut self,
+        f: impl Fn(Message) -> A + MaybeSend + Clone + 'static,
+    ) -> Subscription<A>
     where
         Message: 'static,
         A: 'static,
@@ -97,8 +101,9 @@ impl<Message> Subscription<Message> {
             recipes: self
                 .recipes
                 .drain(..)
-                .map(|recipe| {
-                    Box::new(Map::new(recipe, f)) as Box<dyn Recipe<Output = A>>
+                .map(move |recipe| {
+                    Box::new(Map::new(recipe, f.clone()))
+                        as Box<dyn Recipe<Output = A>>
                 })
                 .collect(),
         }
@@ -143,27 +148,39 @@ pub trait Recipe {
     fn stream(self: Box<Self>, input: EventStream) -> BoxStream<Self::Output>;
 }
 
-struct Map<A, B> {
+struct Map<A, B, F>
+where
+    F: Fn(A) -> B + 'static,
+{
+    id: TypeId,
     recipe: Box<dyn Recipe<Output = A>>,
-    mapper: fn(A) -> B,
+    mapper: F,
 }
 
-impl<A, B> Map<A, B> {
-    fn new(recipe: Box<dyn Recipe<Output = A>>, mapper: fn(A) -> B) -> Self {
-        Map { recipe, mapper }
+impl<A, B, F> Map<A, B, F>
+where
+    F: Fn(A) -> B + 'static,
+{
+    fn new(recipe: Box<dyn Recipe<Output = A>>, mapper: F) -> Self {
+        Map {
+            id: TypeId::of::<F>(),
+            recipe,
+            mapper,
+        }
     }
 }
 
-impl<A, B> Recipe for Map<A, B>
+impl<A, B, F> Recipe for Map<A, B, F>
 where
     A: 'static,
     B: 'static,
+    F: Fn(A) -> B + 'static + MaybeSend,
 {
     type Output = B;
 
     fn hash(&self, state: &mut Hasher) {
+        self.id.hash(state);
         self.recipe.hash(state);
-        self.mapper.hash(state);
     }
 
     fn stream(self: Box<Self>, input: EventStream) -> BoxStream<Self::Output> {