From 97beb5028f7b3b550c1b25345347b0b29fb5d3c7 Mon Sep 17 00:00:00 2001
From: Anders Kaseorg <andersk@mit.edu>
Date: Sun, 18 Dec 2022 19:37:37 -0800
Subject: [PATCH] Remove Trace implementation for Rc
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I’m not sure if these impls would work with a better tracing
algorithm, but they do not work correctly with this one.

    let r = Rc::new(Gc::new(()));
    Gc::new((Rc::clone(&r), r));
    // → thread 'main' panicked at 'Can't double-unroot a Gc<T>'

Fixes #134.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
---
 gc/src/trace.rs        | 16 ----------------
 gc/tests/trace_impl.rs |  5 -----
 2 files changed, 21 deletions(-)

diff --git a/gc/src/trace.rs b/gc/src/trace.rs
index c881bfc..816c3fe 100644
--- a/gc/src/trace.rs
+++ b/gc/src/trace.rs
@@ -237,22 +237,6 @@ type_arg_tuple_based_finalize_trace_impls![
     (A, B, C, D, E, F, G, H, I, J, K, L);
 ];
 
-impl<T: Trace + ?Sized> Finalize for Rc<T> {}
-unsafe impl<T: Trace + ?Sized> Trace for Rc<T> {
-    custom_trace!(this, {
-        mark(&**this);
-    });
-}
-
-impl<T: Trace> Finalize for Rc<[T]> {}
-unsafe impl<T: Trace> Trace for Rc<[T]> {
-    custom_trace!(this, {
-        for e in this.iter() {
-            mark(e);
-        }
-    });
-}
-
 impl<T: Trace + ?Sized> Finalize for Box<T> {}
 unsafe impl<T: Trace + ?Sized> Trace for Box<T> {
     custom_trace!(this, {
diff --git a/gc/tests/trace_impl.rs b/gc/tests/trace_impl.rs
index c59783f..9840133 100644
--- a/gc/tests/trace_impl.rs
+++ b/gc/tests/trace_impl.rs
@@ -46,11 +46,6 @@ struct InnerRcStr {
     inner: Rc<str>,
 }
 
-#[derive(Trace, Clone, Finalize)]
-struct InnerRcStruct {
-    inner: Rc<Bar>,
-}
-
 #[derive(Trace, Finalize)]
 struct Baz {
     a: Bar,