From 5be3d4bee4f1cdd79b47579c84199a484a09f3e9 Mon Sep 17 00:00:00 2001
From: Pavel Grigorenko <grigorenkopv@ya.ru>
Date: Mon, 19 Feb 2024 17:37:43 +0300
Subject: [PATCH] Remove `RefMutL` hack in `proc_macro::bridge`

---
 library/proc_macro/src/bridge/client.rs      |  7 +------
 library/proc_macro/src/bridge/scoped_cell.rs | 22 ++------------------
 2 files changed, 3 insertions(+), 26 deletions(-)

diff --git a/library/proc_macro/src/bridge/client.rs b/library/proc_macro/src/bridge/client.rs
index 9255c3abc8a02..52b9ef470dccb 100644
--- a/library/proc_macro/src/bridge/client.rs
+++ b/library/proc_macro/src/bridge/client.rs
@@ -296,12 +296,7 @@ impl BridgeState<'_> {
     /// N.B., while `f` is running, the thread-local state
     /// is `BridgeState::InUse`.
     fn with<R>(f: impl FnOnce(&mut BridgeState<'_>) -> R) -> R {
-        BRIDGE_STATE.with(|state| {
-            state.replace(BridgeState::InUse, |mut state| {
-                // FIXME(#52812) pass `f` directly to `replace` when `RefMutL` is gone
-                f(&mut *state)
-            })
-        })
+        BRIDGE_STATE.with(|state| state.replace(BridgeState::InUse, f))
     }
 }
 
diff --git a/library/proc_macro/src/bridge/scoped_cell.rs b/library/proc_macro/src/bridge/scoped_cell.rs
index 2cde1f65adf9c..53eae1ebdb0fb 100644
--- a/library/proc_macro/src/bridge/scoped_cell.rs
+++ b/library/proc_macro/src/bridge/scoped_cell.rs
@@ -2,7 +2,6 @@
 
 use std::cell::Cell;
 use std::mem;
-use std::ops::{Deref, DerefMut};
 
 /// Type lambda application, with a lifetime.
 #[allow(unused_lifetimes)]
@@ -15,23 +14,6 @@ pub trait LambdaL: for<'a> ApplyL<'a> {}
 
 impl<T: for<'a> ApplyL<'a>> LambdaL for T {}
 
-// HACK(eddyb) work around projection limitations with a newtype
-// FIXME(#52812) replace with `&'a mut <T as ApplyL<'b>>::Out`
-pub struct RefMutL<'a, 'b, T: LambdaL>(&'a mut <T as ApplyL<'b>>::Out);
-
-impl<'a, 'b, T: LambdaL> Deref for RefMutL<'a, 'b, T> {
-    type Target = <T as ApplyL<'b>>::Out;
-    fn deref(&self) -> &Self::Target {
-        self.0
-    }
-}
-
-impl<'a, 'b, T: LambdaL> DerefMut for RefMutL<'a, 'b, T> {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        self.0
-    }
-}
-
 pub struct ScopedCell<T: LambdaL>(Cell<<T as ApplyL<'static>>::Out>);
 
 impl<T: LambdaL> ScopedCell<T> {
@@ -46,7 +28,7 @@ impl<T: LambdaL> ScopedCell<T> {
     pub fn replace<'a, R>(
         &self,
         replacement: <T as ApplyL<'a>>::Out,
-        f: impl for<'b, 'c> FnOnce(RefMutL<'b, 'c, T>) -> R,
+        f: impl for<'b, 'c> FnOnce(&'b mut <T as ApplyL<'c>>::Out) -> R,
     ) -> R {
         /// Wrapper that ensures that the cell always gets filled
         /// (with the original state, optionally changed by `f`),
@@ -71,7 +53,7 @@ impl<T: LambdaL> ScopedCell<T> {
             })),
         };
 
-        f(RefMutL(put_back_on_drop.value.as_mut().unwrap()))
+        f(put_back_on_drop.value.as_mut().unwrap())
     }
 
     /// Sets the value in `self` to `value` while running `f`.