Rollup merge of #95308 - bjorn3:more_stable_proc_macro, r=Mark-Simulacrum

Reduce the amount of unstable features used in libproc_macro

This makes it easier to adapt the source for stable when copying it into rust-analyzer to load rustc compiled proc macros.

library/proc_macro/src/bridge/client.rs

@@ -2,6 +2,8 @@
 
 use super::*;
 
+use std::marker::PhantomData;
+
 macro_rules! define_handles {
     (
         'owned: $($oty:ident,)*
@@ -45,20 +47,25 @@ macro_rules! define_handles {
 
         $(
             #[repr(C)]
-            pub(crate) struct $oty(handle::Handle);
-            impl !Send for $oty {}
-            impl !Sync for $oty {}
+            pub(crate) struct $oty {
+                handle: handle::Handle,
+                // Prevent Send and Sync impls
+                _marker: PhantomData<*mut ()>,
+            }
 
             // Forward `Drop::drop` to the inherent `drop` method.
             impl Drop for $oty {
                 fn drop(&mut self) {
-                    $oty(self.0).drop();
+                    $oty {
+                        handle: self.handle,
+                        _marker: PhantomData,
+                    }.drop();
                 }
             }
 
             impl<S> Encode<S> for $oty {
                 fn encode(self, w: &mut Writer, s: &mut S) {
-                    let handle = self.0;
+                    let handle = self.handle;
                     mem::forget(self);
                     handle.encode(w, s);
                 }
@@ -74,7 +81,7 @@ macro_rules! define_handles {
 
             impl<S> Encode<S> for &$oty {
                 fn encode(self, w: &mut Writer, s: &mut S) {
-                    self.0.encode(w, s);
+                    self.handle.encode(w, s);
                 }
             }
 
@@ -88,7 +95,7 @@ macro_rules! define_handles {
 
             impl<S> Encode<S> for &mut $oty {
                 fn encode(self, w: &mut Writer, s: &mut S) {
-                    self.0.encode(w, s);
+                    self.handle.encode(w, s);
                 }
             }
 
@@ -113,7 +120,10 @@ macro_rules! define_handles {
 
             impl<S> DecodeMut<'_, '_, S> for $oty {
                 fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
-                    $oty(handle::Handle::decode(r, s))
+                    $oty {
+                        handle: handle::Handle::decode(r, s),
+                        _marker: PhantomData,
+                    }
                 }
             }
         )*
@@ -121,13 +131,15 @@ macro_rules! define_handles {
         $(
             #[repr(C)]
             #[derive(Copy, Clone, PartialEq, Eq, Hash)]
-            pub(crate) struct $ity(handle::Handle);
-            impl !Send for $ity {}
-            impl !Sync for $ity {}
+            pub(crate) struct $ity {
+                handle: handle::Handle,
+                // Prevent Send and Sync impls
+                _marker: PhantomData<*mut ()>,
+            }
 
             impl<S> Encode<S> for $ity {
                 fn encode(self, w: &mut Writer, s: &mut S) {
-                    self.0.encode(w, s);
+                    self.handle.encode(w, s);
                 }
             }
 
@@ -149,7 +161,10 @@ macro_rules! define_handles {
 
             impl<S> DecodeMut<'_, '_, S> for $ity {
                 fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
-                    $ity(handle::Handle::decode(r, s))
+                    $ity {
+                        handle: handle::Handle::decode(r, s),
+                        _marker: PhantomData,
+                    }
                 }
             }
         )*
@@ -310,7 +325,8 @@ impl Bridge<'_> {
         // NB. the server can't do this because it may use a different libstd.
         static HIDE_PANICS_DURING_EXPANSION: Once = Once::new();
         HIDE_PANICS_DURING_EXPANSION.call_once(|| {
-            panic::update_hook(move |prev, info| {
+            let prev = panic::take_hook();
+            panic::set_hook(Box::new(move |info| {
                 let show = BridgeState::with(|state| match state {
                     BridgeState::NotConnected => true,
                     BridgeState::Connected(_) | BridgeState::InUse => force_show_panics,
@@ -318,7 +334,7 @@ impl Bridge<'_> {
                 if show {
                     prev(info)
                 }
-            });
+            }));
         });
 
         BRIDGE_STATE.with(|state| state.set(BridgeState::Connected(self), f))

library/proc_macro/src/bridge/closure.rs

@@ -1,24 +1,23 @@
 //! Closure type (equivalent to `&mut dyn FnMut(A) -> R`) that's `repr(C)`.
 
+use std::marker::PhantomData;
+
 #[repr(C)]
 pub struct Closure<'a, A, R> {
-    call: unsafe extern "C" fn(&mut Env, A) -> R,
-    env: &'a mut Env,
+    call: unsafe extern "C" fn(*mut Env, A) -> R,
+    env: *mut Env,
+    // Ensure Closure is !Send and !Sync
+    _marker: PhantomData<*mut &'a mut ()>,
 }
 
-extern "C" {
-    type Env;
-}
-
-impl<'a, A, R> !Sync for Closure<'a, A, R> {}
-impl<'a, A, R> !Send for Closure<'a, A, R> {}
+struct Env;
 
 impl<'a, A, R, F: FnMut(A) -> R> From<&'a mut F> for Closure<'a, A, R> {
     fn from(f: &'a mut F) -> Self {
-        unsafe extern "C" fn call<A, R, F: FnMut(A) -> R>(env: &mut Env, arg: A) -> R {
+        unsafe extern "C" fn call<A, R, F: FnMut(A) -> R>(env: *mut Env, arg: A) -> R {
             (*(env as *mut _ as *mut F))(arg)
         }
-        Closure { call: call::<A, R, F>, env: unsafe { &mut *(f as *mut _ as *mut Env) } }
+        Closure { call: call::<A, R, F>, env: f as *mut _ as *mut Env, _marker: PhantomData }
     }
 }
 

library/proc_macro/src/bridge/mod.rs

@@ -231,10 +231,10 @@ pub struct Bridge<'a> {
 
     /// If 'true', always invoke the default panic hook
     force_show_panics: bool,
-}
 
-impl<'a> !Sync for Bridge<'a> {}
-impl<'a> !Send for Bridge<'a> {}
+    // Prevent Send and Sync impls
+    _marker: marker::PhantomData<*mut ()>,
+}
 
 #[forbid(unsafe_code)]
 #[allow(non_camel_case_types)]

library/proc_macro/src/bridge/server.rs

@@ -153,7 +153,12 @@ impl ExecutionStrategy for SameThread {
         let mut dispatch = |b| dispatcher.dispatch(b);
 
         run_client(
-            Bridge { cached_buffer: input, dispatch: (&mut dispatch).into(), force_show_panics },
+            Bridge {
+                cached_buffer: input,
+                dispatch: (&mut dispatch).into(),
+                force_show_panics,
+                _marker: marker::PhantomData,
+            },
             client_data,
         )
     }
@@ -189,6 +194,7 @@ impl ExecutionStrategy for CrossThread1 {
                     cached_buffer: input,
                     dispatch: (&mut dispatch).into(),
                     force_show_panics,
+                    _marker: marker::PhantomData,
                 },
                 client_data,
             )
@@ -241,6 +247,7 @@ impl ExecutionStrategy for CrossThread2 {
                     cached_buffer: input,
                     dispatch: (&mut dispatch).into(),
                     force_show_panics,
+                    _marker: marker::PhantomData,
                 },
                 client_data,
             );

library/proc_macro/src/lib.rs

@@ -17,18 +17,18 @@
     test(no_crate_inject, attr(deny(warnings))),
     test(attr(allow(dead_code, deprecated, unused_variables, unused_mut)))
 )]
+// This library is copied into rust-analyzer to allow loading rustc compiled proc macros.
+// Please avoid unstable features where possible to minimize the amount of changes necessary
+// to make it compile with rust-analyzer on stable.
 #![feature(rustc_allow_const_fn_unstable)]
 #![feature(nll)]
 #![feature(staged_api)]
 #![feature(allow_internal_unstable)]
 #![feature(decl_macro)]
-#![feature(extern_types)]
 #![feature(negative_impls)]
-#![feature(auto_traits)]
 #![feature(restricted_std)]
 #![feature(rustc_attrs)]
 #![feature(min_specialization)]
-#![feature(panic_update_hook)]
 #![recursion_limit = "256"]
 
 #[unstable(feature = "proc_macro_internals", issue = "27812")]