Auto merge of #136965 - jhpratt:rollup-bsnqvmf, r=jhpratt

Rollup of 8 pull requests

Successful merges:

 - #134999 (Add cygwin target.)
 - #136559 (Resolve named regions when reporting type test failures in NLL)
 - #136660 (Use a trait to enforce field validity for union fields + `unsafe` fields + `unsafe<>` binder types)
 - #136858 (Parallel-compiler-related cleanup)
 - #136881 (cg_llvm: Reduce visibility of all functions in the llvm module)
 - #136888 (Always perform discr read for never pattern in EUV)
 - #136948 (Split out the `extern_system_varargs` feature)
 - #136949 (Fix import in bench for wasm)

r? `@ghost`
`@rustbot` modify labels: rollup

2 files changed, 7 insertions, 8 deletions

diff --git a/compiler/rustc_data_structures/src/sync/freeze.rs b/compiler/rustc_data_structures/src/sync/freeze.rs
index 5236c9fe156..9720b22ea7d 100644
--- a/compiler/rustc_data_structures/src/sync/freeze.rs
+++ b/compiler/rustc_data_structures/src/sync/freeze.rs
@@ -3,9 +3,9 @@ use std::intrinsics::likely;
 use std::marker::PhantomData;
 use std::ops::{Deref, DerefMut};
 use std::ptr::NonNull;
-use std::sync::atomic::Ordering;
+use std::sync::atomic::{AtomicBool, Ordering};
 
-use crate::sync::{AtomicBool, DynSend, DynSync, ReadGuard, RwLock, WriteGuard};
+use crate::sync::{DynSend, DynSync, ReadGuard, RwLock, WriteGuard};
 
 /// A type which allows mutation using a lock until
 /// the value is frozen and can be accessed lock-free.
diff --git a/compiler/rustc_data_structures/src/sync/worker_local.rs b/compiler/rustc_data_structures/src/sync/worker_local.rs
index d75af009850..402ec9827bb 100644
--- a/compiler/rustc_data_structures/src/sync/worker_local.rs
+++ b/compiler/rustc_data_structures/src/sync/worker_local.rs
@@ -106,12 +106,6 @@ pub struct WorkerLocal<T> {
     registry: Registry,
 }
 
-// This is safe because the `deref` call will return a reference to a `T` unique to each thread
-// or it will panic for threads without an associated local. So there isn't a need for `T` to do
-// it's own synchronization. The `verify` method on `RegistryId` has an issue where the id
-// can be reused, but `WorkerLocal` has a reference to `Registry` which will prevent any reuse.
-unsafe impl<T: Send> Sync for WorkerLocal<T> {}
-
 impl<T> WorkerLocal<T> {
     /// Creates a new worker local where the `initial` closure computes the
     /// value this worker local should take for each thread in the registry.
@@ -138,6 +132,11 @@ impl<T> Deref for WorkerLocal<T> {
     fn deref(&self) -> &T {
         // This is safe because `verify` will only return values less than
         // `self.registry.thread_limit` which is the size of the `self.locals` array.
+
+        // The `deref` call will return a reference to a `T` unique to each thread
+        // or it will panic for threads without an associated local. So there isn't a need for `T` to do
+        // it's own synchronization. The `verify` method on `RegistryId` has an issue where the id
+        // can be reused, but `WorkerLocal` has a reference to `Registry` which will prevent any reuse.
         unsafe { &self.locals.get_unchecked(self.registry.id().verify()).0 }
     }
 }