Rollup merge of #131866 - jieyouxu:thread_local, r=jhpratt

Avoid use imports in `thread_local_inner!`

Previously, the use imports in `thread_local_inner!` can shadow user-provided types or type aliases of the names `Storage`, `EagerStorage`, `LocalStorage` and `LocalKey`. This PR fixes that by dropping the use imports and instead refer to the std-internal types via fully qualified paths. A basic test is added to ensure `thread_local!`s with static decls with type names that match the aforementioned std-internal type names can successfully compile.

Fixes #131863.

2 files changed, 26 insertions, 22 deletions

diff --git a/library/std/src/sys/thread_local/native/mod.rs b/library/std/src/sys/thread_local/native/mod.rs
index f498dee0899..a5dffe3c458 100644
--- a/library/std/src/sys/thread_local/native/mod.rs
+++ b/library/std/src/sys/thread_local/native/mod.rs
@@ -49,20 +49,21 @@ pub use lazy::Storage as LazyStorage;
 #[unstable(feature = "thread_local_internals", issue = "none")]
 #[rustc_macro_transparency = "semitransparent"]
 pub macro thread_local_inner {
-    // used to generate the `LocalKey` value for const-initialized thread locals
+    // NOTE: we cannot import `LocalKey`, `LazyStorage` or `EagerStorage` with a `use` because that
+    // can shadow user provided type or type alias with a matching name. Please update the shadowing
+    // test in `tests/thread.rs` if these types are renamed.
+
+    // Used to generate the `LocalKey` value for const-initialized thread locals.
     (@key $t:ty, const $init:expr) => {{
         const __INIT: $t = $init;
 
         unsafe {
-            use $crate::mem::needs_drop;
-            use $crate::thread::LocalKey;
-            use $crate::thread::local_impl::EagerStorage;
-
-            LocalKey::new(const {
-                if needs_drop::<$t>() {
+            $crate::thread::LocalKey::new(const {
+                if $crate::mem::needs_drop::<$t>() {
                     |_| {
                         #[thread_local]
-                        static VAL: EagerStorage<$t> = EagerStorage::new(__INIT);
+                        static VAL: $crate::thread::local_impl::EagerStorage<$t>
+                            = $crate::thread::local_impl::EagerStorage::new(__INIT);
                         VAL.get()
                     }
                 } else {
@@ -84,21 +85,19 @@ pub macro thread_local_inner {
         }
 
         unsafe {
-            use $crate::mem::needs_drop;
-            use $crate::thread::LocalKey;
-            use $crate::thread::local_impl::LazyStorage;
-
-            LocalKey::new(const {
-                if needs_drop::<$t>() {
+            $crate::thread::LocalKey::new(const {
+                if $crate::mem::needs_drop::<$t>() {
                     |init| {
                         #[thread_local]
-                        static VAL: LazyStorage<$t, ()> = LazyStorage::new();
+                        static VAL: $crate::thread::local_impl::LazyStorage<$t, ()>
+                            = $crate::thread::local_impl::LazyStorage::new();
                         VAL.get_or_init(init, __init)
                     }
                 } else {
                     |init| {
                         #[thread_local]
-                        static VAL: LazyStorage<$t, !> = LazyStorage::new();
+                        static VAL: $crate::thread::local_impl::LazyStorage<$t, !>
+                            = $crate::thread::local_impl::LazyStorage::new();
                         VAL.get_or_init(init, __init)
                     }
                 }
diff --git a/library/std/src/sys/thread_local/os.rs b/library/std/src/sys/thread_local/os.rs
index 26ce3322a16..f5a2aaa6c6a 100644
--- a/library/std/src/sys/thread_local/os.rs
+++ b/library/std/src/sys/thread_local/os.rs
@@ -15,19 +15,24 @@ pub macro thread_local_inner {
         $crate::thread::local_impl::thread_local_inner!(@key $t, { const INIT_EXPR: $t = $init; INIT_EXPR })
     },
 
-    // used to generate the `LocalKey` value for `thread_local!`
+    // NOTE: we cannot import `Storage` or `LocalKey` with a `use` because that can shadow user
+    // provided type or type alias with a matching name. Please update the shadowing test in
+    // `tests/thread.rs` if these types are renamed.
+
+    // used to generate the `LocalKey` value for `thread_local!`.
     (@key $t:ty, $init:expr) => {{
         #[inline]
         fn __init() -> $t { $init }
 
+        // NOTE: this cannot import `LocalKey` or `Storage` with a `use` because that can shadow
+        // user provided type or type alias with a matching name. Please update the shadowing test
+        // in `tests/thread.rs` if these types are renamed.
         unsafe {
-            use $crate::thread::LocalKey;
-            use $crate::thread::local_impl::Storage;
-
             // Inlining does not work on windows-gnu due to linking errors around
             // dllimports. See https://github.com/rust-lang/rust/issues/109797.
-            LocalKey::new(#[cfg_attr(windows, inline(never))] |init| {
-                static VAL: Storage<$t> = Storage::new();
+            $crate::thread::LocalKey::new(#[cfg_attr(windows, inline(never))] |init| {
+                static VAL: $crate::thread::local_impl::Storage<$t>
+                    = $crate::thread::local_impl::Storage::new();
                 VAL.get(init, __init)
             })
         }