From fc75a4e14607a9b6445fd0c6685fb6999fa69de8 Mon Sep 17 00:00:00 2001
From: Nikolai Vazquez <hello@nikolaivazquez.com>
Date: Tue, 3 Oct 2023 14:44:41 -0400
Subject: [PATCH 1/3] Allow any expression blocks in `thread_local!`

---
 library/std/src/thread/local.rs | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/library/std/src/thread/local.rs b/library/std/src/thread/local.rs
index 338567777f753..4c5e0e9139458 100644
--- a/library/std/src/thread/local.rs
+++ b/library/std/src/thread/local.rs
@@ -166,7 +166,10 @@ impl<T: 'static> fmt::Debug for LocalKey<T> {
 /// ```
 /// use std::cell::Cell;
 /// thread_local! {
-///     pub static FOO: Cell<u32> = const { Cell::new(1) };
+///     pub static FOO: Cell<u32> = const {
+///         let value = 1;
+///         Cell::new(value)
+///     };
 /// }
 ///
 /// assert_eq!(FOO.get(), 1);
@@ -186,12 +189,12 @@ macro_rules! thread_local {
     // empty (base case for the recursion)
     () => {};
 
-    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = const { $init:expr }; $($rest:tt)*) => (
+    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = const $init:block; $($rest:tt)*) => (
         $crate::thread::local_impl::thread_local_inner!($(#[$attr])* $vis $name, $t, const $init);
         $crate::thread_local!($($rest)*);
     );
 
-    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = const { $init:expr }) => (
+    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = const $init:block) => (
         $crate::thread::local_impl::thread_local_inner!($(#[$attr])* $vis $name, $t, const $init);
     );
 

From f52b88e91f2d185a8be2bf4243827f7b720cd513 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 20 Jan 2024 18:39:48 -0800
Subject: [PATCH 2/3] Revert example change from PR 116392

---
 library/std/src/thread/local.rs | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/library/std/src/thread/local.rs b/library/std/src/thread/local.rs
index 4c5e0e9139458..2e13f433dcffb 100644
--- a/library/std/src/thread/local.rs
+++ b/library/std/src/thread/local.rs
@@ -166,10 +166,7 @@ impl<T: 'static> fmt::Debug for LocalKey<T> {
 /// ```
 /// use std::cell::Cell;
 /// thread_local! {
-///     pub static FOO: Cell<u32> = const {
-///         let value = 1;
-///         Cell::new(value)
-///     };
+///     pub static FOO: Cell<u32> = const { Cell::new(1) };
 /// }
 ///
 /// assert_eq!(FOO.get(), 1);

From c43344e839906624a388847906f6a9b27dcd35c4 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 20 Jan 2024 18:48:41 -0800
Subject: [PATCH 3/3] Add test of thread_local containing multiline const block

Before making thread_local accept statements inside the const block,
this test would fail to compile as follows:

    error: no rules expected the token `let`
       --> library/std/tests/thread.rs:26:13
        |
    26  |             let value = 1;
        |             ^^^ no rules expected this token in macro call
        |
    note: while trying to match meta-variable `$init:expr`
       --> library/std/src/thread/local.rs:189:69
        |
    189 |     ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = const { $init:expr }; $($rest:tt)*) => (
        |                                                                     ^^^^^^^^^^
---
 library/std/tests/thread.rs | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/library/std/tests/thread.rs b/library/std/tests/thread.rs
index 754b264c6ad93..4ce81f2846ea9 100644
--- a/library/std/tests/thread.rs
+++ b/library/std/tests/thread.rs
@@ -1,3 +1,4 @@
+use std::cell::{Cell, RefCell};
 use std::sync::{Arc, Mutex};
 use std::thread;
 use std::time::Duration;
@@ -14,3 +15,24 @@ fn sleep() {
     thread::sleep(Duration::from_millis(100));
     assert_eq!(*finished.lock().unwrap(), false);
 }
+
+#[test]
+fn thread_local_containing_const_statements() {
+    // This exercises the `const $init:block` cases of the thread_local macro.
+    // Despite overlapping with expression syntax, the `const { ... }` is not
+    // parsed as `$init:expr`.
+    thread_local! {
+        static CELL: Cell<u32> = const {
+            let value = 1;
+            Cell::new(value)
+        };
+
+        static REFCELL: RefCell<u32> = const {
+            let value = 1;
+            RefCell::new(value)
+        };
+    }
+
+    assert_eq!(CELL.get(), 1);
+    assert_eq!(REFCELL.take(), 1);
+}