From 8d52279b9809ef27eabe7d5420f03734528f19da Mon Sep 17 00:00:00 2001
From: Stephen Celis <stephen@stephencelis.com>
Date: Wed, 27 Nov 2024 10:01:59 -0600
Subject: [PATCH] Fix Swift 5.9 (#111)

* Fix Swift 5.9

* Fix
---
 Sources/PerceptionCore/Internal/ThreadLocal.swift          | 7 ++++++-
 .../Internal/{UncheckedSendable.swift => Unchecked.swift}  | 6 ++++++
 2 files changed, 12 insertions(+), 1 deletion(-)
 rename Sources/PerceptionCore/Internal/{UncheckedSendable.swift => Unchecked.swift} (50%)

diff --git a/Sources/PerceptionCore/Internal/ThreadLocal.swift b/Sources/PerceptionCore/Internal/ThreadLocal.swift
index 02a3845..c1af3ca 100644
--- a/Sources/PerceptionCore/Internal/ThreadLocal.swift
+++ b/Sources/PerceptionCore/Internal/ThreadLocal.swift
@@ -13,7 +13,12 @@ import Foundation
 
 struct _ThreadLocal {
   #if os(WASI)
-    static nonisolated(unsafe) var value: UnsafeMutableRawPointer?
+    // NB: This can simply be 'nonisolated(unsafe)' when we drop support for Swift 5.9
+    static var value: UnsafeMutableRawPointer? {
+      get { _value.value }
+      set { _value.value = newValue }
+    }
+    private static let _value = UncheckedBox<UnsafeMutableRawPointer?>(nil)
   #else
     static var value: UnsafeMutableRawPointer? {
       get { Thread.current.threadDictionary[Key()] as! UnsafeMutableRawPointer? }
diff --git a/Sources/PerceptionCore/Internal/UncheckedSendable.swift b/Sources/PerceptionCore/Internal/Unchecked.swift
similarity index 50%
rename from Sources/PerceptionCore/Internal/UncheckedSendable.swift
rename to Sources/PerceptionCore/Internal/Unchecked.swift
index 712c62f..ea7e8e9 100644
--- a/Sources/PerceptionCore/Internal/UncheckedSendable.swift
+++ b/Sources/PerceptionCore/Internal/Unchecked.swift
@@ -1,3 +1,9 @@
+@usableFromInline final class UncheckedBox<Value>: @unchecked Sendable {
+  @usableFromInline var value: Value
+  @usableFromInline init(_ value: Value) {
+    self.value = value
+  }
+}
 @usableFromInline struct UncheckedSendable<Value>: @unchecked Sendable {
   @usableFromInline let value: Value
   @usableFromInline init(_ value: Value) {