From 9bf4c712ad7989d6a91dbe68748b8829a50837e4 Mon Sep 17 00:00:00 2001
From: George Barnett <gbarnett@apple.com>
Date: Wed, 24 Jul 2024 20:31:27 +0100
Subject: [PATCH] Change 'unsafeDowncast' to 'as!' (#52)

Motivation:

The 'unsafeDowncast' can cause a miscompile leading to unexpected
runtime behaviour.

Modifications:

- Use 'as!' instead

Result:

No miscompiles on 5.10
---
 Sources/OpenAPIURLSession/BufferedStream/Lock.swift | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Sources/OpenAPIURLSession/BufferedStream/Lock.swift b/Sources/OpenAPIURLSession/BufferedStream/Lock.swift
index db78c8b..b6e82e2 100644
--- a/Sources/OpenAPIURLSession/BufferedStream/Lock.swift
+++ b/Sources/OpenAPIURLSession/BufferedStream/Lock.swift
@@ -111,7 +111,8 @@ final class LockStorage<Value>: ManagedBuffer<Value, LockPrimitive> {
     let buffer = Self.create(minimumCapacity: 1) { _ in
       return value
     }
-    let storage = unsafeDowncast(buffer, to: Self.self)
+    // Avoid 'unsafeDowncast' as there is a miscompilation on 5.10.
+    let storage = buffer as! Self
 
     storage.withUnsafeMutablePointers { _, lockPtr in
       LockOperations.create(lockPtr)