From 002df10b8c610788b2730ec1234934e81aaa2880 Mon Sep 17 00:00:00 2001
From: bestgopher <84328409@qq.com>
Date: Tue, 14 Jul 2026 15:45:41 +0800
Subject: [PATCH] Simplify shared alignment assertions (#841)

Replace array-underflow checks with const assert expressions.
Add diagnostics that explain the pointer-tagging alignment invariant.

Signed-off-by: bestgopher <84328409@qq.com>
---
 src/bytes.rs     | 7 ++++++-
 src/bytes_mut.rs | 7 ++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/bytes.rs b/src/bytes.rs
index 0f1aaed..bbd7bdc 100644
--- a/src/bytes.rs
+++ b/src/bytes.rs
@@ -1348,7 +1348,12 @@ impl Drop for Shared {
 // This is a necessary invariant since we depend on allocating `Shared` a
 // shared object to implicitly carry the `KIND_ARC` flag in its pointer.
 // This flag is set when the LSB is 0.
-const _: [(); 0 - mem::align_of::<Shared>() % 2] = []; // Assert that the alignment of `Shared` is divisible by 2.
+const _: () = {
+    assert!(
+        mem::align_of::<Shared>() % 2 == 0,
+        "Shared alignment must be divisible by 2 for pointer tagging"
+    );
+};
 
 static SHARED_VTABLE: Vtable = Vtable {
     clone: shared_clone,
diff --git a/src/bytes_mut.rs b/src/bytes_mut.rs
index b983bd1..ae808fa 100644
--- a/src/bytes_mut.rs
+++ b/src/bytes_mut.rs
@@ -92,7 +92,12 @@ impl Shared {
 // This is a necessary invariant since we depend on allocating `Shared` a
 // shared object to implicitly carry the `KIND_ARC` flag in its pointer.
 // This flag is set when the LSB is 0.
-const _: [(); 0 - mem::align_of::<Shared>() % 2] = []; // Assert that the alignment of `Shared` is divisible by 2.
+const _: () = {
+    assert!(
+        mem::align_of::<Shared>() % 2 == 0,
+        "Shared alignment must be divisible by 2 for pointer tagging"
+    );
+};
 
 // Buffer storage strategy flags.
 const KIND_ARC: usize = 0b0;