From f63faee85e4249baaff7c40e1a287abb5c6dbdd0 Mon Sep 17 00:00:00 2001
From: Gary Guo <gary@garyguo.net>
Date: Fri, 27 Sep 2024 23:51:03 +0100
Subject: [PATCH] read: use const generics in `src/read/util.rs`

The MSRV has been bumped past the minimum required for const generics.
---
 src/read/util.rs | 80 +++++++++++++++++++-----------------------------
 1 file changed, 31 insertions(+), 49 deletions(-)

diff --git a/src/read/util.rs b/src/read/util.rs
index 041ca5af..39adab32 100644
--- a/src/read/util.rs
+++ b/src/read/util.rs
@@ -41,70 +41,52 @@ pub trait ArrayLike: Sealed {
     fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<Self::Item>];
 }
 
-// Use macro since const generics can't be used due to MSRV.
-macro_rules! impl_array {
-    () => {};
-    ($n:literal $($rest:tt)*) => {
-        // SAFETY: does not modify the content in storage.
-        unsafe impl<T> Sealed for [T; $n] {
-            type Storage = [MaybeUninit<T>; $n];
-
-            fn new_storage() -> Self::Storage {
-                // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
-                unsafe { MaybeUninit::uninit().assume_init() }
-            }
-        }
+// SAFETY: does not modify the content in storage.
+unsafe impl<T, const N: usize> Sealed for [T; N] {
+    type Storage = [MaybeUninit<T>; N];
 
-        impl<T> ArrayLike for [T; $n] {
-            type Item = T;
+    fn new_storage() -> Self::Storage {
+        // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
+        unsafe { MaybeUninit::uninit().assume_init() }
+    }
+}
 
-            fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
-                storage
-            }
+impl<T, const N: usize> ArrayLike for [T; N] {
+    type Item = T;
 
-            fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
-                storage
-            }
-        }
+    fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
+        storage
+    }
 
-        impl_array!($($rest)*);
+    fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
+        storage
     }
 }
 
+// SAFETY: does not modify the content in storage.
 #[cfg(feature = "read")]
-macro_rules! impl_box {
-    () => {};
-    ($n:literal $($rest:tt)*) => {
-        // SAFETY: does not modify the content in storage.
-        unsafe impl<T> Sealed for Box<[T; $n]> {
-            type Storage = Box<[MaybeUninit<T>; $n]>;
-
-            fn new_storage() -> Self::Storage {
-                // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
-                Box::new(unsafe { MaybeUninit::uninit().assume_init() })
-            }
-        }
+unsafe impl<T, const N: usize> Sealed for Box<[T; N]> {
+    type Storage = Box<[MaybeUninit<T>; N]>;
 
-        impl<T> ArrayLike for Box<[T; $n]> {
-            type Item = T;
+    fn new_storage() -> Self::Storage {
+        // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
+        Box::new(unsafe { MaybeUninit::uninit().assume_init() })
+    }
+}
 
-            fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
-                &storage[..]
-            }
+#[cfg(feature = "read")]
+impl<T, const N: usize> ArrayLike for Box<[T; N]> {
+    type Item = T;
 
-            fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
-                &mut storage[..]
-            }
-        }
+    fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
+        &storage[..]
+    }
 
-        impl_box!($($rest)*);
+    fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
+        &mut storage[..]
     }
 }
 
-impl_array!(0 1 2 3 4 8 16 32 64 128 192);
-#[cfg(feature = "read")]
-impl_box!(0 1 2 3 4 8 16 32 64 128 192);
-
 #[cfg(feature = "read")]
 unsafe impl<T> Sealed for Vec<T> {
     type Storage = Box<[MaybeUninit<T>]>;