From 265425846f36fd876f828e2d4ae47c6150bcc8b1 Mon Sep 17 00:00:00 2001
From: Alejandro Vaz <alejandro.vaz.myt@gmail.com>
Date: Thu, 24 Sep 2026 15:43:21 +0200
Subject: [PATCH 1/2] refactor: manual location setting

---
 src/lib.rs       | 30 +++++-------------------------
 src/taggedlen.rs |  7 +++++++
 2 files changed, 12 insertions(+), 25 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 5434d44f..4914aad7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -593,26 +593,6 @@ impl<T: Clone, const N: usize> SmallVec<T, N> {
 impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
     const IS_ZST: bool = size_of::<T>() == 0;
 
-    /// Sets the tag to be on the heap
-    ///
-    /// # Safety
-    ///
-    /// The active union member must be the self.raw.heap
-    #[inline]
-    unsafe fn set_on_heap(&mut self) {
-        self.len = TaggedLen::new(self.len(), true);
-    }
-
-    /// Sets the tag to be inline
-    ///
-    /// # Safety
-    ///
-    /// The active union member must be the self.raw.inline
-    #[inline]
-    unsafe fn set_inline(&mut self) {
-        self.len = TaggedLen::new(self.len(), false);
-    }
-
     /// Sets the length of a vector.
     ///
     /// This will explicitly set the size of the vector, without actually
@@ -901,7 +881,7 @@ impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
             if result.is_ok() {
                 // SAFETY: the allocation succeeded, so self.raw.heap is now
                 // active
-                unsafe { self.set_on_heap() };
+                self.len.set_location::<true>();
             }
             result
         } else {
@@ -921,7 +901,7 @@ impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
                         align: align_of::<T>(),
                         alloc: &self.allocator
                     });
-                    self.set_inline();
+                    self.len.set_location::<false>();
                 }
             }
             Ok(())
@@ -993,7 +973,7 @@ impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
             unsafe {
                 let (ptr, capacity) = self.raw.heap;
                 copy_nonoverlapping(ptr.as_ptr(), self.raw.as_mut_ptr_inline(), len);
-                self.set_inline();
+                self.len.set_location::<false>();
                 self.allocator.deallocate(
                     ptr.cast(),
                     Layout::from_size_align_unchecked(capacity * size_of::<T>(), align_of::<T>())
@@ -1026,7 +1006,7 @@ impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
                 unsafe {
                     let (ptr, capacity) = self.raw.heap;
                     copy_nonoverlapping(ptr.as_ptr(), self.raw.as_mut_ptr_inline(), len);
-                    self.set_inline();
+                    self.len.set_location::<false>();
                     self.allocator.deallocate(
                         ptr.cast(),
                         Layout::from_size_align_unchecked(
@@ -1603,7 +1583,7 @@ impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
             }?;
 
             // SAFETY: the allocation succeeded, so self.raw.heap is now active
-            unsafe { this.set_on_heap() };
+            this.len.set_location::<true>();
         }
         Ok(this)
     }
diff --git a/src/taggedlen.rs b/src/taggedlen.rs
index c3571657..5a373c55 100644
--- a/src/taggedlen.rs
+++ b/src/taggedlen.rs
@@ -55,6 +55,13 @@ impl<T> TaggedLen<T> {
         (self.0 >> Self::SHIFT, (self.0 & Self::TAG) != 0)
     }
 
+    #[inline(always)]
+    pub const fn set_location<const ON: bool>(&mut self) {
+        if Self::TAG != 0 {
+            self.0 = (self.0 & !Self::TAG) | ON as usize;
+        }
+    }
+
     /// # Safety
     ///
     /// current len+n must be smaller than MAX_LEN on 64-bit target

From 50557bef95000b4220245c8e032409e5d2b3e53b Mon Sep 17 00:00:00 2001
From: Alejandro Vaz <alejandro.vaz.myt@gmail.com>
Date: Thu, 24 Sep 2026 15:58:58 +0200
Subject: [PATCH 2/2] fix: rename len to length

---
 src/lib.rs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 9e96afad..f45b6a3d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -703,7 +703,7 @@ impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
             if result.is_ok() {
                 // SAFETY: the allocation succeeded, so self.raw.heap is now
                 // active
-                self.len.set_location::<true>();
+                self.length.set_location::<true>();
             }
             result
         } else {
@@ -723,7 +723,7 @@ impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
                         align: align_of::<T>(),
                         allocator: &self.allocator
                     });
-                    self.len.set_location::<false>();
+                    self.length.set_location::<false>();
                 }
             }
             Ok(())
@@ -780,7 +780,7 @@ impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
             unsafe {
                 let (ptr, capacity) = self.raw.heap;
                 copy_nonoverlapping(ptr.as_ptr(), self.raw.as_mut_ptr_inline(), length);
-                self.len.set_location::<false>();
+                self.length.set_location::<false>();
                 self.allocator.deallocate(
                     ptr.cast(),
                     Layout::from_size_align_unchecked(capacity * size_of::<T>(), align_of::<T>())
@@ -813,7 +813,7 @@ impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
                 unsafe {
                     let (ptr, capacity) = self.raw.heap;
                     copy_nonoverlapping(ptr.as_ptr(), self.raw.as_mut_ptr_inline(), length);
-                    self.len.set_location::<false>();
+                    self.length.set_location::<false>();
                     self.allocator.deallocate(
                         ptr.cast(),
                         Layout::from_size_align_unchecked(
@@ -1391,7 +1391,7 @@ impl<T, const N: usize, A: Allocator> SmallVec<T, N, A> {
             }?;
 
             // SAFETY: the allocation succeeded, so self.raw.heap is now active
-            this.len.set_location::<true>();
+            this.length.set_location::<true>();
         }
         Ok(this)
     }