feat(data_structures): add as_slice + as_mut_slice methods to stacks (#6216)

Add `as_slice` and `as_mut_slice` methods to `Stack` and `NonEmptyStack`.

crates/oxc_data_structures/src/stack/common.rs

@@ -3,7 +3,7 @@
 use std::{
     alloc::{self, Layout},
     mem::{align_of, size_of},
-    ptr,
+    ptr, slice,
 };
 
 use assert_unchecked::assert_unchecked;
@@ -186,6 +186,20 @@ pub trait StackCommon<T>: StackCapacity<T> {
             self.end().byte_offset_from(self.start()) as usize
         }
     }
+
+    /// Get contents of stack as a slice `&[T]`.
+    #[inline]
+    fn as_slice(&self) -> &[T] {
+        // SAFETY: Stack always contains `self.len()` entries, starting at `self.start()`
+        unsafe { slice::from_raw_parts(self.start().as_ptr(), self.len()) }
+    }
+
+    /// Get contents of stack as a mutable slice `&mut [T]`.
+    #[inline]
+    fn as_mut_slice(&mut self) -> &mut [T] {
+        // SAFETY: Stack always contains `self.len()` entries, starting at `self.start()`
+        unsafe { slice::from_raw_parts_mut(self.start().as_ptr(), self.len()) }
+    }
 }
 
 /// Make allocation of with provided layout.

crates/oxc_data_structures/src/stack/non_empty.rs

@@ -1,6 +1,9 @@
 #![expect(clippy::unnecessary_safety_comment)]
 
-use std::mem::size_of;
+use std::{
+    mem::size_of,
+    ops::{Deref, DerefMut},
+};
 
 use super::{NonNull, StackCapacity, StackCommon};
 
@@ -301,6 +304,18 @@ impl<T> NonEmptyStack<T> {
     pub fn capacity(&self) -> usize {
         <Self as StackCommon<T>>::capacity(self)
     }
+
+    /// Get contents of stack as a slice `&[T]`.
+    #[inline]
+    pub fn as_slice(&self) -> &[T] {
+        <Self as StackCommon<T>>::as_slice(self)
+    }
+
+    /// Get contents of stack as a mutable slice `&mut [T]`.
+    #[inline]
+    pub fn as_mut_slice(&mut self) -> &mut [T] {
+        <Self as StackCommon<T>>::as_mut_slice(self)
+    }
 }
 
 impl<T> Drop for NonEmptyStack<T> {
@@ -316,6 +331,22 @@ impl<T> Drop for NonEmptyStack<T> {
     }
 }
 
+impl<T> Deref for NonEmptyStack<T> {
+    type Target = [T];
+
+    #[inline]
+    fn deref(&self) -> &[T] {
+        self.as_slice()
+    }
+}
+
+impl<T> DerefMut for NonEmptyStack<T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut [T] {
+        self.as_mut_slice()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

crates/oxc_data_structures/src/stack/standard.rs

@@ -1,6 +1,9 @@
 #![expect(clippy::unnecessary_safety_comment)]
 
-use std::mem::size_of;
+use std::{
+    mem::size_of,
+    ops::{Deref, DerefMut},
+};
 
 use super::{NonNull, StackCapacity, StackCommon};
 
@@ -324,6 +327,18 @@ impl<T> Stack<T> {
     pub fn capacity(&self) -> usize {
         <Self as StackCommon<T>>::capacity(self)
     }
+
+    /// Get contents of stack as a slice `&[T]`.
+    #[inline]
+    pub fn as_slice(&self) -> &[T] {
+        <Self as StackCommon<T>>::as_slice(self)
+    }
+
+    /// Get contents of stack as a mutable slice `&mut [T]`.
+    #[inline]
+    pub fn as_mut_slice(&mut self) -> &mut [T] {
+        <Self as StackCommon<T>>::as_mut_slice(self)
+    }
 }
 
 impl<T> Drop for Stack<T> {
@@ -345,6 +360,22 @@ impl<T> Drop for Stack<T> {
     }
 }
 
+impl<T> Deref for Stack<T> {
+    type Target = [T];
+
+    #[inline]
+    fn deref(&self) -> &[T] {
+        self.as_slice()
+    }
+}
+
+impl<T> DerefMut for Stack<T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut [T] {
+        self.as_mut_slice()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;