add & use NonEmptyStack::first

crates/oxc_data_structures/src/stack/non_empty.rs

@@ -216,6 +216,20 @@ impl<T> NonEmptyStack<T> {
         Self { cursor: start, start, end }
     }
 
+    /// Get reference to first value on stack.
+    #[inline]
+    pub fn first(&self) -> &T {
+        // SAFETY: All methods ensure `self.start` always points to a valid initialized `T`
+        unsafe { self.start.as_ref() }
+    }
+
+    /// Get mutable reference to first value on stack.
+    #[inline]
+    pub fn first_mut(&mut self) -> &mut T {
+        // SAFETY: All methods ensure `self.start` always points to a valid initialized `T`
+        unsafe { self.start.as_mut() }
+    }
+
     /// Get reference to last value on stack.
     #[inline]
     pub fn last(&self) -> &T {

crates/oxc_transformer/src/typescript/enum.rs

@@ -574,9 +574,7 @@ impl IdentifierReferenceRename<'_, '_> {
         //   }
         // }
         // ```
-        //
-        // `NonEmptyStack` guarantees that the stack is not empty.
-        *self.scope_stack.first().unwrap() == symbol_scope_id
+        *self.scope_stack.first() == symbol_scope_id
             // The resolved symbol is declared outside the enum,
             // and we have checked that the name exists in previous_enum_members:
             //