[StdLib][RFC][DNM] Add isIdentical Methods for Quick Comparisons to Array, ArraySlice, and ContiguousArray

stdlib/public/core/Array.swift

@@ -2136,3 +2136,33 @@ internal struct _ArrayAnyHashableBox<Element: Hashable>
 }
 
 extension Array: @unchecked Sendable where Element: Sendable { }
+
+extension Array {
+  /// Returns a boolean value indicating whether this array is identical to
+  /// `other`.
+  ///
+  /// Two array values are identical if there is no way to distinguish between
+  /// them.
+  ///
+  /// Comparing arrays this way includes comparing (normally) hidden
+  /// implementation details such as the memory location of any underlying
+  /// array storage object. Therefore, identical arrays are guaranteed to
+  /// compare equal with `==`, but not all equal arrays are considered
+  /// identical.
+  ///
+  /// - Performance: O(1)
+  @_alwaysEmitIntoClient
+  public func isIdentical(to other: Self) -> Bool {
+    let lhsCount = self.count
+    if lhsCount != other.count {
+      return false
+    }
+
+    // Test referential equality.
+    if unsafe lhsCount == 0 || self._buffer.identity == other._buffer.identity {
+      return true
+    }
+
+    return false
+  }
+}

stdlib/public/core/ArraySlice.swift

@@ -1586,3 +1586,33 @@ extension ArraySlice {
   }
 }
 #endif
+
+extension ArraySlice {
+  /// Returns a boolean value indicating whether this array is identical to
+  /// `other`.
+  ///
+  /// Two array values are identical if there is no way to distinguish between
+  /// them.
+  ///
+  /// Comparing arrays this way includes comparing (normally) hidden
+  /// implementation details such as the memory location of any underlying
+  /// array storage object. Therefore, identical arrays are guaranteed to
+  /// compare equal with `==`, but not all equal arrays are considered
+  /// identical.
+  ///
+  /// - Performance: O(1)
+  @_alwaysEmitIntoClient
+  public func isIdentical(to other: Self) -> Bool {
+    let lhsCount = self.count
+    if lhsCount != other.count {
+      return false
+    }
+
+    // Test referential equality.
+    if unsafe lhsCount == 0 || self._buffer.identity == other._buffer.identity {
+      return true
+    }
+
+    return false
+  }
+}

stdlib/public/core/ContiguousArray.swift

@@ -1495,3 +1495,33 @@ extension ContiguousArray {
 
 extension ContiguousArray: @unchecked Sendable
   where Element: Sendable { }
+
+extension ContiguousArray {
+  /// Returns a boolean value indicating whether this array is identical to
+  /// `other`.
+  ///
+  /// Two array values are identical if there is no way to distinguish between
+  /// them.
+  ///
+  /// Comparing arrays this way includes comparing (normally) hidden
+  /// implementation details such as the memory location of any underlying
+  /// array storage object. Therefore, identical arrays are guaranteed to
+  /// compare equal with `==`, but not all equal arrays are considered
+  /// identical.
+  ///
+  /// - Performance: O(1)
+  @_alwaysEmitIntoClient
+  public func isIdentical(to other: Self) -> Bool {
+    let lhsCount = self.count
+    if lhsCount != other.count {
+      return false
+    }
+
+    // Test referential equality.
+    if unsafe lhsCount == 0 || self._buffer.identity == other._buffer.identity {
+      return true
+    }
+
+    return false
+  }
+}