docs: Document CS8080 private accessor override limitation

docs/csharp/language-reference/compiler-messages/property-declaration-errors.md

@@ -234,7 +234,7 @@ These errors enforce the rules for overriding properties in derived classes. For
 - Ensure the member you're overriding is a property, not a field or method (**CS0544**). The `override` keyword on a property can only target a `virtual`, `abstract`, or `override` property in a base class. To shadow a non-property member with a property, use the `new` keyword instead of `override`.
 - Override only the accessors that exist in the base class property declaration (**CS0545**, **CS0546**). You can't override a property accessor that isn't present or accessible in the base class because there's no virtual method to override. If the base class property has only a `get` accessor, you can't add a `set` accessor through an override. Either add the missing accessor to the base class and mark it `virtual`, or use `new` to hide the base class property with a new property definition.
 - Match the type of the overriding property to the type of the overridden member (**CS1715**). Read-only (`get`-only) properties support covariant return types beginning with C# 9, so the override can return a more derived type. However, properties that have a `set` or `init` accessor require an exact type match because the setter accepts values of the declared type. If you need a different type on a property with a setter, change the property type in the derived class to match the base class declaration, or remove the setter and use a covariant return type instead.
-- Include all accessors from the base property when overriding with an auto-implemented property (**CS8080**). Auto-implemented properties generate both storage and accessor implementations, so they must override all accessors present in the base class. If the base property has both `get` and `set`, the auto-implemented override must also have both. To override only specific accessors, implement the property with explicit accessor bodies and an explicit backing field instead of using auto-implementation.
+- Include all accessors from the base property when overriding with an auto-implemented property (**CS8080**). Auto-implemented properties generate both storage and accessor implementations, so they must override all accessors present in the base class. If the base property has both `get` and `set`, the auto-implemented override must also have both. To override only specific accessors, implement the property with explicit accessor bodies and an explicit backing field instead of using auto-implementation. If the base class property has a `private` accessor, you can't override the property with an auto-implemented property—use explicit accessor bodies instead.
 
 For more information, see [Inheritance](../../fundamentals/object-oriented/inheritance.md), [Properties](../../programming-guide/classes-and-structs/properties.md), and [Using Properties](../../programming-guide/classes-and-structs/using-properties.md).