Code inspection: [NotNull] or [CanBeNull] attribute is applied to a type that already has the same annotation from nullable reference types

This inspection reports nullability attributes such as [NotNull], [CanBeNull], [ItemNotNull], [ItemCanBeNull] when nullable reference type syntax already expresses the same information. Keeping both usually adds noise without improving the contract.

                #nullable enable
                using JetBrains.Annotations;
                class C
                {
                    [NotNull]
                    public string GetName() => "";
                }
            

                #nullable enable
                class C
                {
                    public string GetName() => "";
                }
            

The same applies to collection element annotations when ? on the element type already describes the nullability.

13 April 2026