Code inspection: Redundant 'notnull' constraint on type parameter constrained by non-nullable base type

This inspection reports a notnull constraint when another constraint already guarantees that the type parameter cannot be nullable. In that case, the extra notnull does not strengthen the contract.

Example

                #nullable enable
                using System;

                class C
                {
                    void M<T>() where T : notnull, IDisposable
                    {
                    }
                }
            

                #nullable enable
                using System;

                class C
                {
                    void M<T>() where T : IDisposable
                    {
                    }
                }
            

Quick-fix

The quick-fix removes the redundant notnull constraint. This usually happens when a non-nullable base type constraint already makes the type parameter non-nullable.

13 April 2026