Code Analysis Error: "does not override 'Object.Equals(object o)' and 'Object.GetHashCode()'"

Hi. I'm using version the CommandLine tools, version 2017.1.20170407.131846

My class definition is

--------

    public sealed class ChangeId
    {
        public override bool Equals(object obj)
        {
        }

        public override int GetHashCode()
        {
        }

        public static bool operator ==(ChangeId changeId1, ChangeId changeId2)
        {
        }

        public static bool operator !=(ChangeId changeId1, ChangeId changeId2)
        {
        }
    }

--------

However, analysis using the CommandLine Tools throws the error:

warning CSharpWarnings: :CS0660,CS0661: 'ChangeId' defines operator '==' or operator '!=' but does not override 'Object.Equals(object o)' and 'Object.GetHashCode()'

What am I doing wrong?

Thank you for your time