[Fact]
        public void TestErrorsImplementingGenericNestedInterfaces_Explicit()
        {
            var text = @"
using System.Collections.Generic;
class Outer<T>
{
    internal class Inner<U>
    {
        protected internal interface Interface<V, W>
        {
            T Property { set; }
            void Method<Z>(T a, U[] b, List<V> c, Dictionary<W, Z> d);
        }
        internal class Derived4
        {
            internal class Derived5 : Outer<T>.Inner<U>.Interface<U, T>
            {
                T Outer<T>.Inner<U>.Interface<U, T>.Property
                {
                    set { }
                }
                void Inner<U>.Interface<U, T>.Method<K>(T a, U[] b, List<U> c, Dictionary<K, T> D)
                {
                }
            }
            internal class Derived6 : Outer<T>.Inner<U>.Interface<U, T>
            {
                T Outer<T>.Inner<U>.Interface<U, T>.Property
                {
                    set { }
                }
                void Inner<U>.Interface<U, T>.Method<K>(T a, U[] b, List<U> c, Dictionary<T, K> D)
                {
                }
            }
        }
    }
}
";

            // The following error is unexpected:
            // (24,39): error CS0535: 'Outer<T>.Inner<U>.Derived4.Derived6' does not implement interface member 'Outer<T>.Inner<U>.Interface<U, T>.Method<Z>(T, U[], List<U>, Dictionary<T, Z>)'
            CreateCompilation(text, options: WithNonNullTypesTrue()).VerifyDiagnostics(
                // (14,39): error CS0535: 'Outer<T>.Inner<U>.Derived4.Derived5' does not implement interface member 'Outer<T>.Inner<U>.Interface<U, T>.Method<Z>(T, U[], List<U>, Dictionary<T, Z>)'
                //             internal class Derived5 : Outer<T>.Inner<U>.Interface<U, T>
                Diagnostic(ErrorCode.ERR_UnimplementedInterfaceMember, "Outer<T>.Inner<U>.Interface<U, T>").WithArguments("Outer<T>.Inner<U>.Derived4.Derived5", "Outer<T>.Inner<U>.Interface<U, T>.Method<Z>(T, U[], System.Collections.Generic.List<U>, System.Collections.Generic.Dictionary<T, Z>)").WithLocation(14, 39),
                // (20,47): error CS0539: 'Outer<T>.Inner<U>.Derived4.Derived5.Method<K>(T, U[], List<U>, Dictionary<K, T>)' in explicit interface declaration is not a member of interface
                //                 void Inner<U>.Interface<U, T>.Method<K>(T a, U[] b, List<U> c, Dictionary<K, T> D)
                Diagnostic(ErrorCode.ERR_InterfaceMemberNotFound, "Method").WithArguments("Outer<T>.Inner<U>.Derived4.Derived5.Method<K>(T, U[], System.Collections.Generic.List<U>, System.Collections.Generic.Dictionary<K, T>)").WithLocation(20, 47),
                // (24,39): error CS0535: 'Outer<T>.Inner<U>.Derived4.Derived6' does not implement interface member 'Outer<T>.Inner<U>.Interface<U, T>.Method<Z>(T, U[], List<U>, Dictionary<T, Z>)'
                //             internal class Derived6 : Outer<T>.Inner<U>.Interface<U, T>
                Diagnostic(ErrorCode.ERR_UnimplementedInterfaceMember, "Outer<T>.Inner<U>.Interface<U, T>").WithArguments("Outer<T>.Inner<U>.Derived4.Derived6", "Outer<T>.Inner<U>.Interface<U, T>.Method<Z>(T, U[], System.Collections.Generic.List<U>, System.Collections.Generic.Dictionary<T, Z>)").WithLocation(24, 39)
                );
        }

        [Fact]
        public void TestErrorsImplementingGenericNestedInterfaces_Explicit_IncorrectPartialQualification()
        {
            var source = @"
using System.Collections.Generic;
class Outer<T>
{
    internal class Inner<U>
    {
        protected internal interface Interface<V, W>
        {
            T Property { set; }
            void Method<Z>(T a, U[] b, List<V> c, Dictionary<W, Z> d);
        }
        internal class Derived3 : Interface<long, string>
        {
            T Interface<long, string>.Property
            {
                set { }
            }
            void Inner<U>.Interface<long, string>.Method<K>(T a, U[] B, List<long> C, Dictionary<string, K> d)
            {
            }
        }
    }
}
";

            // The following error is unexpected:
            CreateCompilation(source, options: WithNonNullTypesTrue()).VerifyDiagnostics(
                // (12,35): error CS0535: 'Outer<T>.Inner<U>.Derived3' does not implement interface member 'Outer<T>.Inner<U>.Interface<long, string>.Method<Z>(T, U[], List<long>, Dictionary<string, Z>)'
                //         internal class Derived3 : Interface<long, string>
                Diagnostic(ErrorCode.ERR_UnimplementedInterfaceMember, "Interface<long, string>").WithArguments("Outer<T>.Inner<U>.Derived3", "Outer<T>.Inner<U>.Interface<long, string>.Method<Z>(T, U[], System.Collections.Generic.List<long>, System.Collections.Generic.Dictionary<string, Z>)").WithLocation(12, 35)
                );
        }