simplify

src/AutoMapper/Configuration/MappingExpressionBase.cs

@@ -457,7 +457,7 @@ public TMappingExpression ConstructUsing(Func<TSource, ResolutionContext, TDesti
         public void ConvertUsing(Type typeConverterType)
         {
             HasTypeConverter = true;
-            TypeMapActions.Add(tm => tm.TypeConverter = new ClassTypeConverter(tm.Types, typeConverterType));
+            TypeMapActions.Add(tm => tm.TypeConverter = new ClassTypeConverter(typeConverterType, tm.Types.ITypeConverter()));
         }
 
         public void ConvertUsing(Func<TSource, TDestination, TDestination> mappingFunction)
@@ -485,7 +485,7 @@ public void ConvertUsing(Func<TSource, TDestination, ResolutionContext, TDestina
         public void ConvertUsing<TTypeConverter>() where TTypeConverter : ITypeConverter<TSource, TDestination>
         {
             HasTypeConverter = true;
-            TypeMapActions.Add(tm => tm.TypeConverter = new ClassTypeConverter(Types, typeof(TTypeConverter), typeof(ITypeConverter<TSource, TDestination>)));
+            TypeMapActions.Add(tm => tm.TypeConverter = new ClassTypeConverter(typeof(TTypeConverter), typeof(ITypeConverter<TSource, TDestination>)));
         }
 
         public TMappingExpression ForCtorParam(string ctorParamName, Action<ICtorParamConfigurationExpression<TSource>> paramOptions)

src/AutoMapper/Execution/TypeMapPlanBuilder.cs

@@ -469,16 +469,11 @@ public class LambdaTypeConverter : TypeConverter
     }
     public class ClassTypeConverter : TypeConverter
     {
-        public ClassTypeConverter(TypePair types, Type converterType, Type converterInterface)
+        public ClassTypeConverter(Type converterType, Type converterInterface)
         {
-            Types = types;
             ConverterType = converterType;
             ConverterInterface = converterInterface;
         }
-        public ClassTypeConverter(TypePair types, Type converterType) : this(types, converterType, types.ContainsGenericParameters ? null : types.ITypeConverter())
-        {
-        }
-        public TypePair Types { get; }
         public Type ConverterType { get; private set; }
         public Type ConverterInterface { get; private set; }
         public override Expression GetExpression(ParameterExpression[] parameters) =>

src/AutoMapper/Internal/TypePair.cs

@@ -53,7 +53,7 @@ public TypePair CloseGenericTypes(TypePair closedTypes)
             var closedDestinationType = DestinationType.IsGenericTypeDefinition ? DestinationType.MakeGenericType(destinationArguments) : DestinationType;
             return new TypePair(closedSourceType, closedDestinationType);
         }
-        public Type ITypeConverter() => typeof(ITypeConverter<,>).MakeGenericType(SourceType, DestinationType);
+        public Type ITypeConverter() => ContainsGenericParameters ? null : typeof(ITypeConverter<,>).MakeGenericType(SourceType, DestinationType);
         public TypePair GetTypeDefinitionIfGeneric() => new TypePair(GetTypeDefinitionIfGeneric(SourceType), GetTypeDefinitionIfGeneric(DestinationType));
         private static Type GetTypeDefinitionIfGeneric(Type type) => type.IsGenericType ? type.GetGenericTypeDefinition() : type;
         public static bool operator ==(TypePair left, TypePair right) => left.Equals(right);