Assign collections we can't handle

docs/Flattening.md

@@ -145,11 +145,11 @@ destination.Name.ShouldBe("name");
 destination.Description.ShouldBe("description");
 destination.Title.ShouldBe("title");
 ```
-So this allows you to reuse the configuration in the existing maps for the child types `InnerSource` and `OtherInnerSource` when mapping the parent types `Source` and `Destination`. It works in a similar way to [mapping inheritance](Mapping-inheritance.html), but it uses composition, not inheritance.
+So this allows you to reuse the configuration in the existing map for the child types `InnerSource` and `OtherInnerSource` when mapping the parent types `Source` and `Destination`. It works in a similar way to [mapping inheritance](Mapping-inheritance.html), but it uses composition, not inheritance.
 
 The order of the parameters in the `IncludeMembers` call is relevant. When mapping a destination member, the first match wins, starting with the source object itself and then with the included child objects in the order you specified. So in the example above, `Name` is mapped from the source object itself and `Description` from `InnerSource` because it's the first match.
 
-Note that this matching is static, it happens at configuration time, not at `Map` time, and the runtime types of the child objects are not considered.
+Note that this matching is static, it happens at configuration time, not at `Map` time, so the runtime types of the child objects are not considered.
 
 IncludeMembers integrates with `ReverseMap`. An included member will be reversed to 
 ```c#

src/AutoMapper/Configuration/ConfigurationValidator.cs

@@ -131,7 +131,10 @@ private void DryRunTypeMap(ICollection<TypeMap> typeMapsChecked, TypePair types,
                 if(mapperToUse is IObjectMapperInfo mapperInfo)
                 {
                     var newTypePair = mapperInfo.GetAssociatedTypes(types);
-                    DryRunTypeMap(typeMapsChecked, newTypePair, null, memberMap);
+                    if (newTypePair != types)
+                    {
+                        DryRunTypeMap(typeMapsChecked, newTypePair, null, memberMap);
+                    }
                 }
             }
         }

src/AutoMapper/Configuration/MapperConfiguration.cs

@@ -300,25 +300,15 @@ private TypeMap GetTypeMap(TypePair initialTypes)
         static List<Type> GetTypeInheritance(Type type)
         {
             var interfaces = type.GetInterfaces();
-            var lastIndex = interfaces.Length - 1;
             var types = new List<Type>(interfaces.Length + 2) { type };
             Type baseType = type;
             while ((baseType = baseType.BaseType) != null)
             {
                 types.Add(baseType);
-                foreach (var interfaceType in baseType.GetInterfaces())
-                {
-                    var interfaceIndex = Array.LastIndexOf(interfaces, interfaceType);
-                    if (interfaceIndex != lastIndex)
-                    {
-                        interfaces[interfaceIndex] = interfaces[lastIndex];
-                        interfaces[lastIndex] = interfaceType;
-                    }
-                }
             }
-            foreach (var interfaceType in interfaces)
+            for(int index = interfaces.Length - 1; index >= 0; index--)
             {
-                types.Add(interfaceType);
+                types.Add(interfaces[index]);
             }
             return types;
         }

src/AutoMapper/Internal/TypeExtensions.cs

@@ -77,8 +77,10 @@ public static Type GetGenericInterface(this Type type, Type genericInterface)
             {
                 return type;
             }
-            foreach (var interfaceType in type.GetInterfaces())
+            var interfaces = type.GetInterfaces();
+            for(int index = interfaces.Length - 1; index >= 0; index--)
             {
+                var interfaceType = interfaces[index];
                 if (interfaceType.IsGenericType(genericInterface))
                 {
                     return interfaceType;

src/AutoMapper/Mappers/CollectionMapper.cs

@@ -47,13 +47,22 @@ Expression MapReadOnlyCollection(Type genericCollectionType, Type genericReadOnl
             Expression MapCollectionCore(Expression destExpression)
             {
                 var destinationType = destExpression.Type;
-                MethodInfo addMethod;
-                bool isIList, mustUseDestination = memberMap is { MustUseDestination: true };
-                Type destinationCollectionType, destinationElementType;
+                var sourceType = sourceExpression.Type;
+                MethodInfo addMethod = null;
+                bool isIList = false, mustUseDestination = memberMap is { MustUseDestination: true };
+                Type destinationCollectionType = null, destinationElementType = null;
                 GetDestinationType();
                 var passedDestination = Variable(destExpression.Type, "passedDestination");
                 var newExpression = Variable(passedDestination.Type, "collectionDestination");
-                var sourceElementType = sourceExpression.Type.GetICollectionType()?.GenericTypeArguments[0] ?? GetEnumerableElementType(sourceExpression.Type);
+                var sourceElementType = GetEnumerableElementType(sourceType);
+                if (destinationCollectionType == null || (sourceType == sourceElementType && destinationType == destinationElementType))
+                {
+                    if (destinationType.IsAssignableFrom(sourceType))
+                    {
+                        return sourceExpression;
+                    }
+                    throw new NotSupportedException($"Unknown collection. Consider a custom type converter from {sourceType} to {destinationType}.");
+                }
                 var itemParam = Parameter(sourceElementType, "item");
                 var itemExpr = configurationProvider.MapExpression(profileMap, new TypePair(sourceElementType, destinationElementType), itemParam);
                 Expression destination, assignNewExpression;
@@ -78,25 +87,36 @@ Expression MapCollectionCore(Expression destExpression)
                 return CheckContext();
                 void GetDestinationType()
                 {
+                    var immutableCollection = !mustUseDestination && destinationType.IsValueType;
+                    if (immutableCollection)
+                    {
+                        return;
+                    }
                     destinationCollectionType = destinationType.GetICollectionType();
-                    destinationElementType = destinationCollectionType?.GenericTypeArguments[0] ?? GetEnumerableElementType(destinationType);
                     isIList = destExpression.Type.IsListType();
                     if (destinationCollectionType == null)
                     {
                         if (isIList)
                         {
                             destinationCollectionType = typeof(IList);
                             addMethod = IListAdd;
+                            destinationElementType = GetEnumerableElementType(destinationType);
                         }
                         else
                         {
+                            if (!destinationType.IsInterface)
+                            {
+                                return;
+                            }
+                            destinationElementType = GetEnumerableElementType(destinationType);
                             destinationCollectionType = typeof(ICollection<>).MakeGenericType(destinationElementType);
                             destExpression = Convert(mustUseDestination ? destExpression : Null, destinationCollectionType);
                             addMethod = destinationCollectionType.GetMethod("Add");
                         }
                     }
                     else
                     {
+                        destinationElementType = destinationCollectionType.GenericTypeArguments[0];
                         addMethod = destinationCollectionType.GetMethod("Add");
                     }
                 }

src/AutoMapper/QueryableExtensions/ProjectionBuilder.cs

@@ -106,7 +106,7 @@ bool OverMaxDepth()
             }
             void ProjectProperties()
             {
-                foreach (var propertyMap in typeMap.PropertyMaps.Where(pm => pm.CanResolveValue && pm.DestinationMember.CanBeSet()).OrderBy(pm => pm.DestinationName))
+                foreach (var propertyMap in typeMap.PropertyMaps.Where(pm => pm.CanResolveValue && pm.DestinationMember.CanBeSet()).OrderBy(pm => pm.DestinationMember.MetadataToken))
                 {
                     var propertyProjection = TryProjectMember(propertyMap, propertyMap.ExplicitExpansion);
                     if (propertyProjection != null)

src/UnitTests/CollectionMapping.cs

@@ -6,11 +6,61 @@
 using Xunit;
 using Shouldly;
 using System.Collections;
-using System.Reflection;
 using AutoMapper.Internal;
+using System.Collections.Immutable;
 
 namespace AutoMapper.UnitTests
 {
+    public class ImmutableCollection : AutoMapperSpecBase
+    {
+        class Source
+        {
+            public string Value { get; set; }
+        }
+        class Destination
+        {
+            public ImmutableArray<int> Value { get; set; }
+        }
+        protected override MapperConfiguration CreateConfiguration() => new(c => 
+            c.CreateMap<Source, Destination>().ForMember(d=>d.Value, o=>o.MapFrom(_=>ImmutableArray.Create<int>())));
+        [Fact]
+        public void Should_work() => Map<Destination>(new Source()).Value.ShouldBeOfType<ImmutableArray<int>>();
+    }
+    public class AssignableCollection : AutoMapperSpecBase
+    {
+        class Source
+        {
+            public string Value { get; set; }
+        }
+        class Destination
+        {
+            public MyJObject Value { get; set; }
+        }
+        class MyJObject : IEnumerable
+        {
+            public IEnumerator GetEnumerator() => throw new NotImplementedException();
+        }
+        protected override MapperConfiguration CreateConfiguration() => new(c => 
+            c.CreateMap<Source, Destination>().ForMember(d=>d.Value, o=>o.MapFrom(_=>new MyJObject())));
+        [Fact]
+        public void Should_work() => Map<Destination>(new Source()).Value.ShouldBeOfType<MyJObject>();
+    }
+    public class RecursiveCollection : AutoMapperSpecBase
+    {
+        class Source
+        {
+            public string Value { get; set; }
+        }
+        class Destination
+        {
+            public MyJObject Value { get; set; }
+        }
+        class MyJObject : List<MyJObject>{}
+        protected override MapperConfiguration CreateConfiguration() => new(c => 
+            c.CreateMap<Source, Destination>().ForMember(d=>d.Value, o=>o.MapFrom(_=>new MyJObject())));
+        [Fact]
+        public void Should_work() => Map<Destination>(new Source()).Value.ShouldBeOfType<MyJObject>();
+    }
     public class AmbigousMethod : AutoMapperSpecBase
     {
         public class Source