Fixed stack overflow when mapping recursive collections

Author: gmarz

Diff for: src/Nest/Resolvers/Writers/TypeMappingWriter.cs

@@ -155,7 +155,7 @@ internal void WriteProperties(JsonWriter jsonWriter)
 					if (type == "object" || type == "nested")
 					{
 
-						var deepType = p.PropertyType;
+						var deepType = GetUnderlyingType(p.PropertyType);
 						var deepTypeName = this.Infer.TypeName(deepType);
 						var seenTypes = new ConcurrentDictionary<Type, int>(this.SeenTypes);
 						seenTypes.AddOrUpdate(deepType, 0, (t, i) => ++i);

Diff for: src/Tests/Nest.Tests.Unit/Core/AttributeBasedMap/DeepObjectMappingTests.cs

@@ -1,4 +1,5 @@
 using NUnit.Framework;
+using System.Collections.Generic;
 
 namespace Nest.Tests.Unit.Core.AttributeBasedMap
 {
@@ -29,6 +30,12 @@ private class NestedRecursiveMapChild
 			public string Name { get; set; }
 			public NestedRecursiveMapParent Parent { get; set; }
 		}
+		private class RecursiveMapCollection
+		{
+			public string Name { get; set; }
+			public IEnumerable<RecursiveMapCollection> Items { get; set; }
+		}
+
 		[Test]
 		public void TestDeepObjectWriter()
 		{ 
@@ -41,5 +48,10 @@ public void TestDeepObjectResursiveWriter()
 			//make sure we dont stackoverflow because of a never ending recursion
 		  Assert.DoesNotThrow(() => this.CreateMapFor<NestedRecursiveMapParent>() );
 		}
+		[Test]
+		public void TestRecursiveCollectionWriter()
+		{
+			Assert.DoesNotThrow(() => this.CreateMapFor<RecursiveMapCollection>());
+		}
 	}
 }