From 6f6e6316be5e8bed85326be5467a8c73c56f14a2 Mon Sep 17 00:00:00 2001
From: Rodrigo Kumpera <kumpera@users.noreply.github.com>
Date: Wed, 21 Feb 2018 14:17:43 -0800
Subject: [PATCH] [runtime] Magic interfaces requires the complex stelemref to
 handle arrays. Fixes gh #6266 (#7038)

Add System.Collections.Generic include to objects.cs
---
 mono/metadata/marshal.c |  5 +++++
 mono/mini/objects.cs    | 25 +++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/mono/metadata/marshal.c b/mono/metadata/marshal.c
index 395c2b5a8474..8333eb5fbd9d 100644
--- a/mono/metadata/marshal.c
+++ b/mono/metadata/marshal.c
@@ -9829,6 +9829,11 @@ get_virtual_stelemref_kind (MonoClass *element_class)
 		return STELEMREF_OBJECT;
 	if (is_monomorphic_array (element_class))
 		return STELEMREF_SEALED_CLASS;
+
+	/* magic ifaces requires aditional checks for when the element type is an array */
+	if (MONO_CLASS_IS_INTERFACE (element_class) && element_class->is_array_special_interface)
+		return STELEMREF_COMPLEX;
+
 	/* Compressed interface bitmaps require code that is quite complex, so don't optimize for it. */
 	if (MONO_CLASS_IS_INTERFACE (element_class) && !mono_class_has_variant_generic_params (element_class))
 #ifdef COMPRESSED_INTERFACE_BITMAP
diff --git a/mono/mini/objects.cs b/mono/mini/objects.cs
index 97ca3c180115..b6e1246fc74a 100644
--- a/mono/mini/objects.cs
+++ b/mono/mini/objects.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Text;
 using System.Reflection;
+using System.Collections.Generic;
 using System.Runtime.InteropServices;
 using System.Runtime.CompilerServices;
 
@@ -1829,6 +1830,30 @@ public static int test_0_typedref () {
 
 		return 0;
 	}
+
+	public interface IFoo
+	{
+	  int MyInt { get; }
+	}
+
+	public class IFooImpl : IFoo
+	{
+	  public int MyInt => 0;
+	}
+
+	//gh 6266
+	public static int test_0_store_to_magic_iface_array ()
+	{
+		ICollection<IFoo> arr1 = new IFooImpl[1] { new IFooImpl() };
+		ICollection<IFoo> arr2 = new IFooImpl[1] { new IFooImpl() };
+
+		ICollection<IFoo>[] a2d = new ICollection<IFoo>[2] {
+			arr1,
+			arr2,
+		};
+
+		return 0;
+	}
 }
 
 #if __MOBILE__