From ac1d494270ac25b3fd885ef7d8b52cb27109861d Mon Sep 17 00:00:00 2001
From: Rodrigo Kumpera <kumpera@gmail.com>
Date: Thu, 28 Sep 2017 13:45:54 -0700
Subject: [PATCH] [runtime] Synthesize IList and IReadOnlyList for the element
 type of enum errays. Fixes #59824

Make sure array of enums can be casted to interfaces of their element types.
---
 mono/metadata/class.c | 24 +++++++++++----
 mono/tests/array.cs   | 70 +++++++++++++++++++++++++------------------
 2 files changed, 60 insertions(+), 34 deletions(-)

diff --git a/mono/metadata/class.c b/mono/metadata/class.c
index e1539de106c..da8fc30585b 100644
--- a/mono/metadata/class.c
+++ b/mono/metadata/class.c
@@ -4955,12 +4955,19 @@ mono_class_init (MonoClass *klass)
 		ghcimpl = cached_info.ghcimpl;
 		has_cctor = cached_info.has_cctor;
 	} else if (klass->rank == 1 && klass->byval_arg.type == MONO_TYPE_SZARRAY) {
-		/* SZARRAY can have 2 vtable layouts, with and without the stelemref method.
+		/* SZARRAY can have 3 vtable layouts, with and without the stelemref method and enum element type
 		 * The first slot if for array with.
 		 */
-		static int szarray_vtable_size[2] = { 0 };
+		static int szarray_vtable_size[3] = { 0 };
 
-		int slot = MONO_TYPE_IS_REFERENCE (&klass->element_class->byval_arg) ? 0 : 1;
+		int slot;
+
+		if (MONO_TYPE_IS_REFERENCE (&klass->element_class->byval_arg))
+			slot = 0;
+		else if (klass->element_class->enumtype)
+			slot = 1;
+		else
+			slot = 2;
 
 		/* SZARRAY case */
 		if (!szarray_vtable_size [slot]) {
@@ -10540,8 +10547,8 @@ mono_class_setup_interfaces (MonoClass *klass, MonoError *error)
 	if (klass->rank == 1 && klass->byval_arg.type != MONO_TYPE_ARRAY) {
 		MonoType *args [1];
 
-		/* generic IList, ICollection, IEnumerable */
-		interface_count = 2;
+		/* IList and IReadOnlyList -> 2x if enum*/
+		interface_count = klass->element_class->enumtype ? 4 : 2;
 		interfaces = (MonoClass **)mono_image_alloc0 (klass->image, sizeof (MonoClass*) * interface_count);
 
 		args [0] = &klass->element_class->byval_arg;
@@ -10549,6 +10556,13 @@ mono_class_setup_interfaces (MonoClass *klass, MonoError *error)
 			mono_defaults.generic_ilist_class, 1, args, FALSE);
 		interfaces [1] = mono_class_bind_generic_parameters (
 			   mono_defaults.generic_ireadonlylist_class, 1, args, FALSE);
+		if (klass->element_class->enumtype) {
+			args [0] = mono_class_enum_basetype (klass->element_class);
+			interfaces [2] = mono_class_bind_generic_parameters (
+				mono_defaults.generic_ilist_class, 1, args, FALSE);
+			interfaces [3] = mono_class_bind_generic_parameters (
+				   mono_defaults.generic_ireadonlylist_class, 1, args, FALSE);
+		}
 	} else if (mono_class_is_ginst (klass)) {
 		MonoClass *gklass = mono_class_get_generic_class (klass)->container_class;
 
diff --git a/mono/tests/array.cs b/mono/tests/array.cs
index b0e9d47ff1e..7b3a68247a8 100644
--- a/mono/tests/array.cs
+++ b/mono/tests/array.cs
@@ -1,14 +1,10 @@
 using System;
+using System.Collections.Generic;
 using System.Runtime.InteropServices;
 
 public class Test {
 
-	static void puts (string s)
-	{
-		Console.WriteLine (s);
-	}
-
-	public static int jagged ()
+	public static int test_0_jagged ()
 	{
 		int[][] j2 = new int [3][];
 
@@ -32,7 +28,7 @@ public class Test {
 		return 0;
 	}
 
-	public static int stest ()
+	public static int test_0_stest ()
 	{
 		string[] sa = new string[32];
 
@@ -44,13 +40,13 @@ public class Test {
 
 		for (int i = 0; i < sa.Length; i++){
 			if (sa [i] != null)
-				puts (sa [i]);
+				Console.WriteLine (sa [i]);
 		}
 		
 		return 0;
 	}
 	
-	public static int atest2 ()
+	public static int test_0_atest2 ()
 	{
 		int[,] ia = new int[32,32];
 
@@ -71,7 +67,7 @@ public class Test {
 		return 0;
 	}
 	
-	public static int atest ()
+	public static int test_0_atest ()
 	{
 		int[] ia = new int[32];
 
@@ -93,35 +89,51 @@ public class Test {
 
 		for (int i = 0; i <ia.Length; i++)
 			if ((int)ia.GetValue (i) != i*i*i){
-				puts ("Crap: " + i + " " + (int) ia.GetValue (i) );
+				Console.WriteLine ("Crap: " + i + " " + (int) ia.GetValue (i) );
 
 				return 4;
 			}
 		
 		return 0;
 	}
-	
 
-	public static int Main () {
-		puts ("a");
-		if (atest () != 0)
-			return atest ();
-	 	puts ("b");	
-		if (atest2 () != 0)
-			return 1;
-		puts ("c");
-		if (atest2 () != 0)
-			return 1;
-		puts ("d");	
-		if (stest () != 0)
+	enum Foo { a, b };
+	public static int test_0_enum_array_casting () {
+        var x = new Foo[10];
+		try {
+			var y = (IReadOnlyList<int>)(object)x;
+		} catch (Exception e) {
 			return 1;
-	 	puts ("e");	
-		if (jagged () != 0)
-			return 1;
-		
-		
+		}
+		try {
+			var y = (IList<int>)(object)x;
+		} catch (Exception e) {
+			return 2;
+		}
+
+		try {
+			var y = (ICollection<int>)(object)x;
+		} catch (Exception e) {
+			return 3;
+		}
+
+		try {
+			var y = (IEnumerable<int>)(object)x;
+		} catch (Exception e) {
+			return 4;
+		}
+
+		try {
+			var y = (IReadOnlyCollection<int>)(object)x;
+		} catch (Exception e) {
+			return 5;
+		}
 		return 0;
 	}
+
+	public static int Main (string[] args) {
+		return TestDriver.RunTests (typeof (Test), args);
+	}
 }
 
 
-- 
2.25.1