Add field layout tests

src/TypeSystem/src/Common/FieldLayout.cs

@@ -546,10 +546,13 @@ internal void ComputeInstanceFieldLayout()
             _instanceFieldAlignment = computedLayout.FieldAlignment;
             _instanceByteCount = computedLayout.ByteCount;
 
-            foreach (var fieldAndOffset in computedLayout.Offsets)
+            if (computedLayout.Offsets != null)
             {
-                Debug.Assert(fieldAndOffset.Field.OwningType == this);
-                fieldAndOffset.Field.InitializeOffset(fieldAndOffset.Offset);
+                foreach (var fieldAndOffset in computedLayout.Offsets)
+                {
+                    Debug.Assert(fieldAndOffset.Field.OwningType == this);
+                    fieldAndOffset.Field.InitializeOffset(fieldAndOffset.Offset);
+                }
             }
 
             _fieldLayoutFlags.AddFlags(FieldLayoutFlags.HasInstanceFieldLayout);

src/TypeSystem/tests/CoreTestAssembly/CoreTestAssembly.csproj

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.props))\dir.props" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <OutputType>Library</OutputType>
+    <AssemblyName>CoreTestAssembly</AssemblyName>
+
+    <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
+    <IsCoreAssembly>true</IsCoreAssembly>
+
+    <!--
+      Need to avoid target platform being empty because that would drag in an mscorlib design-time
+      facade into the references and break us.
+    -->
+    <TargetPlatformIdentifier>Portable</TargetPlatformIdentifier>
+    <TargetFrameworkIdentifier>.NETPortable</TargetFrameworkIdentifier>
+    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
+    <TargetFrameworkProfile>Profile7</TargetFrameworkProfile>
+    <TargetFrameworkMonikerDisplayName>.NET Portable Subset</TargetFrameworkMonikerDisplayName>
+    <ImplicitlyExpandTargetFramework>false</ImplicitlyExpandTargetFramework>
+
+  </PropertyGroup>
+
+  <!-- Default configurations to help VS understand the configurations -->
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Platform.cs" />
+    <Compile Include="InstanceFieldLayout.cs" />
+  </ItemGroup>
+
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
+</Project>

src/TypeSystem/tests/CoreTestAssembly/InstanceFieldLayout.cs

@@ -0,0 +1,132 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Runtime.InteropServices;
+
+#pragma warning disable 169
+
+namespace ContainsPointers
+{
+    struct NoPointers
+    {
+        int int1;
+        byte byte1;
+        char char1;
+    }
+
+    struct StillNoPointers
+    {
+        NoPointers noPointers1;
+        bool bool1;
+    }
+
+    class ClassNoPointers
+    {
+        char char1;
+    }
+
+    struct HasPointers
+    {
+        string string1;
+    }
+
+    struct FieldHasPointers
+    {
+        HasPointers hasPointers1;
+    }
+
+    class ClassHasPointers
+    {
+        ClassHasPointers classHasPointers1;
+    }
+
+    class BaseClassHasPointers : ClassHasPointers
+    {
+    }
+
+    public class ClassHasIntArray
+    {
+        int[] intArrayField;
+    }
+
+    public class ClassHasArrayOfClassType
+    {
+        ClassNoPointers[] classTypeArray;
+    }
+}
+
+namespace Explicit
+{
+    [StructLayout(LayoutKind.Explicit)]
+    class Class1
+    {
+        static int Stat;
+        [FieldOffset(4)]
+        bool Bar;
+        [FieldOffset(10)]
+        char Baz;
+    }
+
+    [StructLayout(LayoutKind.Explicit)]
+    class Class2 : Class1
+    {
+        [FieldOffset(0)]
+        int Lol;
+        [FieldOffset(20)]
+        byte Omg;
+    }
+
+    [StructLayout(LayoutKind.Explicit, Size = 40)]
+    class ExplicitSize : Class1
+    {
+        [FieldOffset(0)]
+        int Lol;
+        [FieldOffset(20)]
+        byte Omg;
+    }
+
+    [StructLayout(LayoutKind.Explicit)]
+    public class ExplicitEmptyClass
+    {
+    }
+
+    [StructLayout(LayoutKind.Explicit)]
+    public struct ExplicitEmptyStruct
+    {
+    }
+}
+
+namespace Sequential
+{
+    class Class1
+    {
+        int MyInt;
+        bool MyBool;
+        char MyChar;
+        string MyString;
+        byte[] MyByteArray;
+        Class1 MyClass1SelfRef;
+    }
+
+    class Class2 : Class1
+    {
+        int MyInt2;
+    }
+
+    struct Struct0
+    {
+        bool b1;
+        bool b2;
+        bool b3;
+        int i1;
+        string s1;
+    }
+
+    struct Struct1
+    {
+        Struct0 MyStruct0;
+        bool MyBool;
+    }
+}
+

src/TypeSystem/tests/CoreTestAssembly/Platform.cs

@@ -0,0 +1,83 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+#pragma warning disable 649
+
+namespace System
+{
+    // Dummy core types to allow us compiling this assembly as a core library so that the type
+    // system tests don't have a dependency on a real core library.
+
+    // We might need to bring in some extra things (Interface lists? Virtual methods on Object?),
+    // but let's postpone that until actually needed.
+
+    public class Object
+    {
+        internal IntPtr m_pEEType;
+    }
+
+    public struct Void { }
+    public struct Boolean { }
+    public struct Char { }
+    public struct SByte { }
+    public struct Byte { }
+    public struct Int16 { }
+    public struct UInt16 { }
+    public struct Int32 { }
+    public struct UInt32 { }
+    public struct Int64 { }
+    public struct UInt64 { }
+    public struct IntPtr { }
+    public struct UIntPtr { }
+    public struct Single { }
+    public struct Double { }
+    public abstract class ValueType { }
+    public abstract class Enum : ValueType { }
+    public struct Nullable<T> where T : struct { }
+
+    public sealed class String { }
+    public abstract class Array { }
+    public abstract class Delegate { }
+    public abstract class MulticastDelegate : Delegate { }
+
+    public struct RuntimeTypeHandle { }
+    public struct RuntimeMethodHandle { }
+    public struct RuntimeFieldHandle { }
+
+    public class Attribute { }
+}
+
+namespace System.Runtime.InteropServices
+{
+    public enum LayoutKind
+    {
+        Sequential = 0, // 0x00000008,
+        Explicit = 2, // 0x00000010,
+        Auto = 3, // 0x00000000,
+    }
+
+    public sealed class StructLayoutAttribute : Attribute
+    {
+        internal LayoutKind _val;
+
+        public StructLayoutAttribute(LayoutKind layoutKind)
+        {
+            _val = layoutKind;
+        }
+
+        public LayoutKind Value { get { return _val; } }
+        public int Pack;
+        public int Size;
+    }
+
+    public sealed class FieldOffsetAttribute : Attribute
+    {
+        private int _val;
+        public FieldOffsetAttribute(int offset)
+        {
+            _val = offset;
+        }
+        public int Value { get { return _val; } }
+    }
+}
+