Add tests for dependency graph (#4285)

This adds a unit test for `ILCompiler.Compiler` so that we can no longer
use this as an excuse not to write unit tests for this assembly.

The first test is a generalized framework to write tests for dependency
graph. The test runs ILScanner on a method from the test assembly, and
validates various invariants that the method declares. This will let us
e.g. write targeted unit tests that check that the various size on disk
features within the compiler do the right thing (e.g. make sure we don't
unnecessarily expand variant interfaces, GVMs, etc.).

3 files changed, 4 insertions, 4 deletions

diff --git a/src/Runtime.Base/src/System/Runtime/InteropServices/CallingConvention.cs b/src/Runtime.Base/src/System/Runtime/InteropServices/CallingConvention.cs
index a03b8a950..3b18fdee3 100644
--- a/src/Runtime.Base/src/System/Runtime/InteropServices/CallingConvention.cs
+++ b/src/Runtime.Base/src/System/Runtime/InteropServices/CallingConvention.cs
@@ -5,7 +5,7 @@
 namespace System.Runtime.InteropServices
 {
     // Used for the CallingConvention named argument to the DllImport and NativeCallable attribute
-    internal enum CallingConvention
+    public enum CallingConvention
     {
         Winapi = 1,
         Cdecl = 2,
diff --git a/src/Runtime.Base/src/System/Runtime/InteropServices/DllImportAttribute.cs b/src/Runtime.Base/src/System/Runtime/InteropServices/DllImportAttribute.cs
index 8ebc5fbe3..53a6fea04 100644
--- a/src/Runtime.Base/src/System/Runtime/InteropServices/DllImportAttribute.cs
+++ b/src/Runtime.Base/src/System/Runtime/InteropServices/DllImportAttribute.cs
@@ -5,7 +5,7 @@
 namespace System.Runtime.InteropServices
 {
     [AttributeUsage(AttributeTargets.Method)]
-    internal sealed class DllImportAttribute : Attribute
+    public sealed class DllImportAttribute : Attribute
     {
         public CallingConvention CallingConvention;
 
diff --git a/src/Runtime.Base/src/System/RuntimeTypeHandle.cs b/src/Runtime.Base/src/System/RuntimeTypeHandle.cs
index 19654f883..018057b33 100644
--- a/src/Runtime.Base/src/System/RuntimeTypeHandle.cs
+++ b/src/Runtime.Base/src/System/RuntimeTypeHandle.cs
@@ -11,13 +11,13 @@ using System.Runtime.InteropServices;
 
 namespace System
 {
-    internal class Type
+    public class Type
     {
         public RuntimeTypeHandle TypeHandle { get { return default(RuntimeTypeHandle); } }
     }
 
     [StructLayout(LayoutKind.Sequential)]
-    internal struct RuntimeTypeHandle
+    public struct RuntimeTypeHandle
     {
         private EETypePtr _pEEType;