Add function pointer types to the type system (#1920)

Even though these can't be expressed in C#, we still have a bunch of test collateral that exercises them. Instead of coming up with excuses as to why we should just ignore the tests every time it shows up, I decided to just implement this.

Native metadata schema update and emission will follow later.

2 files changed, 39 insertions, 18 deletions

diff --git a/src/ILCompiler.MetadataTransform/src/ILCompiler/Metadata/Transform.Type.cs b/src/ILCompiler.MetadataTransform/src/ILCompiler/Metadata/Transform.Type.cs
index 5c094dc67..4178a4d60 100644
--- a/src/ILCompiler.MetadataTransform/src/ILCompiler/Metadata/Transform.Type.cs
+++ b/src/ILCompiler.MetadataTransform/src/ILCompiler/Metadata/Transform.Type.cs
@@ -53,6 +53,8 @@ namespace ILCompiler.Metadata
                 case Cts.TypeFlags.Pointer:
                     rec = _types.Create((Cts.PointerType)type, _initPointer ?? (_initPointer = InitializePointer));
                     break;
+                case Cts.TypeFlags.FunctionPointer:
+                    throw new NotImplementedException();
                 case Cts.TypeFlags.SignatureTypeVariable:
                     rec = _types.Create((Cts.SignatureTypeVariable)type, _initTypeVar ?? (_initTypeVar = InitializeTypeVariable));
                     break;
diff --git a/src/ILCompiler.MetadataTransform/src/ILCompiler/Metadata/Transform.cs b/src/ILCompiler.MetadataTransform/src/ILCompiler/Metadata/Transform.cs
index a120cd859..3526c2c44 100644
--- a/src/ILCompiler.MetadataTransform/src/ILCompiler/Metadata/Transform.cs
+++ b/src/ILCompiler.MetadataTransform/src/ILCompiler/Metadata/Transform.cs
@@ -2,11 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Collections.Generic;
-using Internal.Metadata.NativeFormat.Writer;
-
 using Cts = Internal.TypeSystem;
+using Debug = System.Diagnostics.Debug;
 
 namespace ILCompiler.Metadata
 {
@@ -28,25 +25,47 @@ namespace ILCompiler.Metadata
 
         private bool IsBlocked(Cts.TypeDesc type)
         {
-            if (type.IsArray || type.IsByRef || type.IsPointer)
-                return IsBlocked(((Cts.ParameterizedType)type).ParameterType);
+            switch (type.Category)
+            {
+                case Cts.TypeFlags.SzArray:
+                case Cts.TypeFlags.Array:
+                case Cts.TypeFlags.Pointer:
+                case Cts.TypeFlags.ByRef:
+                    return IsBlocked(((Cts.ParameterizedType)type).ParameterType);
 
-            if (type.IsSignatureVariable)
-                return false;
+                case Cts.TypeFlags.SignatureMethodVariable:
+                case Cts.TypeFlags.SignatureTypeVariable:
+                    return false;
 
-            if (!type.IsTypeDefinition)
-            {
-                if (IsBlocked(type.GetTypeDefinition()))
-                    return true;
+                case Cts.TypeFlags.FunctionPointer:
+                    {
+                        Cts.MethodSignature pointerSignature = ((Cts.FunctionPointerType)type).Signature;
+                        if (IsBlocked(pointerSignature.ReturnType))
+                            return true;
+
+                        for (int i = 0; i < pointerSignature.Length; i++)
+                            if (IsBlocked(pointerSignature[i]))
+                                return true;
+
+                        return false;
+                    }
+                default:
+                    Debug.Assert(type.IsDefType);
+
+                    if (!type.IsTypeDefinition)
+                    {
+                        if (IsBlocked(type.GetTypeDefinition()))
+                            return true;
 
-                foreach (var arg in type.Instantiation)
-                    if (IsBlocked(arg))
-                        return true;
+                        foreach (var arg in type.Instantiation)
+                            if (IsBlocked(arg))
+                                return true;
 
-                return false;
-            }
+                        return false;
+                    }
 
-            return _policy.IsBlocked((Cts.MetadataType)type);
+                    return _policy.IsBlocked((Cts.MetadataType)type);
+            }            
         }
     }
 }