Added caching for Type.__ContainsMissingType property to simplify the prevention of infinite recursion while evaluating generic parameter constraints.

reflect/Reader/GenericTypeParameter.cs

@@ -88,58 +88,20 @@ namespace IKVM.Reflection.Reader
 			get { return true; }
 		}
 
-		public sealed override bool __ContainsMissingType
+		protected sealed override bool ContainsMissingTypeImpl
 		{
 			get
 			{
-				bool freeList = false;
-				try
+				foreach (Type type in GetGenericParameterConstraints())
 				{
-					foreach (Type type in GetGenericParameterConstraints())
+					if (type.__ContainsMissingType)
 					{
-						if (type.__IsMissing)
-						{
-							return true;
-						}
-						else if (type.IsConstructedGenericType || type.HasElementType || type.__IsFunctionPointer)
-						{
-							// if a constructed type contains generic parameters,
-							// it might contain this type parameter again and
-							// to prevent infinite recurssion, we keep a thread local
-							// list of type parameters we've already processed
-							if (type.ContainsGenericParameters)
-							{
-								if (containsMissingTypeHack == null)
-								{
-									freeList = true;
-									containsMissingTypeHack = new List<Type>();
-								}
-								else if (containsMissingTypeHack.Contains(this))
-								{
-									return false;
-								}
-								containsMissingTypeHack.Add(this);
-							}
-							if (type.__ContainsMissingType)
-							{
-								return true;
-							}
-						}
-					}
-					return false;
-				}
-				finally
-				{
-					if (freeList)
-					{
-						containsMissingTypeHack = null;
+						return true;
 					}
 				}
+				return false;
 			}
 		}
-
-		[ThreadStatic]
-		private static List<Type> containsMissingTypeHack;
 	}
 
 	sealed class UnboundGenericMethodParameter : TypeParameterType

reflect/Type.cs

@@ -67,6 +67,13 @@ namespace IKVM.Reflection
 
 			// for use by TypeDefImpl
 			NotGenericTypeDefinition = 128,
+
+			// used to cache __ContainsMissingType
+			ContainsMissingType_Unknown = 0,
+			ContainsMissingType_Pending = 256,
+			ContainsMissingType_Yes = 512,
+			ContainsMissingType_No = 1024,
+			ContainsMissingType_Mask = 256 | 512 | 1024,
 		}
 
 		// prevent subclassing by outsiders
@@ -1342,7 +1349,22 @@ namespace IKVM.Reflection
 			get { return this.DeclaringType != null; }
 		}
 
-		public virtual bool __ContainsMissingType
+		public bool __ContainsMissingType
+		{
+			get
+			{
+				if ((typeFlags & TypeFlags.ContainsMissingType_Mask) == TypeFlags.ContainsMissingType_Unknown)
+				{
+					// Generic parameter constraints can refer back to the type parameter they are part of,
+					// so to prevent infinite recursion, we set the Pending flag during computation.
+					typeFlags |= TypeFlags.ContainsMissingType_Pending;
+					typeFlags = (typeFlags & ~TypeFlags.ContainsMissingType_Mask) | (ContainsMissingTypeImpl ? TypeFlags.ContainsMissingType_Yes : TypeFlags.ContainsMissingType_No);
+				}
+				return (typeFlags & TypeFlags.ContainsMissingType_Mask) == TypeFlags.ContainsMissingType_Yes;
+			}
+		}
+
+		protected virtual bool ContainsMissingTypeImpl
 		{
 			get
 			{
@@ -2136,7 +2158,7 @@ namespace IKVM.Reflection
 			}
 		}
 
-		public sealed override bool __ContainsMissingType
+		protected sealed override bool ContainsMissingTypeImpl
 		{
 			get
 			{
@@ -2898,7 +2920,7 @@ namespace IKVM.Reflection
 			}
 		}
 
-		public override bool __ContainsMissingType
+		protected override bool ContainsMissingTypeImpl
 		{
 			get
 			{