Add GetEffectiveBaseClass() and GetEffectiveInterfaceSet() to ITypeParameter, and fixed a bug in DefaultTypeParameter.IsReferenceType().

ICSharpCode.NRefactory.CSharp/Resolver/TypeInference.cs

@@ -866,6 +866,16 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			public override TypeKind Kind {
 				get { return TypeKind.TypeParameter; }
 			}
+			
+			IType ITypeParameter.GetEffectiveBaseClass(ITypeResolveContext context)
+			{
+				return KnownTypeReference.Object.Resolve(context);
+			}
+			
+			IEnumerable<IType> ITypeParameter.GetEffectiveInterfaceSet(ITypeResolveContext context)
+			{
+				return EmptyList<IType>.Instance;
+			}
 		}
 		#endregion
 		

ICSharpCode.NRefactory.Tests/CSharp/CSharpAmbienceTests.cs

@@ -171,7 +171,7 @@ namespace ICSharpCode.NRefactory.CSharp
 		#endregion
 		
 		#region Test types
-		#pragma warning disable 169
+		#pragma warning disable 169, 67
 		
 		class Test {}
 		

ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj

@@ -177,6 +177,7 @@
     <Compile Include="TypeSystem\SerializedCecilLoaderTests.cs" />
     <Compile Include="TypeSystem\StructureTests.cs" />
     <Compile Include="TypeSystem\TestInterningProvider.cs" />
+    <Compile Include="TypeSystem\TypeParameterTests.cs" />
     <Compile Include="TypeSystem\TypeSystemTests.cs" />
     <Compile Include="TypeSystem\TypeSystemTests.TestCase.cs" />
     <EmbeddedResource Include="TypeSystem\TypeSystemTests.TestCase.cs" />

ICSharpCode.NRefactory.Tests/TypeSystem/TypeParameterTests.cs

@@ -0,0 +1,87 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+using System.Collections.Generic;
+using ICSharpCode.NRefactory.TypeSystem.Implementation;
+using NUnit.Framework;
+
+namespace ICSharpCode.NRefactory.TypeSystem
+{
+	[TestFixture]
+	public class TypeParameterTests
+	{
+		[Test]
+		public void TypeParameterDerivingFromOtherTypeParameterDoesNotInheritReferenceConstraint()
+		{
+			// class C<T, U> where T : class where U : T
+			DefaultTypeDefinition c = new DefaultTypeDefinition(MinimalResolveContext.Instance, string.Empty, "C");
+			DefaultTypeParameter t = new DefaultTypeParameter(EntityType.TypeDefinition, 0, "T");
+			DefaultTypeParameter u = new DefaultTypeParameter(EntityType.TypeDefinition, 1, "U");
+			c.TypeParameters.Add(t);
+			c.TypeParameters.Add(u);
+			t.HasReferenceTypeConstraint = true;
+			u.Constraints.Add(t);
+			
+			// At runtime, we might have T=System.ValueType and U=int, so C# can't inherit the 'class' constraint
+			// from one type parameter to another.
+			Assert.AreEqual(true, t.IsReferenceType(MinimalResolveContext.Instance));
+			Assert.IsNull(u.IsReferenceType(MinimalResolveContext.Instance));
+		}
+		
+		[Test]
+		public void ValueTypeParameterDerivingFromReferenceTypeParameter()
+		{
+			// class C<T, U> where T : class where U : T
+			DefaultTypeDefinition c = new DefaultTypeDefinition(MinimalResolveContext.Instance, string.Empty, "C");
+			DefaultTypeParameter t = new DefaultTypeParameter(EntityType.TypeDefinition, 0, "T");
+			DefaultTypeParameter u = new DefaultTypeParameter(EntityType.TypeDefinition, 1, "U");
+			c.TypeParameters.Add(t);
+			c.TypeParameters.Add(u);
+			t.HasReferenceTypeConstraint = true;
+			u.HasValueTypeConstraint = true;
+			u.Constraints.Add(t);
+			
+			// At runtime, we might have T=System.ValueType and U=int, so C# can't inherit the 'class' constraint
+			// from one type parameter to another.
+			Assert.AreEqual(true, t.IsReferenceType(MinimalResolveContext.Instance));
+			Assert.AreEqual(false, u.IsReferenceType(MinimalResolveContext.Instance));
+		}
+		
+		[Test]
+		public void TypeParameterDerivingFromOtherTypeParameterInheritsEffectiveBaseClass()
+		{
+			// class C<T, U> where T : class where U : T
+			ITypeResolveContext context = CecilLoaderTests.Mscorlib;
+			DefaultTypeDefinition c = new DefaultTypeDefinition(CecilLoaderTests.Mscorlib, string.Empty, "C");
+			DefaultTypeParameter t = new DefaultTypeParameter(EntityType.TypeDefinition, 0, "T");
+			DefaultTypeParameter u = new DefaultTypeParameter(EntityType.TypeDefinition, 1, "U");
+			c.TypeParameters.Add(t);
+			c.TypeParameters.Add(u);
+			t.Constraints.Add(typeof(List<string>).ToTypeReference());
+			u.Constraints.Add(t);
+			
+			// At runtime, we might have T=System.ValueType and U=int, so C# can't inherit the 'class' constraint
+			// from one type parameter to another.
+			Assert.AreEqual(true, t.IsReferenceType(context));
+			Assert.AreEqual(true, u.IsReferenceType(context));
+			Assert.AreEqual("System.Collections.Generic.List`1[[System.String]]", t.GetEffectiveBaseClass(context).ReflectionName);
+			Assert.AreEqual("System.Collections.Generic.List`1[[System.String]]", u.GetEffectiveBaseClass(context).ReflectionName);
+		}
+	}
+}

ICSharpCode.NRefactory/TypeSystem/ITypeParameter.cs

@@ -76,6 +76,16 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// Gets the region where the type parameter is defined.
 		/// </summary>
 		DomRegion Region { get; }
+		
+		/// <summary>
+		/// Gets the effective base class of this type parameter.
+		/// </summary>
+		IType GetEffectiveBaseClass(ITypeResolveContext context);
+		
+		/// <summary>
+		/// Gets the effective interface set of this type parameter.
+		/// </summary>
+		IEnumerable<IType> GetEffectiveInterfaceSet(ITypeResolveContext context);
 	}
 	
 	/// <summary>
@@ -165,6 +175,18 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		DomRegion ITypeParameter.Region {
 			get { return DomRegion.Empty; }
 		}
+		
+		IType ITypeParameter.GetEffectiveBaseClass(ITypeResolveContext context)
+		{
+			Contract.Requires(context != null);
+			Contract.Ensures(Contract.Result<IType>() != null);
+		}
+		
+		IEnumerable<IType> ITypeParameter.GetEffectiveInterfaceSet(ITypeResolveContext context)
+		{
+			Contract.Requires(context != null);
+			Contract.Ensures(Contract.Result<IEnumerable<IType>>() != null);
+		}
 	}
 	#endif
 }

ICSharpCode.NRefactory/TypeSystem/Implementation/DefaultTypeParameter.cs

@@ -99,23 +99,20 @@ namespace ICSharpCode.NRefactory.TypeSystem.Implementation
 				case FlagValueTypeConstraint:
 					return false;
 			}
-			// protect against cyclic dependencies between type parameters
-			using (var busyLock = BusyManager.Enter(this)) {
-				if (busyLock.Success) {
-					foreach (ITypeReference constraintRef in this.Constraints) {
-						IType constraint = constraintRef.Resolve(context);
-						ITypeDefinition constraintDef = constraint.GetDefinition();
-						// While interfaces are reference types, an interface constraint does not
-						// force the type parameter to be a reference type; so we need to explicitly look for classes here.
-						if (constraintDef != null && constraintDef.Kind == TypeKind.Class)
-							return true;
-						if (constraint is ITypeParameter) {
-							bool? isReferenceType = constraint.IsReferenceType(context);
-							if (isReferenceType.HasValue)
-								return isReferenceType.Value;
-						}
+			
+			// A type parameter is known to be a reference type if it has the reference type constraint
+			// or its effective base class is not object or System.ValueType.
+			IType baseClass = GetEffectiveBaseClass(context);
+			if (baseClass.Kind == TypeKind.Class) {
+				if (baseClass.Namespace == "System" && baseClass.TypeParameterCount == 0) {
+					switch (baseClass.Name) {
+						case "Object":
+						case "ValueType":
+						case "Enum":
+							return null;
 					}
 				}
+				return true;
 			}
 			return null;
 		}
@@ -333,6 +330,58 @@ namespace ICSharpCode.NRefactory.TypeSystem.Implementation
 			return EmptyList<IType>.Instance;
 		}
 		
+		public IType GetEffectiveBaseClass(ITypeResolveContext context)
+		{
+			// protect against cyclic type parameters
+			using (var busyLock = BusyManager.Enter(this)) {
+				if (!busyLock.Success)
+					return SharedTypes.UnknownType;
+				
+				if (HasValueTypeConstraint)
+					return context.GetTypeDefinition("System", "ValueType", 0, StringComparer.Ordinal) ?? SharedTypes.UnknownType;
+				
+				List<IType> classTypeConstraints = new List<IType>();
+				foreach (ITypeReference constraintRef in this.Constraints) {
+					IType constraint = constraintRef.Resolve(context);
+					if (constraint.Kind == TypeKind.Class) {
+						classTypeConstraints.Add(constraint);
+					} else if (constraint.Kind == TypeKind.TypeParameter) {
+						IType baseClass = ((ITypeParameter)constraint).GetEffectiveBaseClass(context);
+						if (baseClass.Kind == TypeKind.Class)
+							classTypeConstraints.Add(baseClass);
+					}
+				}
+				if (classTypeConstraints.Count == 0)
+					return KnownTypeReference.Object.Resolve(context);
+				// Find the derived-most type in the resulting set:
+				IType result = classTypeConstraints[0];
+				for (int i = 1; i < classTypeConstraints.Count; i++) {
+					if (classTypeConstraints[i].GetDefinition().IsDerivedFrom(result.GetDefinition(), context))
+						result = classTypeConstraints[i];
+				}
+				return result;
+			}
+		}
+		
+		public IEnumerable<IType> GetEffectiveInterfaceSet(ITypeResolveContext context)
+		{
+			List<IType> result = new List<IType>();
+			// protect against cyclic type parameters
+			using (var busyLock = BusyManager.Enter(this)) {
+				if (busyLock.Success) {
+					foreach (ITypeReference constraintRef in this.Constraints) {
+						IType constraint = constraintRef.Resolve(context);
+						if (constraint.Kind == TypeKind.Interface) {
+							result.Add(constraint);
+						} else if (constraint.Kind == TypeKind.TypeParameter) {
+							result.AddRange(((ITypeParameter)constraint).GetEffectiveInterfaceSet(context));
+						}
+					}
+				}
+			}
+			return result.Distinct();
+		}
+		
 		public IEnumerable<IType> GetBaseTypes(ITypeResolveContext context)
 		{
 			bool hasNonInterfaceConstraint = false;