Implemented eligibility check for extension methods.

ICSharpCode.NRefactory.CSharp/Completion/CSharpCompletionEngine.cs

@@ -1,4 +1,4 @@
-// 
+// 
 // CSharpCompletionEngine.cs
 //  
 // Author:
@@ -1778,7 +1778,7 @@ namespace ICSharpCode.NRefactory.CSharp.Completion
 				}
 				
 			} else {
-				foreach (var meths in state.GetAllExtensionMethods (type)) {
+				foreach (var meths in state.GetExtensionMethods (type)) {
 					foreach (var m in meths) {
 						result.AddMember (m);
 					}

ICSharpCode.NRefactory.CSharp/Resolver/CSharpAstResolver.cs

@@ -59,7 +59,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		/// <summary>
 		/// Creates a new C# AST resolver.
 		/// </summary>
-		/// <param name="resolver">The resolver state at the root node.</param>
+		/// <param name="resolver">The resolver state at the root node (to be more precise: outside the root node).</param>
 		/// <param name="rootNode">The root node of the resolved tree.</param>
 		/// <param name="parsedFile">The parsed file for the nodes being resolved. This parameter is used only
 		/// when the root node is on the type level; it is not necessary when an expression is passed.

ICSharpCode.NRefactory.CSharp/Resolver/CSharpResolver.cs

@@ -1530,7 +1530,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			MemberLookup lookup = CreateMemberLookup();
 			ResolveResult result = lookup.Lookup(target, identifier, typeArguments, isInvocationTarget);
 			if (result is UnknownMemberResolveResult) {
-				var extensionMethods = GetExtensionMethods(target.Type, identifier, typeArguments);
+				var extensionMethods = GetExtensionMethods(identifier, typeArguments);
 				if (extensionMethods.Count > 0) {
 					return new MethodGroupResolveResult(target, identifier, EmptyList<MethodListWithDeclaringType>.Instance, typeArguments) {
 						extensionMethods = extensionMethods
@@ -1599,12 +1599,34 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		#endregion
 		
 		#region GetExtensionMethods
+		/// <summary>
+		/// Gets all extension methods that are available in the current context.
+		/// </summary>
+		/// <param name="name">Name of the extension method. Pass null to retrieve all extension methods.</param>
+		/// <param name="typeArguments">Explicitly provided type arguments.
+		/// An empty list will return all matching extension method definitions;
+		/// a non-empty list will return <see cref="SpecializedMethod"/>s for all extension methods
+		/// with the matching number of type parameters.</param>
+		/// <remarks>
+		/// The results are stored in nested lists because they are grouped by using scope.
+		/// That is, for "using SomeExtensions; namespace X { using MoreExtensions; ... }",
+		/// the return value will be
+		/// new List {
+		///    new List { all extensions from MoreExtensions },
+		///    new List { all extensions from SomeExtensions }
+		/// }
+		/// </remarks>
+		public List<List<IMethod>> GetExtensionMethods(string name = null, IList<IType> typeArguments = null)
+		{
+			return GetExtensionMethods(null, name, typeArguments);
+		}
+		
 		/// <summary>
 		/// Gets the extension methods that are called 'name'
 		/// and are applicable with a first argument type of 'targetType'.
 		/// </summary>
 		/// <param name="targetType">Type of the 'this' argument</param>
-		/// <param name="name">Name of the extension method</param>
+		/// <param name="name">Name of the extension method. Pass null to retrieve all extension methods.</param>
 		/// <param name="typeArguments">Explicitly provided type arguments.
 		/// An empty list will return all matching extension method definitions;
 		/// a non-empty list will return <see cref="SpecializedMethod"/>s for all extension methods
@@ -1618,24 +1640,24 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		///    new List { all extensions from SomeExtensions }
 		/// }
 		/// </remarks>
-		public List<List<IMethod>> GetExtensionMethods(IType targetType, string name, IList<IType> typeArguments = null)
+		public List<List<IMethod>> GetExtensionMethods(IType targetType, string name = null, IList<IType> typeArguments = null)
 		{
 			List<List<IMethod>> extensionMethodGroups = new List<List<IMethod>>();
 			foreach (var inputGroup in GetAllExtensionMethods()) {
 				List<IMethod> outputGroup = new List<IMethod>();
 				foreach (var method in inputGroup) {
-					if (method.Name != name)
+					if (name != null && method.Name != name)
 						continue;
 					
 					if (typeArguments != null && typeArguments.Count > 0) {
 						if (method.TypeParameters.Count != typeArguments.Count)
 							continue;
 						SpecializedMethod sm = new SpecializedMethod(method.DeclaringType, method, typeArguments);
-						// TODO: verify targetType
-						outputGroup.Add(sm);
+						if (IsEligibleExtensionMethod(targetType, method, false))
+							outputGroup.Add(sm);
 					} else {
-						// TODO: verify targetType
-						outputGroup.Add(method);
+						if (IsEligibleExtensionMethod(targetType, method, true))
+							outputGroup.Add(method);
 					}
 				}
 				if (outputGroup.Count > 0)
@@ -1644,22 +1666,34 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			return extensionMethodGroups;
 		}
 		
-		public List<List<IMethod>> GetAllExtensionMethods(IType targetType)
+		bool IsEligibleExtensionMethod(IType targetType, IMethod method, bool useTypeInference)
 		{
-			List<List<IMethod>> extensionMethodGroups = new List<List<IMethod>>();
-			foreach (var inputGroup in GetAllExtensionMethods()) {
-				List<IMethod> outputGroup = new List<IMethod>();
-				foreach (var method in inputGroup) {
-					outputGroup.Add(method);
+			if (targetType == null)
+				return true;
+			if (method.Parameters.Count == 0)
+				return false;
+			IType thisParameterType = method.Parameters[0].Type;
+			if (useTypeInference && method.TypeParameters.Count > 0) {
+				// We need to infer type arguments from targetType:
+				TypeInference ti = new TypeInference(compilation, conversions);
+				ResolveResult[] arguments = { new ResolveResult(targetType) };
+				IType[] parameterTypes = { method.Parameters[0].Type };
+				bool success;
+				IType[] inferredTypes = ti.InferTypeArguments(method.TypeParameters, arguments, parameterTypes, out success);
+				var substitution = new TypeParameterSubstitution(null, inferredTypes);
+				// Validate that the types that could be inferred (aren't unknown) satisfy the constraints:
+				for (int i = 0; i < inferredTypes.Length; i++) {
+					if (inferredTypes[i].Kind != TypeKind.Unknown && inferredTypes[i].Kind != TypeKind.UnboundTypeArgument) {
+						if (!OverloadResolution.ValidateConstraints(method.TypeParameters[i], inferredTypes[i], substitution, conversions))
+							return false;
+					}
 				}
-				if (outputGroup.Count > 0)
-					extensionMethodGroups.Add(outputGroup);
+				thisParameterType = thisParameterType.AcceptVisitor(substitution);
 			}
-			return extensionMethodGroups;
+			Conversion c = conversions.ImplicitConversion(targetType, thisParameterType);
+			return c.IsValid && (c.IsIdentityConversion || c.IsReferenceConversion || c.IsBoxingConversion);
 		}
 		
-		//
-		
 		/// <summary>
 		/// Gets all extension methods available in the current using scope.
 		/// This list includes unaccessible

ICSharpCode.NRefactory.CSharp/Resolver/MethodGroupResolveResult.cs

@@ -126,6 +126,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		
 		/// <summary>
 		/// Gets all candidate extension methods.
+		/// Note: this includes candidates that are not eligible due to a
 		/// </summary>
 		/// <remarks>
 		/// The results are stored in nested lists because they are grouped by using scope.
@@ -141,7 +142,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			if (resolver != null) {
 				Debug.Assert(extensionMethods == null);
 				try {
-					extensionMethods = resolver.GetExtensionMethods(this.TargetType, methodName, typeArguments);
+					extensionMethods = resolver.GetExtensionMethods(methodName, typeArguments);
 				} finally {
 					resolver = null;
 				}

ICSharpCode.NRefactory.CSharp/Resolver/OverloadResolution.cs

@@ -418,36 +418,11 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 					if (newParameterizedType != null) {
 						// C# 4.0 spec: §4.4.4 Satisfying constraints
 						var typeParameters = newParameterizedType.GetDefinition().TypeParameters;
+						var substitution = newParameterizedType.GetSubstitution();
 						for (int i = 0; i < typeParameters.Count; i++) {
-							ITypeParameter tp = typeParameters[i];
-							IType typeArg = newParameterizedType.GetTypeArgument(i);
-							switch (typeArg.Kind) { // void, null, and pointers cannot be used as type arguments
-								case TypeKind.Void:
-								case TypeKind.Null:
-								case TypeKind.Pointer:
-									ConstraintsValid = false;
-									break;
-							}
-							if (tp.HasReferenceTypeConstraint) {
-								if (typeArg.IsReferenceType != true)
-									ConstraintsValid = false;
-							}
-							if (tp.HasValueTypeConstraint) {
-								if (!NullableType.IsNonNullableValueType(typeArg))
-									ConstraintsValid = false;
-							}
-							if (tp.HasDefaultConstructorConstraint) {
-								ITypeDefinition def = typeArg.GetDefinition();
-								if (def != null && def.IsAbstract)
-									ConstraintsValid = false;
-								ConstraintsValid &= typeArg.GetConstructors(
-									m => m.Parameters.Count == 0 && m.Accessibility == Accessibility.Public,
-									GetMemberOptions.IgnoreInheritedMembers | GetMemberOptions.ReturnMemberDefinitions
-								).Any();
-							}
-							foreach (IType constraintType in tp.DirectBaseTypes) {
-								IType c = constraintType.AcceptVisitor(newParameterizedType.GetSubstitution());
-								ConstraintsValid &= conversions.IsConstraintConvertible(typeArg, c);
+							if (!ValidateConstraints(typeParameters[i], newParameterizedType.GetTypeArgument(i), substitution, conversions)) {
+								ConstraintsValid = false;
+								break;
 							}
 						}
 					}
@@ -457,6 +432,64 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		}
 		#endregion
 		
+		#region Validate Constraints
+		/// <summary>
+		/// Validates whether the given type argument satisfies the constraints for the given type parameter.
+		/// </summary>
+		/// <param name="typeParameter">The type parameter.</param>
+		/// <param name="typeArgument">The type argument.</param>
+		/// <param name="substitution">The substitution that defines how type parameters are replaced with type arguments.
+		/// The substitution is used to check constraints that depend on other type parameters (or recursively on the same type parameter).</param>
+		/// <returns>True if the constraints are satisfied; false otherwise.</returns>
+		public static bool ValidateConstraints(ITypeParameter typeParameter, IType typeArgument, TypeVisitor substitution)
+		{
+			if (typeParameter == null)
+				throw new ArgumentNullException("typeParameter");
+			if (typeParameter.Owner == null)
+				throw new ArgumentNullException("typeParameter.Owner");
+			if (typeArgument == null)
+				throw new ArgumentNullException("typeArgument");
+			return ValidateConstraints(typeParameter, typeArgument, substitution, Conversions.Get(typeParameter.Owner.Compilation));
+		}
+		
+		internal static bool ValidateConstraints(ITypeParameter typeParameter, IType typeArgument, TypeVisitor substitution, Conversions conversions)
+		{
+			switch (typeArgument.Kind) { // void, null, and pointers cannot be used as type arguments
+				case TypeKind.Void:
+				case TypeKind.Null:
+				case TypeKind.Pointer:
+					return false;
+			}
+			if (typeParameter.HasReferenceTypeConstraint) {
+				if (typeArgument.IsReferenceType != true)
+					return false;
+			}
+			if (typeParameter.HasValueTypeConstraint) {
+				if (!NullableType.IsNonNullableValueType(typeArgument))
+					return false;
+			}
+			if (typeParameter.HasDefaultConstructorConstraint) {
+				ITypeDefinition def = typeArgument.GetDefinition();
+				if (def != null && def.IsAbstract)
+					return false;
+				var ctors = typeArgument.GetConstructors(
+					m => m.Parameters.Count == 0 && m.Accessibility == Accessibility.Public,
+					GetMemberOptions.IgnoreInheritedMembers | GetMemberOptions.ReturnMemberDefinitions
+				);
+				if (!ctors.Any())
+					return false;
+			}
+			foreach (IType constraintType in typeParameter.DirectBaseTypes) {
+				IType c = constraintType;
+				if (substitution != null)
+					c = c.AcceptVisitor(substitution);
+				if (!conversions.IsConstraintConvertible(typeArgument, c))
+					return false;
+			}
+			return true;
+		}
+		#endregion
+		
 		#region CheckApplicability
 		void CheckApplicability(Candidate candidate)
 		{