#907: CallBuilder: If type arguments cannot be inferred from the parameter list, add them before asking overload resolution, but remove them again, if it does not reduce the number of casts.

ICSharpCode.Decompiler.Tests/TestCases/Pretty/ExpressionTrees.cs

@@ -474,53 +474,53 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		public static void ArrayIndexer()
 		{
-			Test((Func<int[], int>)((int[] array) => array[0]), (Expression<Func<int[], int>>)((int[] array) => array[0]));
-			Test((Func<int[], int, int>)((int[] array, int index) => array[index]), (Expression<Func<int[], int, int>>)((int[] array, int index) => array[index]));
-			Test((Func<int[,], int>)((int[,] array) => array[0, 5]), (Expression<Func<int[,], int>>)((int[,] array) => array[0, 5]));
-			Test((Func<int[,], int, int>)((int[,] array, int index) => array[index, 7]), (Expression<Func<int[,], int, int>>)((int[,] array, int index) => array[index, 7]));
-			Test((Func<int[][], int, int>)((int[][] array, int index) => array[index][7]), (Expression<Func<int[][], int, int>>)((int[][] array, int index) => array[index][7]));
+			Test<Func<int[], int>>((int[] array) => array[0], (int[] array) => array[0]);
+			Test<Func<int[], int, int>>((int[] array, int index) => array[index], (int[] array, int index) => array[index]);
+			Test<Func<int[,], int>>((int[,] array) => array[0, 5], (int[,] array) => array[0, 5]);
+			Test<Func<int[,], int, int>>((int[,] array, int index) => array[index, 7], (int[,] array, int index) => array[index, 7]);
+			Test<Func<int[][], int, int>>((int[][] array, int index) => array[index][7], (int[][] array, int index) => array[index][7]);
 		}
 
 		public static void ArrayLength()
 		{
-			Test((Func<int[], int>)((int[] array) => array.Length), (Expression<Func<int[], int>>)((int[] array) => array.Length));
-			Test((Func<int>)(() => ((Array)null).Length), (Expression<Func<int>>)(() => ((Array)null).Length));
+			Test<Func<int[], int>>((int[] array) => array.Length, (int[] array) => array.Length);
+			Test<Func<int>>(() => ((Array)null).Length, () => ((Array)null).Length);
 		}
 
 		public static void NewObj()
 		{
-			Test((Func<object>)(() => new SimpleType()), (Expression<Func<object>>)(() => new SimpleType()));
-			Test((Func<object>)(() => new SimpleTypeWithCtor(5)), (Expression<Func<object>>)(() => new SimpleTypeWithCtor(5)));
-			Test((Func<object>)(() => new SimpleTypeWithMultipleCtors()), (Expression<Func<object>>)(() => new SimpleTypeWithMultipleCtors()));
-			Test((Func<object>)(() => new SimpleTypeWithMultipleCtors(5)), (Expression<Func<object>>)(() => new SimpleTypeWithMultipleCtors(5)));
-			Test((Func<object>)(() => new GenericClass<int>()), (Expression<Func<object>>)(() => new GenericClass<int>()));
-			Test((Func<object>)(() => new GenericClassWithCtor<int>()), (Expression<Func<object>>)(() => new GenericClassWithCtor<int>()));
-			Test((Func<object>)(() => new GenericClassWithMultipleCtors<int>(5)), (Expression<Func<object>>)(() => new GenericClassWithMultipleCtors<int>(5)));
+			Test<Func<object>>(() => new SimpleType(), () => new SimpleType());
+			Test<Func<object>>(() => new SimpleTypeWithCtor(5), () => new SimpleTypeWithCtor(5));
+			Test<Func<object>>(() => new SimpleTypeWithMultipleCtors(), () => new SimpleTypeWithMultipleCtors());
+			Test<Func<object>>(() => new SimpleTypeWithMultipleCtors(5), () => new SimpleTypeWithMultipleCtors(5));
+			Test<Func<object>>(() => new GenericClass<int>(), () => new GenericClass<int>());
+			Test<Func<object>>(() => new GenericClassWithCtor<int>(), () => new GenericClassWithCtor<int>());
+			Test<Func<object>>(() => new GenericClassWithMultipleCtors<int>(5), () => new GenericClassWithMultipleCtors<int>(5));
 		}
 
 		public unsafe static void TypeOfExpr()
 		{
-			Test((Func<Type>)(() => typeof(int)), (Expression<Func<Type>>)(() => typeof(int)));
-			Test((Func<Type>)(() => typeof(object)), (Expression<Func<Type>>)(() => typeof(object)));
-			Test((Func<Type>)(() => typeof(List<>)), (Expression<Func<Type>>)(() => typeof(List<>)));
-			Test((Func<Type>)(() => typeof(List<int>)), (Expression<Func<Type>>)(() => typeof(List<int>)));
-			Test((Func<Type>)(() => typeof(int*)), (Expression<Func<Type>>)(() => typeof(int*)));
+			Test<Func<Type>>(() => typeof(int), () => typeof(int));
+			Test<Func<Type>>(() => typeof(object), () => typeof(object));
+			Test<Func<Type>>(() => typeof(List<>), () => typeof(List<>));
+			Test<Func<Type>>(() => typeof(List<int>), () => typeof(List<int>));
+			Test<Func<Type>>(() => typeof(int*), () => typeof(int*));
 		}
 
 		public static void AsTypeExpr()
 		{
-			Test((Func<object, MyClass>)((object obj) => obj as MyClass), (Expression<Func<object, MyClass>>)((object obj) => obj as MyClass));
-			Test((Func<object, GenericClass<object>>)((object obj) => obj as GenericClass<object>), (Expression<Func<object, GenericClass<object>>>)((object obj) => obj as GenericClass<object>));
+			Test<Func<object, MyClass>>((object obj) => obj as MyClass, (object obj) => obj as MyClass);
+			Test<Func<object, GenericClass<object>>>((object obj) => obj as GenericClass<object>, (object obj) => obj as GenericClass<object>);
 		}
 
 		public static void IsTypeExpr()
 		{
-			Test((Func<object, bool>)((object obj) => obj is MyClass), (Expression<Func<object, bool>>)((object obj) => obj is MyClass));
+			Test<Func<object, bool>>((object obj) => obj is MyClass, (object obj) => obj is MyClass);
 		}
 
 		public static void UnaryLogicalOperators()
 		{
-			Test((Func<bool, bool>)((bool a) => !a), (Expression<Func<bool, bool>>)((bool a) => !a));
+			Test<Func<bool, bool>>((bool a) => !a, (bool a) => !a);
 		}
 
 		public static void ConditionalOperator()
@@ -552,55 +552,55 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		public static void UnaryArithmeticOperators()
 		{
-			Test((Func<int, int>)((int a) => a), (Expression<Func<int, int>>)((int a) => a));
-			Test((Func<int, int>)((int a) => -a), (Expression<Func<int, int>>)((int a) => -a));
+			Test<Func<int, int>>((int a) => a, (int a) => a);
+			Test<Func<int, int>>((int a) => -a, (int a) => -a);
 		}
 
 		public static void BinaryArithmeticOperators()
 		{
-			Test((Func<int, int, int>)((int a, int b) => a + b), (Expression<Func<int, int, int>>)((int a, int b) => a + b));
-			Test((Func<int, int, int>)((int a, int b) => a - b), (Expression<Func<int, int, int>>)((int a, int b) => a - b));
-			Test((Func<int, int, int>)((int a, int b) => a * b), (Expression<Func<int, int, int>>)((int a, int b) => a * b));
-			Test((Func<int, int, int>)((int a, int b) => a / b), (Expression<Func<int, int, int>>)((int a, int b) => a / b));
-			Test((Func<int, int, int>)((int a, int b) => a % b), (Expression<Func<int, int, int>>)((int a, int b) => a % b));
-			Test((Func<long, int, long>)((long a, int b) => a + b), (Expression<Func<long, int, long>>)((long a, int b) => a + (long)b));
-			Test((Func<long, int, long>)((long a, int b) => a - b), (Expression<Func<long, int, long>>)((long a, int b) => a - (long)b));
-			Test((Func<long, int, long>)((long a, int b) => a * b), (Expression<Func<long, int, long>>)((long a, int b) => a * (long)b));
-			Test((Func<long, int, long>)((long a, int b) => a / b), (Expression<Func<long, int, long>>)((long a, int b) => a / (long)b));
-			Test((Func<long, int, long>)((long a, int b) => a % b), (Expression<Func<long, int, long>>)((long a, int b) => a % (long)b));
-			Test((Func<short, int, int>)((short a, int b) => a + b), (Expression<Func<short, int, int>>)((short a, int b) => a + b));
-			Test((Func<int, short, int>)((int a, short b) => a - b), (Expression<Func<int, short, int>>)((int a, short b) => a - b));
-			Test((Func<short, int, int>)((short a, int b) => a * b), (Expression<Func<short, int, int>>)((short a, int b) => a * b));
-			Test((Func<int, short, int>)((int a, short b) => a / b), (Expression<Func<int, short, int>>)((int a, short b) => a / b));
-			Test((Func<short, int, int>)((short a, int b) => a % b), (Expression<Func<short, int, int>>)((short a, int b) => a % b));
+			Test<Func<int, int, int>>((int a, int b) => a + b, (int a, int b) => a + b);
+			Test<Func<int, int, int>>((int a, int b) => a - b, (int a, int b) => a - b);
+			Test<Func<int, int, int>>((int a, int b) => a * b, (int a, int b) => a * b);
+			Test<Func<int, int, int>>((int a, int b) => a / b, (int a, int b) => a / b);
+			Test<Func<int, int, int>>((int a, int b) => a % b, (int a, int b) => a % b);
+			Test<Func<long, int, long>>((long a, int b) => a + b, (long a, int b) => a + (long)b);
+			Test<Func<long, int, long>>((long a, int b) => a - b, (long a, int b) => a - (long)b);
+			Test<Func<long, int, long>>((long a, int b) => a * b, (long a, int b) => a * (long)b);
+			Test<Func<long, int, long>>((long a, int b) => a / b, (long a, int b) => a / (long)b);
+			Test<Func<long, int, long>>((long a, int b) => a % b, (long a, int b) => a % (long)b);
+			Test<Func<short, int, int>>((short a, int b) => a + b, (short a, int b) => a + b);
+			Test<Func<int, short, int>>((int a, short b) => a - b, (int a, short b) => a - b);
+			Test<Func<short, int, int>>((short a, int b) => a * b, (short a, int b) => a * b);
+			Test<Func<int, short, int>>((int a, short b) => a / b, (int a, short b) => a / b);
+			Test<Func<short, int, int>>((short a, int b) => a % b, (short a, int b) => a % b);
 		}
 
 		public static void BitOperators()
 		{
-			Test((Func<int, int>)((int a) => ~a), (Expression<Func<int, int>>)((int a) => ~a));
-			Test((Func<int, int, int>)((int a, int b) => a & b), (Expression<Func<int, int, int>>)((int a, int b) => a & b));
-			Test((Func<int, int, int>)((int a, int b) => a | b), (Expression<Func<int, int, int>>)((int a, int b) => a | b));
-			Test((Func<int, int, int>)((int a, int b) => a ^ b), (Expression<Func<int, int, int>>)((int a, int b) => a ^ b));
+			Test<Func<int, int>>((int a) => ~a, (int a) => ~a);
+			Test<Func<int, int, int>>((int a, int b) => a & b, (int a, int b) => a & b);
+			Test<Func<int, int, int>>((int a, int b) => a | b, (int a, int b) => a | b);
+			Test<Func<int, int, int>>((int a, int b) => a ^ b, (int a, int b) => a ^ b);
 		}
 
 		public static void ShiftOperators()
 		{
-			Test((Func<int, int>)((int a) => a >> 2), (Expression<Func<int, int>>)((int a) => a >> 2));
-			Test((Func<int, int>)((int a) => a << 2), (Expression<Func<int, int>>)((int a) => a << 2));
-			Test((Func<long, long>)((long a) => a >> 2), (Expression<Func<long, long>>)((long a) => a >> 2));
-			Test((Func<long, long>)((long a) => a << 2), (Expression<Func<long, long>>)((long a) => a << 2));
+			Test<Func<int, int>>((int a) => a >> 2, (int a) => a >> 2);
+			Test<Func<int, int>>((int a) => a << 2, (int a) => a << 2);
+			Test<Func<long, long>>((long a) => a >> 2, (long a) => a >> 2);
+			Test<Func<long, long>>((long a) => a << 2, (long a) => a << 2);
 		}
 
 		public static void SimpleExpressions()
 		{
-			Test((Func<int>)(() => 0), (Expression<Func<int>>)(() => 0));
-			Test((Func<int, int>)((int a) => a), (Expression<Func<int, int>>)((int a) => a));
+			Test<Func<int>>(() => 0, () => 0);
+			Test<Func<int, int>>((int a) => a, (int a) => a);
 		}
 
 		public static void Capturing()
 		{
 			int captured = 5;
-			Test((Func<int>)(() => captured), (Expression<Func<int>>)(() => captured));
+			Test<Func<int>>(() => captured, () => captured);
 		}
 
 		public static void FieldAndPropertyAccess()
@@ -619,55 +619,55 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		public static void Call()
 		{
 			ToCode(null, (string a) => Console.WriteLine(a));
-			Test((Func<string, string>)((string a) => a.ToString()), (Expression<Func<string, string>>)((string a) => a.ToString()));
-			Test((Func<int, string>)((int a) => a.ToString()), (Expression<Func<int, string>>)((int a) => a.ToString()));
-			Test((Func<string, char[]>)((string a) => a.ToArray()), (Expression<Func<string, char[]>>)((string a) => a.ToArray()));
-			Test((Func<bool>)(() => 'a'.CompareTo('b') < 0), (Expression<Func<bool>>)(() => 'a'.CompareTo('b') < 0));
+			Test<Func<string, string>>((string a) => a.ToString(), (string a) => a.ToString());
+			Test<Func<int, string>>((int a) => a.ToString(), (int a) => a.ToString());
+			Test<Func<string, char[]>>((string a) => a.ToArray(), (string a) => a.ToArray());
+			Test<Func<bool>>(() => 'a'.CompareTo('b') < 0, () => 'a'.CompareTo('b') < 0);
 		}
 
 		public static void Quote()
 		{
-			Test((Func<bool>)(() => (Expression<Func<int, string, string>>)((int n, string s) => s + n.ToString()) != null), (Expression<Func<bool>>)(() => (Expression<Func<int, string, string>>)((int n, string s) => s + n.ToString()) != null));
+			Test<Func<bool>>(() => (Expression<Func<int, string, string>>)((int n, string s) => s + n.ToString()) != null, () => (Expression<Func<int, string, string>>)((int n, string s) => s + n.ToString()) != null);
 		}
 
 		public static void ArrayInitializer()
 		{
-			Test((Func<int[]>)(() => new int[3] {
+			Test<Func<int[]>>(() => new int[3] {
 				1,
 				2,
 				3
-			}), (Expression<Func<int[]>>)(() => new int[3] {
+			}, () => new int[3] {
 				1,
 				2,
 				3
-			}));
-			Test((Func<int[]>)(() => new int[3]), (Expression<Func<int[]>>)(() => new int[3]));
-			Test((Func<int[,]>)(() => new int[3, 5]), (Expression<Func<int[,]>>)(() => new int[3, 5]));
-			Test((Func<int[][]>)(() => new int[3][]), (Expression<Func<int[][]>>)(() => new int[3][]));
-			Test((Func<int[][]>)(() => new int[1][] {
+			});
+			Test<Func<int[]>>(() => new int[3], () => new int[3]);
+			Test<Func<int[,]>>(() => new int[3, 5], () => new int[3, 5]);
+			Test<Func<int[][]>>(() => new int[3][], () => new int[3][]);
+			Test<Func<int[][]>>(() => new int[1][] {
 				new int[3] {
 					1,
 					2,
 					3
 				}
-			}), (Expression<Func<int[][]>>)(() => new int[1][] {
+			}, () => new int[1][] {
 				new int[3] {
 					1,
 					2,
 					3
 				}
-			}));
+			});
 		}
 
 		public static void AnonymousTypes()
 		{
-			Test((Func<object>)(() => new {
+			Test<Func<object>>(() => new {
 				A = 5,
 				B = "Test"
-			}), (Expression<Func<object>>)(() => new {
+			}, () => new {
 				A = 5,
 				B = "Test"
-			}));
+			});
 		}
 
 		public static void ObjectInit()

ICSharpCode.Decompiler/CSharp/CallBuilder.cs

@@ -383,8 +383,10 @@ namespace ICSharpCode.Decompiler.CSharp
 			List<IParameter> expectedParameters, CallTransformation allowedTransforms, out IParameterizedMember foundMethod)
 		{
 			CallTransformation transform = CallTransformation.None;
+
+			// initialize requireTarget flag
 			bool requireTarget;
-			bool requireTypeArguments = false;
+			ResolveResult targetResolveResult;
 			if ((allowedTransforms & CallTransformation.RequireTarget) != 0) {
 				if (expressionBuilder.HidesVariableWithName(method.Name)) {
 					requireTarget = true;
@@ -398,13 +400,41 @@ namespace ICSharpCode.Decompiler.CSharp
 					else
 						requireTarget = !(target.Expression is ThisReferenceExpression);
 				}
+				targetResolveResult = requireTarget ? target.ResolveResult : null;
 			} else {
+				// HACK: this is a special case for collection initializer calls, they do not allow a target to be
+				// emitted, but we still need it for overload resolution.
 				requireTarget = true;
+				targetResolveResult = target.ResolveResult;
+			}
+
+			// initialize requireTypeArguments flag
+			bool requireTypeArguments;
+			IType[] typeArguments;
+			bool appliedRequireTypeArgumentsShortcut = false;
+			if (method.TypeParameters.Count > 0 && (allowedTransforms & CallTransformation.RequireTypeArguments) != 0
+				&& !IsPossibleExtensionMethodCallOnNull(method, arguments)) {
+				// The ambiguity resolution below only adds type arguments as last resort measure, however there are
+				// methods, such as Enumerable.OfType<TResult>(IEnumerable input) that always require type arguments,
+				// as those cannot be inferred from the parameters, which leads to bloated expressions full of extra casts
+				// that are no longer required once we add the type arguments.
+				// We lend overload resolution a hand by detecting such cases beforehand and requiring type arguments,
+				// if necessary.
+				if (!CanInferTypeArgumentsFromParameters(method, arguments.SelectArray(a => a.ResolveResult), expressionBuilder.typeInference)) {
+					requireTypeArguments = true;
+					typeArguments = method.TypeArguments.ToArray();
+					appliedRequireTypeArgumentsShortcut = true;
+				} else {
+					requireTypeArguments = false;
+					typeArguments = Empty<IType>.Array;
+				}
+			} else {
+				requireTypeArguments = false;
+				typeArguments = Empty<IType>.Array;
 			}
+
 			bool targetCasted = false;
 			bool argumentsCasted = false;
-			IType[] typeArguments = Empty<IType>.Array;
-			var targetResolveResult = requireTarget ? target.ResolveResult : null;
 			OverloadResolutionErrors errors;
 			while ((errors = IsUnambiguousCall(expectedTargetDetails, method, targetResolveResult, typeArguments, arguments, argumentNames, out foundMethod)) != OverloadResolutionErrors.None) {
 				switch (errors) {
@@ -423,6 +453,13 @@ namespace ICSharpCode.Decompiler.CSharp
 						// TODO : implement some more intelligent algorithm that decides which of these fixes (cast args, add target, cast target, add type args)
 						// is best in this case. Additionally we should not cast all arguments at once, but step-by-step try to add only a minimal number of casts.
 						if (!argumentsCasted) {
+							// If we added type arguments beforehand, but that didn't make the code any better,
+							// undo that decision and add casts first.
+							if (appliedRequireTypeArgumentsShortcut) {
+								requireTypeArguments = false;
+								typeArguments = Empty<IType>.Array;
+								appliedRequireTypeArgumentsShortcut = false;
+							}
 							argumentsCasted = true;
 							CastArguments(arguments, expectedParameters);
 						} else if ((allowedTransforms & CallTransformation.RequireTarget) != 0 && !requireTarget) {
@@ -451,6 +488,23 @@ namespace ICSharpCode.Decompiler.CSharp
 			return transform;
 		}
 
+		private bool IsPossibleExtensionMethodCallOnNull(IMethod method, List<TranslatedExpression> arguments)
+		{
+			return method.IsExtensionMethod && arguments.Count > 0 && arguments[0].Expression is NullReferenceExpression;
+		}
+
+		public static bool CanInferTypeArgumentsFromParameters(IMethod method, IReadOnlyList<ResolveResult> arguments,
+			TypeInference typeInference)
+		{
+			if (method.TypeParameters.Count == 0)
+				return true;
+			// always use unspecialized member, otherwise type inference fails
+			method = (IMethod)method.MemberDefinition;
+			typeInference.InferTypeArguments(method.TypeParameters, arguments, method.Parameters.SelectArray(p => p.Type),
+				out bool success);
+			return success;
+		}
+
 		private void CastArguments(IList<TranslatedExpression> arguments, IReadOnlyList<IParameter> expectedParameters)
 		{
 			for (int i = 0; i < arguments.Count; i++) {
@@ -574,7 +628,7 @@ namespace ICSharpCode.Decompiler.CSharp
 					return OverloadResolutionErrors.AmbiguousMatch;
 				or.AddMethodLists(result.MethodsGroupedByDeclaringType.ToArray());
 			} else {
-				var result = lookup.Lookup(target, method.Name, EmptyList<IType>.Instance, isInvocation: true) as MethodGroupResolveResult;
+				var result = lookup.Lookup(target, method.Name, typeArguments, isInvocation: true) as MethodGroupResolveResult;
 				if (result == null)
 					return OverloadResolutionErrors.AmbiguousMatch;
 				or.AddMethodLists(result.MethodsGroupedByDeclaringType.ToArray());

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -73,7 +73,7 @@ namespace ICSharpCode.Decompiler.CSharp
 		internal readonly ICompilation compilation;
 		internal readonly CSharpResolver resolver;
 		readonly TypeSystemAstBuilder astBuilder;
-		readonly TypeInference typeInference;
+		internal readonly TypeInference typeInference;
 		internal readonly DecompilerSettings settings;
 		readonly CancellationToken cancellationToken;
 		

ICSharpCode.Decompiler/CSharp/Transforms/IntroduceExtensionMethods.cs

@@ -18,6 +18,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using ICSharpCode.Decompiler.CSharp.Resolver;
 using ICSharpCode.Decompiler.CSharp.Syntax;
@@ -136,8 +137,10 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			}
 			if (!CanTransformToExtensionMethodCall(resolver, method, typeArguments, target, args, argNames))
 				return;
-			if (firstArgument is NullReferenceExpression)
+			if (firstArgument is NullReferenceExpression) {
+				Debug.Assert(context.RequiredNamespacesSuperset.Contains(method.Parameters[0].Type.Namespace));
 				firstArgument = firstArgument.ReplaceWith(expr => new CastExpression(context.TypeSystemAstBuilder.ConvertType(method.Parameters[0].Type), expr.Detach()));
+			}
 			if (invocationExpression.Target is IdentifierExpression identifierExpression) {
 				identifierExpression.Detach();
 				memberRefExpr = new MemberReferenceExpression(firstArgument.Detach(), method.Name, identifierExpression.TypeArguments.Detach());
@@ -169,14 +172,5 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			var resolver = new CSharpResolver(resolveContext);
 			return CanTransformToExtensionMethodCall(resolver, method, typeArgs, targetType, paramTypes, argumentNames: paramNames);
 		}
-
-		public static bool CanInferTypeArgumentsFromParameters(IMethod method, IReadOnlyList<ResolveResult> arguments, ITypeResolveContext resolveContext)
-		{
-			if (method.TypeParameters.Count == 0)
-				return true;
-			var inference = new TypeInference(resolveContext.Compilation);
-			inference.InferTypeArguments(method.TypeParameters, arguments, method.Parameters.SelectArray(p => p.Type), out bool success);
-			return success;
-		}
 	}
 }

ICSharpCode.Decompiler/IL/Transforms/TransformCollectionAndObjectInitializers.cs

@@ -350,7 +350,9 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				return false;
 			if (!targetType.GetAllBaseTypes().Any(i => i.IsKnownType(KnownTypeCode.IEnumerable) || i.IsKnownType(KnownTypeCode.IEnumerableOfT)))
 				return false;
-			return CSharp.Transforms.IntroduceExtensionMethods.CanInferTypeArgumentsFromParameters(method, method.Parameters.SelectArray(p => new ResolveResult(p.Type)), resolveContext);
+			return CSharp.CallBuilder.CanInferTypeArgumentsFromParameters(
+				method, method.Parameters.SelectArray(p => new ResolveResult(p.Type)),
+				new TypeInference(resolveContext.Compilation));
 		}
 
 		static IType GetReturnTypeFromInstruction(ILInstruction instruction)