Revert f01a4b2 and 58c4ec8.

Fixed small issue in CSharpResolver.GetExtensionMethods: when type parameters are provided explicitly, use the specialized method for the eligibility check.

ICSharpCode.NRefactory.CSharp/Resolver/CSharpResolver.cs

@@ -1618,7 +1618,11 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 					throw new NotSupportedException("Invalid value for NameLookupMode");
 			}
 			if (result is UnknownMemberResolveResult) {
-				var extensionMethods = GetExtensionMethods(target.Type, identifier, typeArguments, true);
+				// We intentionally use all extension methods here, not just the eligible ones.
+				// Proper eligibility checking is only possible for the full invocation
+				// (after we know the remaining arguments).
+				// The eligibility check in GetExtensionMethods is only intended for code completion.
+				var extensionMethods = GetExtensionMethods(identifier, typeArguments);
 				if (extensionMethods.Count > 0) {
 					return new MethodGroupResolveResult(target, identifier, EmptyList<MethodListWithDeclaringType>.Instance, typeArguments) {
 						extensionMethods = extensionMethods
@@ -1755,7 +1759,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 						if (method.TypeParameters.Count != typeArguments.Count)
 							continue;
 						SpecializedMethod sm = new SpecializedMethod(method, new TypeParameterSubstitution(null, typeArguments));
-						if (IsEligibleExtensionMethod(compilation, conversions, targetType, method, true, out inferredTypes))
+						if (IsEligibleExtensionMethod(compilation, conversions, targetType, sm, false, out inferredTypes))
 							outputGroup.Add(sm);
 					} else {
 						if (IsEligibleExtensionMethod(compilation, conversions, targetType, method, true, out inferredTypes)) {

ICSharpCode.NRefactory.CSharp/Resolver/MethodGroupResolveResult.cs

@@ -132,6 +132,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		/// Gets all candidate extension methods.
 		/// Note: this includes candidates that are not eligible due to an inapplicable
 		/// this argument.
+		/// The candidates will only be specialized if the type arguments were provided explicitly.
 		/// </summary>
 		/// <remarks>
 		/// The results are stored in nested lists because they are grouped by using scope.
@@ -155,6 +156,24 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			return extensionMethods ?? Enumerable.Empty<IEnumerable<IMethod>>();
 		}
 		
+		/// <summary>
+		/// Gets the eligible extension methods.
+		/// </summary>
+		/// <param name="substituteInferredTypes">
+		/// Specifies whether to produce a <see cref="SpecializedMethod"/>
+		/// when type arguments could be inferred from <paramref name="targetType"/>. This parameter
+		/// is only used for inferred types and has no effect if the type parameters are
+		/// specified explicitly.
+		/// </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 IEnumerable<IEnumerable<IMethod>> GetEligibleExtensionMethods(bool substituteInferredTypes)
 		{
 			var result = new List<List<IMethod>>();

ICSharpCode.NRefactory.Tests/CSharp/Resolver/ExtensionMethodTests.cs

@@ -17,8 +17,10 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
+using System.Linq;
 using ICSharpCode.NRefactory.Semantics;
 using ICSharpCode.NRefactory.TypeSystem;
+using ICSharpCode.NRefactory.TypeSystem.Implementation;
 using NUnit.Framework;
 
 namespace ICSharpCode.NRefactory.CSharp.Resolver
@@ -118,5 +120,83 @@ public static class XC {
 			Assert.AreEqual(1, inferredTypes.Length);
 			Assert.AreEqual("System.String", inferredTypes[0].ReflectionName);
 		}
+		
+		
+		[Test]
+		public void InferTypeFromOverwrittenMethodArguments()
+		{
+			string program = @"using System.Collections.Generic;
+		using System.Linq;
+		
+		public class A { }
+		
+		public class B : A { }
+		
+		class Program
+		{
+			static void Main(string[] args)
+			{
+				IEnumerable<B> list = new List<B>();
+				var arr = $list.ToArray<A>()$;
+			}
+		}
+";
+			var rr = Resolve<CSharpInvocationResolveResult>(program);
+			Assert.AreEqual("A[]", rr.Type.ReflectionName);
+			Assert.AreEqual("System.Linq.Enumerable.ToArray", rr.Member.FullName);
+			Assert.AreEqual("A", ((SpecializedMethod)rr.Member).TypeArguments.Single().ReflectionName);
+		}
+		
+		[Test]
+		public void TypeInferenceBasedOnTargetTypeAndArgumentType()
+		{
+			string program = @"using System.Collections.Generic;
+		using System.Linq;
+		
+		public class A { }
+		public class B : A { }
+		
+		static class Program
+		{
+			static void Main(A a, B b)
+			{
+				var x = $b.Choose(a)$;
+			}
+			
+			public static T Choose<T>(this T a, T b) { }
+		}
+";
+			var rr = Resolve<CSharpInvocationResolveResult>(program);
+			Assert.AreEqual("A", rr.Type.ReflectionName);
+		}
+		
+		[Test]
+		public void PartiallySpecializedMethod()
+		{
+			string program = @"using System.Collections.Generic;
+		using System.Linq;
+		
+		public class A { }
+		public class B : A { }
+		
+		static class Program
+		{
+			static void Main(A a, B b)
+			{
+				var x = $b.Choose$(a);
+			}
+			
+			public static T Choose<T>(this T a, T b) { }
+		}
+";
+			var rr = Resolve<MethodGroupResolveResult>(program);
+			Assert.IsFalse(rr.Methods.Any());
+			// We deliberately do not specialize the method unless partial specialization is requested explicitly.
+			// This is because the actual type (when considering the whole invocation, not just the method group)
+			// is actually A.
+			Assert.AreEqual("``0", rr.GetExtensionMethods().Single().Single().ReturnType.ReflectionName);
+			Assert.AreEqual("``0", rr.GetEligibleExtensionMethods(false).Single().Single().ReturnType.ReflectionName);
+			Assert.AreEqual("B", rr.GetEligibleExtensionMethods(true).Single().Single().ReturnType.ReflectionName);
+		}
 	}
 }

ICSharpCode.NRefactory.Tests/CSharp/Resolver/LocalTypeInferenceTests.cs

@@ -210,35 +210,5 @@ static class ExtMethods {
 			var rr = Resolve<TypeResolveResult>(program);
 			Assert.AreEqual("System.Int32", rr.Type.ReflectionName);
 		}
-
-		[Test]
-		public void InfertypeFromOverwrittenMethodArguments()
-		{
-			string program = @"using System.Collections.Generic;
-		using System.Linq;
-		
-		public class A
-		{
-		}
-		
-		public class B : A
-		{
-		}
-		
-		class Program
-		{
-			static void Main(string[] args)
-			{
-				IEnumerable<B> list = new List<B>();
-				var arr = list.ToArray<A>();
-				$arr$.ToString();
-			}
-		}
-";
-			var lrr = Resolve<LocalResolveResult>(program);
-			Assert.AreEqual("A[]", lrr.Type.FullName);
-		}
-
-
 	}
 }