Use base type for generic argument matching

.vscode/tasks.json

@@ -3,6 +3,7 @@
     {
       "args": [
         "build",
+        "${workspaceFolder}/Autofac.sln",
         "/property:GenerateFullPaths=true",
         "/consoleloggerparameters:NoSummary"
       ],
@@ -17,6 +18,24 @@
       },
       "problemMatcher": "$msCompile",
       "type": "shell"
+    },
+    {
+      "args": [
+        "test",
+        "${workspaceFolder}/Autofac.sln",
+        "/property:GenerateFullPaths=true",
+        "/consoleloggerparameters:NoSummary",
+        "--filter",
+        "FullyQualifiedName!~Benchmark"
+      ],
+      "command": "dotnet",
+      "group": {
+        "isDefault": true,
+        "kind": "test"
+      },
+      "label": "test",
+      "problemMatcher": "$msCompile",
+      "type": "process"
     }
   ],
   "version": "2.0.0"

src/Autofac/Features/OpenGenerics/OpenGenericServiceBinder.cs

@@ -173,7 +173,44 @@ public static bool TryBindOpenGenericDelegateService(
 
         if (!serviceType.IsInterface)
         {
-            return TryFindServiceArgumentsForImplementation(implementationType, serviceGenericArguments, serviceTypeDefinition.GetGenericArguments());
+            /* Issue #1315: We walk backwards in the inheritance hierarchy to
+             * find the open generic because that's the only way to ensure the
+             * generic argument names match.
+             *
+             * If you have a class BaseClass<T1, T2> and a derived class
+             * DerivedClass<A1, A2> : BaseClass<A2, A1> then then arguments need
+             * to line up name-wise like...
+             * A2 -> T1
+             * A1 -> T2
+             *
+             * Having those symbols aligned means that, later, we can do a
+             * name-based match to populate the generic arguments.
+             *
+             * If you do a typeof(BaseClass<,>) then the generic arguments are
+             * named T1 and T2, which doesn't help us line up the arguments in
+             * the derived class because the names and order have changed.
+             * However, if you start at the derived class and walk backwards up
+             * the inheritance hierarchy then instead of getting the original
+             * T1/T2 naming, we get the names A1/A2 - the symbols as lined up by
+             * the compiler.
+             *
+             * This is the same reason why Type.GetInterfaces() "just works" -
+             * it's the generic in relation to the derived/implementing type
+             * rather than just typeof(MyInterface<,>), so the names all line
+             * up.
+             */
+            var baseType = GetGenericBaseType(implementationType, serviceTypeDefinition);
+            if (baseType == null)
+            {
+                // If it's not an interface, the implementation type MUST have derived from
+                // the generic service type at some point or there's no way to cast.
+                return Array.Empty<Type>();
+            }
+
+            return TryFindServiceArgumentsForImplementation(
+                    implementationType,
+                    serviceGenericArguments,
+                    baseType.GenericTypeArguments);
         }
 
         var availableArguments = GetInterfaces(implementationType, serviceType)
@@ -199,6 +236,22 @@ public static bool TryBindOpenGenericDelegateService(
             .ToArray();
     }
 
+    private static Type? GetGenericBaseType(Type implementationType, Type serviceTypeDefinition)
+    {
+        var baseType = implementationType.BaseType;
+        while (baseType != null)
+        {
+            if (baseType.IsGenericType && baseType.GetGenericTypeDefinition() == serviceTypeDefinition)
+            {
+                break;
+            }
+
+            baseType = baseType.BaseType;
+        }
+
+        return baseType;
+    }
+
     private static Type[] GetInterfaces(Type implementationType, Type serviceType) =>
         implementationType.GetInterfaces()
             .Where(i => i.Name == serviceType.Name && i.Namespace == serviceType.Namespace)

test/Autofac.Specification.Test/Registration/OpenGenericTests.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Autofac Project. All rights reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-using Autofac.Test.Scenarios.Graph1.GenericContraints;
+using Autofac.Test.Scenarios.Graph1.GenericConstraints;
 
 namespace Autofac.Specification.Test.Registration;
 
@@ -42,7 +42,47 @@ public void ResolveWithMultipleCandidatesLimitedByGenericConstraintsShouldSuccee
         Assert.NotNull(resolved);
     }
 
+    // Issue #1315: Class services fail to resolve if the names on the type
+    // arguments are changed.
+    [Fact]
+    public void ResolveClassWithRenamedTypeArguments()
+    {
+        var containerBuilder = new ContainerBuilder();
+        containerBuilder.RegisterGeneric(typeof(DerivedRepository<,>)).As(typeof(BaseRepository<,>));
+
+        var container = containerBuilder.Build();
+        var resolved = container.Resolve<BaseRepository<string, int>>();
+        Assert.IsType<DerivedRepository<int, string>>(resolved);
+    }
+
+    // Issue #1315: Class services fail to resolve if the names on the type
+    // arguments are changed. We should be able to handle a deep inheritance chain.
+    [Fact]
+    public void ResolveClassTwoLevelsDownWithRenamedTypeArguments()
+    {
+        var containerBuilder = new ContainerBuilder();
+        containerBuilder.RegisterGeneric(typeof(TwoLevelsDerivedRepository<,>)).As(typeof(BaseRepository<,>));
+
+        var container = containerBuilder.Build();
+        var resolved = container.Resolve<BaseRepository<string, int>>();
+        Assert.IsType<TwoLevelsDerivedRepository<int, string>>(resolved);
+    }
+
     private class SelfComponent<T> : IImplementedInterface<T>
     {
     }
+
+    private class BaseRepository<T1, T2>
+    {
+    }
+
+    // Issue #1315: Class services fail to resolve if the names on the type
+    // arguments are changed.
+    private class DerivedRepository<TSecond, TFirst> : BaseRepository<TFirst, TSecond>
+    {
+    }
+
+    private class TwoLevelsDerivedRepository<TA, TB> : DerivedRepository<TA, TB>
+    {
+    }
 }

test/Autofac.Specification.Test/Resolution/Graph1/GenericContraints/A.cs → test/Autofac.Specification.Test/Resolution/Graph1/GenericConstraints/A.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Autofac Project. All rights reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-namespace Autofac.Test.Scenarios.Graph1.GenericContraints;
+namespace Autofac.Test.Scenarios.Graph1.GenericConstraints;
 
 public class A : IA
 {

test/Autofac.Specification.Test/Resolution/Graph1/GenericContraints/ClassWithParameterlessButNotPublicConstructor.cs → test/Autofac.Specification.Test/Resolution/Graph1/GenericConstraints/ClassWithParameterlessButNotPublicConstructor.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Autofac Project. All rights reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-namespace Autofac.Test.Scenarios.Graph1.GenericContraints;
+namespace Autofac.Test.Scenarios.Graph1.GenericConstraints;
 
 public class ClassWithParameterlessButNotPublicConstructor
 {

test/Autofac.Specification.Test/Resolution/Graph1/GenericContraints/IA.cs → test/Autofac.Specification.Test/Resolution/Graph1/GenericConstraints/IA.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Autofac Project. All rights reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-namespace Autofac.Test.Scenarios.Graph1.GenericContraints;
+namespace Autofac.Test.Scenarios.Graph1.GenericConstraints;
 
 public interface IA
 {

test/Autofac.Specification.Test/Resolution/Graph1/GenericContraints/IB.cs → test/Autofac.Specification.Test/Resolution/Graph1/GenericConstraints/IB.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Autofac Project. All rights reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-namespace Autofac.Test.Scenarios.Graph1.GenericContraints;
+namespace Autofac.Test.Scenarios.Graph1.GenericConstraints;
 
 public interface IB<TResult>
 {

test/Autofac.Specification.Test/Resolution/Graph1/GenericContraints/Required.cs → test/Autofac.Specification.Test/Resolution/Graph1/GenericConstraints/Required.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Autofac Project. All rights reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-namespace Autofac.Test.Scenarios.Graph1.GenericContraints;
+namespace Autofac.Test.Scenarios.Graph1.GenericConstraints;
 
 public class Required : IB<ClassWithParameterlessButNotPublicConstructor>
 {

test/Autofac.Specification.Test/Resolution/Graph1/GenericContraints/Unrelated.cs → test/Autofac.Specification.Test/Resolution/Graph1/GenericConstraints/Unrelated.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Autofac Project. All rights reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-namespace Autofac.Test.Scenarios.Graph1.GenericContraints;
+namespace Autofac.Test.Scenarios.Graph1.GenericConstraints;
 
 public class Unrelated<T> : IB<T>
     where T : class, new()