From 36e266f560d51a4bd2d7c00913d8ece91b41f255 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Sitko?= <mic.sitko@gmail.com>
Date: Wed, 21 Dec 2016 22:35:52 +0100
Subject: [PATCH] resolve generics constrained with generic parameters

---
 src/Autofac/Util/TypeExtensions.cs            |  7 +++++++
 .../OpenGenerics/ComplexGenericsTests.cs      | 19 ++++++++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/Autofac/Util/TypeExtensions.cs b/src/Autofac/Util/TypeExtensions.cs
index 4c4195903..6a1b4b57b 100644
--- a/src/Autofac/Util/TypeExtensions.cs
+++ b/src/Autofac/Util/TypeExtensions.cs
@@ -74,6 +74,7 @@ public static bool IsCompatibleWithGenericParameterConstraints(this Type generic
                 var parameterTypeInfo = parameter.GetTypeInfo();
 
                 if (argumentDefinitionTypeInfo.GetGenericParameterConstraints()
+                    .Select(constraint => SubstituteGenericParameterConstraint(parameters, constraint))
                     .Any(constraint => !ParameterCompatibleWithTypeConstraint(parameter, constraint)))
                 {
                     return false;
@@ -160,6 +161,12 @@ private static IEnumerable<Type> FindAssignableTypesThatClose(Type candidateType
                 .Where(t => t.IsClosedTypeOf(openGenericServiceType));
         }
 
+        private static Type SubstituteGenericParameterConstraint(Type[] parameters, Type constraint)
+        {
+            if (!constraint.IsGenericParameter) return constraint;
+            return parameters[constraint.GenericParameterPosition];
+        }
+
         private static bool ParameterCompatibleWithTypeConstraint(Type parameter, Type constraint)
         {
             return constraint.GetTypeInfo().IsAssignableFrom(parameter.GetTypeInfo()) ||
diff --git a/test/Autofac.Test/Features/OpenGenerics/ComplexGenericsTests.cs b/test/Autofac.Test/Features/OpenGenerics/ComplexGenericsTests.cs
index 0cafbf18b..7509a6bc7 100644
--- a/test/Autofac.Test/Features/OpenGenerics/ComplexGenericsTests.cs
+++ b/test/Autofac.Test/Features/OpenGenerics/ComplexGenericsTests.cs
@@ -220,10 +220,27 @@ public void CanResolveComponentWhenConstraintsAreNested()
             builder.RegisterGeneric(typeof(MultiConstrained<,>));
 
             var container = builder.Build();
-
+            
             Assert.True(container.IsRegistered<MultiConstrained<int, IConstrainedConstraintWithOnlyAddedArgument<string>>>());
         }
 
+        public class ConstrainedWithGenericParameter<T1, T2>
+            where T1 : T2
+        {
+        }
+
+        [Fact]
+        public void CanResolveComponentWhenGenericParameterIsConstrainedWithOtherGenericParameter()
+        {
+            var builder = new ContainerBuilder();
+
+            builder.RegisterGeneric(typeof(ConstrainedWithGenericParameter<,>));
+
+            var container = builder.Build();
+
+            Assert.True(container.IsRegistered<ConstrainedWithGenericParameter<int, object>>());
+        }
+
         [Fact(Skip = "Issue #688")]
         public void GenericArgumentArityDifference()
         {