Use correct proxy type in InterfaceProxy

CHANGELOG.md

@@ -9,6 +9,7 @@ The format is loosely based on [Keep a Changelog](http://keepachangelog.com/en/1
 #### Fixed
 
 * AmbiguousMatchException when setting up the property, that hides another one (@ishatalkin, #939)
+* `ArgumentException` ("Interface not found") when setting up `object.ToString` on an interface mock (@vslynko, #942)
 
 ## 4.13.0 (2019-08-31)
 

src/Moq/ProxyFactories/InterfaceProxy.cs

@@ -27,7 +27,7 @@ public sealed override bool Equals(object obj)
 		{
 			// Forward this call to the interceptor, so that `object.Equals` can be set up.
 			var interceptor = (IInterceptor)((IProxy)this).Interceptor;
-			var invocation = new Invocation(interceptor.GetType(), equalsMethod, obj);
+			var invocation = new Invocation(this.GetType(), equalsMethod, obj);
 			interceptor.Intercept(invocation);
 			return (bool)invocation.ReturnValue;
 		}
@@ -38,7 +38,7 @@ public sealed override int GetHashCode()
 		{
 			// Forward this call to the interceptor, so that `object.GetHashCode` can be set up.
 			var interceptor = (IInterceptor)((IProxy)this).Interceptor;
-			var invocation = new Invocation(interceptor.GetType(), getHashCodeMethod);
+			var invocation = new Invocation(this.GetType(), getHashCodeMethod);
 			interceptor.Intercept(invocation);
 			return (int)invocation.ReturnValue;
 		}
@@ -49,7 +49,7 @@ public sealed override string ToString()
 		{
 			// Forward this call to the interceptor, so that `object.ToString` can be set up.
 			var interceptor = (IInterceptor)((IProxy)this).Interceptor;
-			var invocation = new Invocation(interceptor.GetType(), toStringMethod);
+			var invocation = new Invocation(this.GetType(), toStringMethod);
 			interceptor.Intercept(invocation);
 			return (string)invocation.ReturnValue;
 		}

tests/Moq.Tests/Regressions/IssueReportsFixture.cs

@@ -3150,6 +3150,57 @@ private void SetupIntMethod(Action callback)
 
 		#endregion
 
+		#region 942
+
+		public class Issue942
+		{
+			public interface IContent
+			{
+				string Name { get; set; }
+			}
+
+			public interface IContainer
+			{
+				IContent Content { get; set; }
+			}
+
+			private const string toStringReturnValue = "some string here";
+
+			[Fact]
+			public void Setup_ToString_before_Name()
+			{
+				this.TestImpl(contentMock =>
+				{
+					contentMock.Setup(c => c.ToString()).Returns(toStringReturnValue);
+					contentMock.Setup(c => c.Name);
+				});
+			}
+
+			[Fact]
+			public void Setup_ToString_after_Name()
+			{
+				this.TestImpl(contentMock =>
+				{
+					contentMock.Setup(c => c.Name);
+					contentMock.Setup(c => c.ToString()).Returns(toStringReturnValue);
+				});
+			}
+
+			private void TestImpl(Action<Mock<IContent>> setup)
+			{
+				var contentMock = new Mock<IContent>();
+				var containerMock = new Mock<IContainer>();
+
+				containerMock.Setup(c => c.Content).Returns(contentMock.Object);
+				setup(contentMock);
+
+				Assert.Equal(toStringReturnValue, contentMock.Object.ToString());
+				Assert.Equal(toStringReturnValue, containerMock.Object.Content.ToString());
+			}
+		}
+
+		#endregion
+
 		// Old @ Google Code
 
 		#region #47