fix #1188

src/Moq/Protected/ProtectedMock.cs

@@ -512,12 +512,12 @@ private static Type[] ToArgTypes(object[] args)
 
 		private static Expression ToExpressionArg(Type type, object arg)
 		{
-			if (arg is LambdaExpression lambda)
+			if (arg is LambdaExpression lambda && !typeof(LambdaExpression).IsAssignableFrom(type))
 			{
 				return lambda.Body;
 			}
 
-			if (arg is Expression expression)
+			if (arg is Expression expression && !typeof(Expression).IsAssignableFrom(type))
 			{
 				return expression;
 			}

tests/Moq.Tests/ProtectedMockFixture.cs

@@ -2,7 +2,7 @@
 // All rights reserved. Licensed under the BSD 3-Clause License; see License.txt.
 
 using System;
-
+using System.Linq.Expressions;
 using Moq.Protected;
 
 using Xunit;
@@ -855,6 +855,17 @@ public void DoesNotThrowIfVerifySetPropertyTimesReached()
 			mock.Protected().VerifySet<string>("ProtectedValue", Times.Exactly(2), ItExpr.IsAny<string>());
 		}
 
+		[Fact]
+		public void SetupShouldWorkWithExpressionTypes()
+		{
+			var mock = new Mock<FooBase>();
+			var expression = Expression.Constant(1);
+			Expression setExpression = null;
+			mock.Protected().SetupSet<Expression>("ExpressionProperty", expression).Callback(expr => setExpression = expr);
+			mock.Object.SetExpressionProperty(expression);
+			Assert.Equal(expression, setExpression);
+		}
+
 		public class MethodOverloads
 		{
 			public void ExecuteDo(int a, int b)
@@ -952,6 +963,12 @@ protected virtual FooBase Overloaded(MyDerived myBase)
 
 		public class FooBase
 		{
+			protected virtual ConstantExpression ExpressionProperty { get; set; }
+			public void SetExpressionProperty(ConstantExpression expression)
+			{
+				ExpressionProperty = expression;
+			}
+
 			public virtual string PublicValue { get; set; }
 
 			protected internal virtual string ProtectedInternalValue { get; set; }