avoid turning MemberAccess expressions of literal types into Constants

Author: csboling

src/AutoMapper.Extensions.ExpressionMapping/XpressionMapperVisitor.cs

@@ -57,6 +57,9 @@ protected override Expression VisitMember(MemberExpression node)
                 var baseExpression = node.GetBaseOfMemberExpression();
                 if (baseExpression?.NodeType == ExpressionType.Constant)
                 {
+                    if (node.Type.IsLiteralType())
+                        return node;
+
                     return this.Visit
                     (
                         Expression.Constant

tests/AutoMapper.Extensions.ExpressionMapping.UnitTests/XpressionMapper.Structs.Tests.cs

@@ -161,9 +161,11 @@ public void Can_map_listeral_child_property_of_local_variable_in_filter()
 
             //Act
             var mappedfilter = mapper.MapExpression<Expression<Func<Garage, bool>>>(filter);
+            var mappedrhs = ((BinaryExpression)mappedfilter.Body).Right;
 
             //Assert
             Assert.NotNull(mappedfilter);
+            Assert.Equal(ExpressionType.MemberAccess, mappedrhs.NodeType);
         }
 
         [Fact]