Query: Subquery comparison to null is translated incorrectly

[shaulbehr]

The following query:

                        thoughts = from t in thoughts
                                   let recentCommentUserId = t.ThoughtComments
                                                              .OrderByDescending(c => c.DateTime)
                                                              .Select(c => (Guid?)c.UserId)
                                                              .FirstOrDefault()
                                   where t.UserId != teacherUser.UserId
                                         && (recentCommentUserId == null || recentCommentUserId != teacherUser.UserId)
                                   select t;

translates to:

exec sp_executesql N'SELECT COUNT(*)
FROM [dbo].[Thought] AS [t]
WHERE ([t].[ClassId] = @__criteria_ClassId_Value_0) AND (([t].[UserId] <> @__teacherUser_UserId_1) AND (((
    SELECT TOP(1) [c].[UserId]
    FROM [dbo].[ThoughtComment] AS [c]
    WHERE [t].[ThoughtId] = [c].[ThoughtId]
    ORDER BY [c].[DateTime] DESC
) = NULL) OR ((
    SELECT TOP(1) [c0].[UserId]
    FROM [dbo].[ThoughtComment] AS [c0]
    WHERE [t].[ThoughtId] = [c0].[ThoughtId]
    ORDER BY [c0].[DateTime] DESC
) <> @__teacherUser_UserId_2)))',N'@__criteria_ClassId_Value_0 uniqueidentifier,@__teacherUser_UserId_1 uniqueidentifier,@__teacherUser_UserId_2 uniqueidentifier',@__criteria_ClassId_Value_0='3B7EC359-E000-45D6-A1ED-08D3C74419A2',@__teacherUser_UserId_1='2D1F3B39-5333-4748-FB49-08D3C74418C2',@__teacherUser_UserId_2='2D1F3B39-5333-4748-FB49-08D3C74418C2'

Notice the comparison "= NULL". That doesn't work. It should be 'IS NULL'

[smitpatel]

This is probably fixed by #7950