Reporting Services :: Parameter Order Of Precedence

I've run into something that really isn't a problem - I corrected the issue with a CTE solution - but, it did raise a question.

I was developing a report and, when I previewed it, I got an error that a parameter was dependent upon the value of another parameter - no forward dependencies allowed.

But, another parameter that used the exact same SQL code - just different fields - works fine.

So, here's the list of parameters;

CurDate is derived by;
DECLARE @CurDate AS date
SET @CurDate =
(
SELECT MAX(Load_Date)
FROM Census_Rpt_Final
)

The parameter that gives me the problem is PCPName. It is a list of names derived by the following;

SELECT DISTINCT
UPPER(PCP_Name) AS [PCP Name]
FROM
Census_Rpt_Final
WHERE
Load_Date = @CurDate
ORDER BY
[PCP Name];

So, OK, fine, I can understand the error. But, MemberName is derived by;

SELECT DISTINCT
RTRIM(UPPER(Member_LName))
+ ', '
+ RTRIM(UPPER(Member_Fname)) AS [Member Name]
FROM
Census_Rpt_Final
WHERE
Load_Date = @CurDate
ORDER BY
[Member Name];

And, it works fine. No Foward Dependency problem at all.

So, my question becomes one of precedence. I see, in the list of parameters, that PCPName precedes CurDate which precedes MemberName. Is the problem because, when it hits PCPName, CurDate has yet to be defined, but when it hits MemberName, CurDate has been defined?

Is SSRS one-pass compiler or multi-pass? My guess is that it's a one-pass, because of the error I'm getting. As I said, I've corrected the problem using;

WITH Date_of_Most_Recent_Census AS
(
SELECT
MAX(Load_Date) AS [CurDate]

[Code] ....

Removing the parameter reference from the code, but it made me curious as to why one worked and the other didn't.