dynamic transact-sql contingency table implementing http://stackoverflow.com/a/10404455 in a generic manner

gistfile1.sql

create procedure dbo.dynamic_simple_contingency_table_query
  @withExpression nvarchar(max) -- ^ optional with CTE expression
  , @selectStatement nvarchar(max) -- ^ select statement, should return at least three columns, whose name matches following parameters
  , @row_column_key nvarchar(max) -- ^ column name which identifies row keys (result will have as many distinct rows as found here)
  , @column_column_key nvarchar(max) -- ^ column name which identifies column keys (result will have as many distinct values as found here)
  , @fact_column_key nvarchar(max) -- ^ column name which contains facts
as
begin
declare @sql nvarchar(max)
set @sql = @withExpression 
+'
select z.* into #temptable from ((' + @selectStatement +')) z

declare @cols as nvarchar(max)
declare @query as nvarchar(max)

set @cols = stuff(
	(select distinct '','' + quotename(c.' + @column_column_key + ') from #temptable c for xml path(''''), type).value(''.'', ''nvarchar(max)'')
	, 1
	, 1
	, ''''
)

set @query = 
  ''
select
	' + @row_column_key + '
	, '' + @cols + ''
from
	(
		select
			' + @row_column_key + ' 
			, ' + @fact_column_key + '
			, ' + @column_column_key + '
		from
			#temptable
	) x
	pivot 
	(
		max(' + @fact_column_key + ')
		for ' + @column_column_key + ' in ('' + @cols + '')
	) p
''

execute(@query)
'
execute (@sql)
end

I'm trying to use this on a SQL 2012 table. I get no output from the SP. I believe the problem may be in here:
pivot
(
max(' + @fact_column_key + ')
for ' + @column_column_key + ' in ('' + @cols + '')
) p

I need to return absolute/distinct values in the fact column, not aggregates. I tried:
pivot
(
@fact_column_key
for ' + @column_column_key + ' in ('' + @cols + '')
) p

but that doesn't work. I inserted "print @cols" and "print @query" into the SP to see if it would show me what was being calculated but I get no output.

Any thoughts?