Assertions - Temporal LHS error in throughout operator

In reply to shivamdec:
******* PLEASE SEE MY CORRECTIONS BELOW THIS POST ********
I see the issue here.
1800’2012 says that a sequence is

 
expression_or_dist throughout sequence_expr
// and it is NOT the following 
sequence  throughout sequence_expr // ILLEGAL !!!! 
What we have is 
##1 ($stable(gray_count) || gray_count === "X")  // a sequence 
throughout (iso_input[->1]) // thus it is illegal 
My tool is in error. 
************** NOTE *************
[Ben] Errata: My tool is not in error, see my last post below

The fix:

  
ap_gray_cnt_value_chk: assert property(
	@(posedge clk ) (start_addr == 'h10 && iso_input) |-> 
	##1 
        (  // expression_or_dist throughout sequence_expr
         ($stable(gray_count) || gray_count === "X") throughout 
         (iso_input[->1])
         )
       );
// ANOTHER FIX 
ap_gray_cnt_value_chk: assert property(
		@(posedge clk ) (start_addr == 'h10 && iso_input) |=> 
		($stable(gray_count) || gray_count === "X") throughout 
                 (iso_input[->1])
     );

Ben Cohen
http://www.systemverilog.us/ ben@systemverilog.us
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