Extend parser to allow specification of RULES that never fire. #7162

compiler/parser/Parser.y.pp

@@ -882,6 +882,7 @@ activation :: { Maybe Activation }
 explicit_activation :: { Activation }  -- In brackets
         : '[' INTEGER ']'               { ActiveAfter  (fromInteger (getINTEGER $2)) }
         | '[' '~' INTEGER ']'           { ActiveBefore (fromInteger (getINTEGER $3)) }
+	| '[' '~' ']'                   { NeverActive }
 
 rule_forall :: { [RuleBndr RdrName] }
         : 'forall' rule_var_list '.'            { $2 }