further steps in implementing sink parameters; refs #7041

compiler/ast.nim

@@ -453,6 +453,8 @@ type
     nfPreventCg # this node should be ignored by the codegen
     nfBlockArg  # this a stmtlist appearing in a call (e.g. a do block)
     nfFromTemplate # a top-level node returned from a template
+    nfPreventDestructor # prevent destructor injectsion for the node
+                        # (but not necessarily its children)
 
   TNodeFlags* = set[TNodeFlag]
   TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: beyond that)