Expert.DependencySourceA t represents the edge from a child incremental to a parent expert node. A t is stateful, you cannot use the same t to link one child node to multiple parents at the same time.
val sexp_of_t :
('a -> Sexplib0.Sexp.t) ->
('w -> Sexplib0.Sexp.t) ->
('a, 'w) t ->
Sexplib0.Sexp.tWhen calling create ?on_change child, nothing happens until the t is linked to a parent. see Node.add_dependency for documentation of on_change.