anchor.diff:  make_tree(list_comp, [[T], B]) -> list_comp(T, B);
   make_tree(macro, [[N]]) -> macro(N);
   make_tree(macro, [[N], A]) -> macro(N, A);
  +make_tree(map_expr, [Fs]) -> map_expr(Fs);
  +make_tree(map_expr, [[E], Fs]) -> map_expr(E, Fs);
  +make_tree(map_field_assoc, [[K], [V]]) -> map_field_assoc(K, V);
  +make_tree(map_field_exact, [[K], [V]]) -> map_field_exact(K, V);
   make_tree(match_expr, [[P], [E]]) -> match_expr(P, E);
   make_tree(named_fun_expr, [[N], C]) -> named_fun_expr(N, C);
   make_tree(module_qualifier, [[M], [N]]) -> module_qualifier(M, N);
  
positive.code: 		     try_expr_clauses(T),
  		     try_expr_handlers(T),
  		     try_expr_after(T)];
  	        map ->
  		    [map_elements(T)];
  		map_field_assoc ->
  		    [map_field_elements(T)];
  		map_field_exact ->
  		    [map_field_elements(T)];
  		tuple ->
  		    [tuple_elements(T)]
  	    end
  
negative.code: make_tree(rule, [[N], C]) -> rule(N, C);
  make_tree(size_qualifier, [[N], [A]]) -> size_qualifier(N, A);
  make_tree(try_expr, [B, C, H, A]) -> try_expr(B, C, H, A);
  make_tree(tuple, [E]) -> tuple(E).
  
  
  %% =====================================================================
  