transform.erl

Tree = {function,1,foo,1,
          [{clause,1,
                   [{var,1,self}],
                   [],
                   [{op,1,'+',{integer,1,1},{integer,1,2}}]}]}.

% Thanks to N_Ox on #erlang for pointing erl_syntax:abstract out.
{value, Tree, _ } = erl_eval:expr(erl_syntax:revert(erl_syntax:abstract(Tree), [])).