Parse transform to support -spec and behaviour_info in Erlang

behaviour_parse.erl

-module(behaviour_parse).
-export([parse_transform/2]).
-define(CUTOFF, "2.15"). % R15B

parse_transform(AST, _Opts) ->
    [Vsn] = [X || {kernel,_,X} <- application:which_applications()],
    walk_ast(if Vsn >= ?CUTOFF -> spec;
                Vsn < ?CUTOFF -> func
             end,
             AST).

walk_ast(_, []) ->
    []; 
walk_ast(func, [{attribute, _Ln, callback, _}|T]) ->
    walk_ast(func, T); 
walk_ast(spec, [{attribute, Ln, export, List}|T]) ->
    [{attribute, Ln, export, List -- [{behaviour_info,1},{behavior_info,1}]}
     | walk_ast(spec, T)];
walk_ast(spec, [{function, _Ln, behaviour_info,1,_Clauses}|T]) ->
    walk_ast(spec, T); 
walk_ast(spec, [{function, _Ln, behavior_info,1,_Clauses}|T]) ->
    walk_ast(spec, T); 
walk_ast(Type, [H|T]) ->
    [H|walk_ast(Type, T)].

This will obviously break with versions of the kernel < 2.10, but that should be RB09 and prior, which I figure is fairly rare in the wild.