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%% Dialyzer couldn't infer that monitor_diskspace would go in an infinite loop
%% instead of crashing due to the existence of list comprehensions that have a
%% normal success typing. These were added to the monitor_diskspace's SCC and
%% dialyzer_typesig didn't try to assign unit() to monitor_diskspace, as it
%% required all the members of the SCC to return none().
%%
%% Testcase was submitted in erlang-questions mailing list by Prashanth Mundkur
%% (http://erlang.org/pipermail/erlang-questions/2011-May/058063.html)
-module(no_return_bug).
-export([diskspace/1, monitor_diskspace/2, refresh_tags/1, monitor_launch/0]).
-type diskinfo() :: {non_neg_integer(), non_neg_integer()}.
-spec diskspace(nonempty_string()) -> {'ok', diskinfo()} | {'error', term()}.
diskspace(Path) ->
case Path of
"a" -> {ok, {0,0}};
_ -> {error, error}
end.
-spec monitor_diskspace(nonempty_string(),
[{diskinfo(), nonempty_string()}]) ->
no_return().
monitor_diskspace(Root, Vols) ->
Df = fun(VolName) ->
diskspace(filename:join([Root, VolName]))
end,
NewVols = [{Space, VolName}
|| {VolName, {ok, Space}}
<- [{VolName, Df(VolName)}
|| {_OldSpace, VolName} <- Vols]],
monitor_diskspace(Root, NewVols).
-spec refresh_tags(nonempty_string()) -> no_return().
refresh_tags(Root) ->
{ok, _} = diskspace(Root),
refresh_tags(Root).
monitor_launch() ->
spawn_link(fun() -> refresh_tags("abc") end),
spawn_link(fun() -> monitor_diskspace("root", [{{0,0}, "a"}]) end).
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