dialyzerのエラーサンプル集 その1 #Erlang

現在編集中です。

ソースコード

error_sample.erl

-module(error_sample).

%%----------------------------------------------------------------------------------------------------------------------
%% Exported API
%%----------------------------------------------------------------------------------------------------------------------
-export([
         h/1
        ]).

%%----------------------------------------------------------------------------------------------------------------------
%% Macros & Records & Types
%%----------------------------------------------------------------------------------------------------------------------
-record(r, {
             item :: term()
           }).
-record(s, {
             item1 :: term(),
             item2 :: term()
           }).

-type r_list() :: [#r{}].
-type s_list() :: [#s{}].

%%----------------------------------------------------------------------------------------------------------------------
%% Exported Functions
%%----------------------------------------------------------------------------------------------------------------------
-spec h([term()]) -> ok.
h(List) ->
    {_, F} = f(List),
    g(F).

%%----------------------------------------------------------------------------------------------------------------------
%% Internal Function
%%----------------------------------------------------------------------------------------------------------------------
-spec f([term()]) -> {[1], r_list()}. % XXX: r_list() がおかしい
f(List) ->
    f(List, {[], []}).

-spec f([term()], {[1], s_list()}) -> {[1], s_list()}.
f([], R) ->
    R;
f([H|T], {R1, R2}) ->
    f(T, {[1|R1], [#s{item1=H}|R2]}).

-spec g(s_list()) -> ok.
g([]) ->
    ok;
g([H|T]) -> % error_sample.erl:xx: The pattern [H | T] can never match the type []
    io:format("~p", [H#s.item1]),
    g(T).

エラー

$ dialyzer ...
error_sample.erl:xx: The pattern [H | T] can never match the type []