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authorHans Bolinder <[email protected]>2018-08-27 13:14:29 +0200
committerHans Bolinder <[email protected]>2018-08-28 08:27:52 +0200
commitfd9b5ae4193fbab66093c88728c0dbeaa3b57312 (patch)
treefd3f8b46afb4b5745f0f9a02b2498cad7826bedc /lib/dialyzer
parent00401985f1c9227b6e94309ae5526c2ebf341527 (diff)
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dialyzer: Improve handling of complex guards
See also https://bugs.erlang.org/browse/ERL-680. The right associative short circuit expressions 'andalso' and 'orelse' are expanded by the Compiler (see v3_core) into 'case' expressions. If parentheses are used to enforce left associativeness, variables are introduced, and the time needed by Dialyzer increases exponentially. Rather than trying to fix Dialyzer itself, v3_core now rewrites repeated use of 'andalso' ('orelse') into right associative expressions before creating the 'case' expressions.
Diffstat (limited to 'lib/dialyzer')
-rw-r--r--lib/dialyzer/test/small_SUITE_data/results/left_assoc2
-rw-r--r--lib/dialyzer/test/small_SUITE_data/src/left_assoc.erl96
2 files changed, 98 insertions, 0 deletions
diff --git a/lib/dialyzer/test/small_SUITE_data/results/left_assoc b/lib/dialyzer/test/small_SUITE_data/results/left_assoc
new file mode 100644
index 0000000000..58cdad29de
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/results/left_assoc
@@ -0,0 +1,2 @@
+
+left_assoc.erl:93: The variable __@2 can never match since previous clauses completely covered the type binary()
diff --git a/lib/dialyzer/test/small_SUITE_data/src/left_assoc.erl b/lib/dialyzer/test/small_SUITE_data/src/left_assoc.erl
new file mode 100644
index 0000000000..0250e4ab49
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/left_assoc.erl
@@ -0,0 +1,96 @@
+-module(left_assoc).
+
+%% As pointed out in ERL-680, analyzing guards with short circuit
+%% operators becomes very slow as the number of left associations
+%% grows.
+
+-spec from_iso8601('Elixir.String':t(), 'Elixir.Calendar':calendar()) ->
+ {ok, t()} | {error, atom()}.
+
+-export_type([t/0]).
+
+-type t() ::
+ #{'__struct__' := 'Elixir.Date',
+ calendar := 'Elixir.Calendar':calendar(),
+ day := 'Elixir.Calendar':day(),
+ month := 'Elixir.Calendar':month(),
+ year := 'Elixir.Calendar':year()}.
+
+-export([from_iso8601/1,
+ from_iso8601/2]).
+
+from_iso8601(__@1) ->
+ from_iso8601(__@1, 'Elixir.Calendar.ISO').
+
+from_iso8601(<<45/integer,_rest@1/binary>>, _calendar@1) ->
+ case raw_from_iso8601(_rest@1, _calendar@1) of
+ {ok,#{year := _year@1} = _date@1} ->
+ {ok,_date@1#{year := - _year@1}};
+ __@1 ->
+ __@1
+ end;
+from_iso8601(<<_rest@1/binary>>, _calendar@1) ->
+ raw_from_iso8601(_rest@1, _calendar@1).
+
+raw_from_iso8601(_string@1, _calendar@1) ->
+ case _string@1 of
+ <<_y1@1/integer,
+ _y2@1/integer,
+ _y3@1/integer,
+ _y4@1/integer,
+ 45/integer,
+ _m1@1/integer,
+ _m2@1/integer,
+ 45/integer,
+ _d1@1/integer,
+ _d2@1/integer>>
+ when
+ ((((((((((((((_y1@1 >= 48
+ andalso
+ _y1@1 =< 57)
+ andalso
+ _y2@1 >= 48)
+ andalso
+ _y2@1 =< 57)
+ andalso
+ _y3@1 >= 48)
+ andalso
+ _y3@1 =< 57)
+ andalso
+ _y4@1 >= 48)
+ andalso
+ _y4@1 =< 57)
+ andalso
+ _m1@1 >= 48)
+ andalso
+ _m1@1 =< 57)
+ andalso
+ _m2@1 >= 48)
+ andalso
+ _m2@1 =< 57)
+ andalso
+ _d1@1 >= 48)
+ andalso
+ _d1@1 =< 57)
+ andalso
+ _d2@1 >= 48)
+ andalso
+ _d2@1 =< 57 ->
+ {ok,
+ #{year => (_y1@1 - 48) * 1000 + (_y2@1 - 48) * 100
+ +
+ (_y3@1 - 48) * 10
+ +
+ (_y4@1 - 48),
+ month => (_m1@1 - 48) * 10 + (_m2@1 - 48),
+ day => (_d1@1 - 48) * 10 + (_d2@1 - 48),
+ calendar => _calendar@1,
+ '__struct__' => 'Elixir.Date'}};
+ __@1 ->
+ case __@1 of
+ _ ->
+ {error,invalid_format};
+ __@2 ->
+ error({with_clause,__@2})
+ end
+ end.