[erlang-bugs] Compiler/linter bug breaking unused variable warnings
Anthony Ramine
n.oxyde@REDACTED
Fri May 31 00:46:57 CEST 2013
Hello,
Smaller test case reproducing the bug, without KeyList2 nor filter/1:
-8<--
-module(missing_warning).
-export([test_missing_warning/2,
test_with_warning1/2,
test_with_warning2/2
]).
-record(data, {aList, bList}).
test_missing_warning(Data, KeyList) -> %% Data, KeyList never used - no warning.
#data{aList = [Key || Key <- []],
bList = [Key || Key <- []]}.
test_with_warning1(Data, KeyList) -> %% Data, KeyList never used - get warning.
#data{aList = [Key || Key <- []]}. %% Only one LC in the record.
test_with_warning2(Data, KeyList) -> %% Data, KeyList never used - get warning.
{data,
[Key || Key <- []], %% Not in a record.
[Key || Key <- []]}.
-->8-
Regards,
--
Anthony Ramine
Le 29 mai 2013 à 20:02, <Anders.Ramsell@REDACTED> <Anders.Ramsell@REDACTED> a écrit :
>
> When a function creates a record and more than one field is bound to the value of a list comprehension the compiler/linter fails to generate warnings for unused variables in that function. I just tested this on R16B and the problem is still there.
>
> I use the following module to test this:
>
> --8<----------------------------------------------------------
> -module(missing_warning).
>
> -export([test_missing_warning/2,
> test_with_warning1/2,
> test_with_warning2/2
> ]).
>
> -record(data, {aList, bList}).
>
> test_missing_warning(Data, KeyList) -> %% Data never used - no warning.
> KeyList2 = filter(KeyList), %% KeyList2 never used - no warning.
> #data{aList = [Key || Key <- KeyList],
> bList = [Key || Key <- KeyList]}.
>
> test_with_warning1(Data, KeyList) -> %% Data never used - get warning.
> KeyList2 = filter(KeyList), %% KeyList2 never used - get warning.
> #data{aList = [Key || Key <- KeyList]}. %% Only one LC in the record.
>
> test_with_warning2(Data, KeyList) -> %% Data never used - get warning.
> KeyList2 = filter(KeyList), %% KeyList2 never used - get warning.
> {data,
> [Key || Key <- KeyList], %% Not in a record.
> [Key || Key <- KeyList]}.
>
> filter(L) -> L.
> --8<----------------------------------------------------------
>
> In all three test functions the variables Data (in the function head) and KeyList2 (in the function body) are unused.
> Compiling the module should produce six warnings but I only get four.
> You get the same result with other "advanced" calls like
> lists:map(fun(Key) -> Key end, KeyList)
> so it's not limited to list comprehensions.
> If the fields are bound to e.g. the variable KeyList directly the warnings work just fine.
>
> /Anders
>
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