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authorZandra Hird <[email protected]>2015-05-08 13:31:57 +0200
committerZandra Hird <[email protected]>2015-05-08 13:31:57 +0200
commitb9c2f04a51ee20e49b74dcdb160ca102a217edc5 (patch)
tree42228dd3233c30246bbc8fec363fd4f8ed485c3f /lib/dialyzer
parent6b15e5e613c4688c5fbd7bc409a011971b699dc3 (diff)
parent00ff3b3776a62402e7977fd9172a926ad62ea449 (diff)
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Merge branch 'aronisstav/dialyzer-inv-mult'
* aronisstav/dialyzer-inv-mult: Fix a bug related to constraints generated for erlang:'*'/2 OTP-12725
Diffstat (limited to 'lib/dialyzer')
-rw-r--r--lib/dialyzer/src/dialyzer_typesig.erl8
-rw-r--r--lib/dialyzer/test/small_SUITE_data/src/inv_mult.erl15
2 files changed, 19 insertions, 4 deletions
diff --git a/lib/dialyzer/src/dialyzer_typesig.erl b/lib/dialyzer/src/dialyzer_typesig.erl
index 1737bfd3a9..6c14860d7d 100644
--- a/lib/dialyzer/src/dialyzer_typesig.erl
+++ b/lib/dialyzer/src/dialyzer_typesig.erl
@@ -1579,11 +1579,11 @@ get_bif_constr({M, F, A} = _BIF, Dst, Args, _State) ->
eval_inv_arith('+', _Pos, Dst, Arg) ->
bif_return(erlang, '-', 2, [Dst, Arg]);
eval_inv_arith('*', _Pos, Dst, Arg) ->
- case t_number_vals(Arg) of
- [0] -> t_integer();
- _ ->
+ Zero = t_from_term(0),
+ case t_is_none(t_inf(Arg, Zero)) of
+ false -> t_integer();
+ true ->
TmpRet = bif_return(erlang, 'div', 2, [Dst, Arg]),
- Zero = t_from_term(0),
%% If 0 is not part of the result, it cannot be part of the argument.
case t_is_subtype(Zero, Dst) of
false -> t_subtract(TmpRet, Zero);
diff --git a/lib/dialyzer/test/small_SUITE_data/src/inv_mult.erl b/lib/dialyzer/test/small_SUITE_data/src/inv_mult.erl
new file mode 100644
index 0000000000..3413556813
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/inv_mult.erl
@@ -0,0 +1,15 @@
+%% Dialyzer was too constraining when checking the relation between the
+%% arguments and result of a multiplication. We should not constrain an argument
+%% if the other operand *may* be zero.
+%%
+%% Bug found by Kostis Sagonas, fixed by Stavros Aronis
+
+-module(inv_mult).
+-compile(export_all).
+
+main(L) ->
+ N = -1 * length(L),
+ fact(N).
+
+fact(0) -> 1;
+fact(N) -> N * fact(N-1).