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author | Stavros Aronis <[email protected]> | 2015-04-23 11:15:47 +0200 |
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committer | Zandra Hird <[email protected]> | 2015-05-05 15:27:49 +0200 |
commit | 00ff3b3776a62402e7977fd9172a926ad62ea449 (patch) | |
tree | 2ae704d67146a9aaab7b5702dd083d0762ce804d /lib/dialyzer/test/small_SUITE_data | |
parent | 66260d0606fcbaad3d5179288fea90cfe546cbbe (diff) | |
download | otp-00ff3b3776a62402e7977fd9172a926ad62ea449.tar.gz otp-00ff3b3776a62402e7977fd9172a926ad62ea449.tar.bz2 otp-00ff3b3776a62402e7977fd9172a926ad62ea449.zip |
Fix a bug related to constraints generated for erlang:'*'/2
For Rst = A1 * A2, typesig for erlang:'*'/2 was constraining the
arguments A1 and A2 in the 'reverse' direction by requiring that A2 is a
subtype of Rst div A1, unless A1 is a hard zero. This is not correct: if
for example both Rst and A1 are non_negative, such a constraint will
first force A1 to be non-zero for the division to go through and then
require A2 to be non_negative as non_negative div positive =
non_negative, always (see commited test).
In the fixed version, we are not constraining an argument if the other
operand *may* be zero.
Diffstat (limited to 'lib/dialyzer/test/small_SUITE_data')
-rw-r--r-- | lib/dialyzer/test/small_SUITE_data/src/inv_mult.erl | 15 |
1 files changed, 15 insertions, 0 deletions
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). |