# Known issues

This page collects known issues that were reported by the users.

## Deadlock detection

Deadlock detection is imprecise. It may report false negatives, see Issue 711.

Affected versions: <= 0.15.x

Planned fix: Issue 712

## Updating records with excess fields

Given a record with a type declaration specifying n fields, if that record is given more than n fields and the specification includes an EXCEPT expression that updates the record, Apalache may be unable to check the specification.

In the following example, the variable m is given the type of a record with 1 field (namely a), but it is then assigned to a record with 2 fields (namely a and foo).

VARIABLE
\* @type: [a: Int];
m

Init == m = [a |-> 0, foo |-> TRUE]

Next ==
\/ m' = m
\/ m' = [m EXCEPT !.a = 0]


Given the current (unsound) typing discipline Apalache uses for records, this specification is not considered incorrectly typed. However, due to the update using EXCEPT in the Next operator, the specification cannot be checked.

Affected versions: <= 0.15.x

Planned fix: Issue 401

### Workaround

Add the foo field to the variable's type signature:

VARIABLE
\* @type: [a: Int, foo: Bool];
m

Init == m = [a |-> 0, foo |-> TRUE]

Next ==
\/ m' = m
\/ m' = [m EXCEPT !.a = 0]