Dear Maintainer,

After cliking on "Run" with a simple project file (which I would like to attach to this report but I just don't know how to), I get the following error output:
global_cardinality_fn:20.20-66:
MiniZinc: type error: no function or predicate with this signature found: `global_cardinality(array[int] of var opt int,array[int] of int,array[int] of var int)'
Cannot use the following functions or predicates with the same identifier:
function array [$Y] of var int : global_cardinality(array [$X] of var $$E: x,array [$Y] of $$E: cover):: promise_total;
    (requires 2 arguments, but 3 given)
function array [$Y] of var int : global_cardinality(array [$X] of var opt $$E: x,array [$Y] of $$E: cover):: promise_total;
    (requires 2 arguments, but 3 given)
predicate global_cardinality(array [int] of var int: x,array [int] of int: cover,array [int] of var int: counts);
    (argument 1 expects type array[int] of var int, but type array[int] of var opt int given)

Whereas, when using the official Linux binary archive (version 2.8.5 - 1315243669) taken from https://www.minizinc.org/downloads/, everything works just fine with the very same project file.

Is it conceivable to update testing/sid package version to a newer one?

As a matter of fact, I also get the following list of warnings, which has actually been automatically cropped:
Warning: included file "sum_pred.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "sort.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "roots.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "regular.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "range.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "partition_set.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "nvalue.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "link_set_to_booleans.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "inverse_set.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "inverse.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "int_set_channel.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "global_cardinality_low_up_closed.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "global_cardinality_low_up.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "global_cardinality_closed.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "global_cardinality.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "distribute.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "disjunctive_strict.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "disjoint.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "diffn.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: included file "cumulative.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_<global>.mzn" instead.
Warning: Further warnings have been suppressed.

All the best.
Olivier

retitle 1073819 flatzinc: mznlib is too old for current minizinc
reassign 1073819 flatzinc
found 1073819 6.2.0-5.1
severity 1073819 important
thanks

The error you are seeing originates from Gecode's Flatzinc
implementation, not Minizinc.  Upstream's Minizinc binary package
bundles their own build of it but it's been years since Gecode's made
a release and the Flatzinc implementation in that is too old to handle
current Minizinc.

Debian has two other Flatzinc implementations available, ortools and
chuffed.  Unfortunately ortools-flatzinc is currently not installable
but chuffed-flatzinc should be good to use.

I've been holding off this in hopes of having Gecode do a release but
I'll try to backport whatever changes flatzinc needs instead.  I'm
reassigning and lowering the severity since other parts of Gecode are
fine.