current_value in attribute form relational widget filter don't work with IN operator #66313

What is the bug or the crash?

The feature form has two combo-boxes, each one configured with a key-value table relational widget.

The second combo-box choices should be filtered according to the first combo-box current value.

Steps to reproduce the issue

1. Open the test project inside the GPKG
2. Add a feature in the table my_features with the attribute form
3. See that whatever is selected in the id_a combo-box, the id_b combo-box choices do not change

Go in the filter expression of id_b in the form parameters to switch to a workaround expression, and see that the choices in id_b combo-box do change (see context below).

Versions

Tested with QGIS LTR 3.44.11 and QGIS latest 4.0.2

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

No Duplicate of the Issue

• I have verified that there are no existing issues raised related to my problem.

Additional context

Does not work with current_value(): always falling in the else part

if (
	current_value('id_a') in(1, 2),
	"key" in (1, 2),
	"key" in (3)
)

Works with with_variable()

with_variable('my_id_a', current_value('id_a'),
	if (
		@my_id_a in (1, 2),
		"key" in (1, 2),
		"key" in (3)
	)
)

Works with with_variable() even if the variable is not used but we use current_value()!

with_variable('my_id_a', current_value('id_a'),
	if (
		current_value('id_a') in (1, 2),
		"key" in (1, 2),
		"key" in (3)
	)
)

Works with equality test

if (
	current_value('id_a') = 1 OR current_value('id_a') = 2,
	"key" in (1, 2),
	"key" in (3)
)