[4.1.x] Fixed #33905 -- Fixed CheckConstraint() validation on range fields.

Bug in 667105877e.

Backport of e0ae1363ec from main

django/contrib/postgres/fields/ranges.py

@@ -78,6 +78,9 @@ class RangeField(models.Field):
     def _choices_is_value(cls, value):
         return isinstance(value, (list, tuple)) or super()._choices_is_value(value)
 
+    def get_placeholder(self, value, compiler, connection):
+        return "%s::{}".format(self.db_type(connection))
+
     def get_prep_value(self, value):
         if value is None:
             return None

docs/releases/4.1.1.txt

@@ -32,3 +32,6 @@ Bugfixes
 
 * Fixed a bug in Django 4.1 that caused a crash of model validation on
   ``UniqueConstraint()`` with field names in ``expressions`` (:ticket:`33902`).
+
+* Fixed a bug in Django 4.1 that caused an incorrect validation of
+  ``CheckConstraint()`` with range fields on PostgreSQL (:ticket:`33905`).

tests/postgres_tests/test_constraints.py

@@ -113,6 +113,41 @@ class SchemaTests(PostgreSQLTestCase):
             timestamps_inner=(datetime_1, datetime_2),
         )
 
+    def test_check_constraint_range_contains(self):
+        constraint = CheckConstraint(
+            check=Q(ints__contains=(1, 5)),
+            name="ints_contains",
+        )
+        msg = f"Constraint “{constraint.name}” is violated."
+        with self.assertRaisesMessage(ValidationError, msg):
+            constraint.validate(RangesModel, RangesModel(ints=(6, 10)))
+
+    def test_check_constraint_range_lower_upper(self):
+        constraint = CheckConstraint(
+            check=Q(ints__startswith__gte=0) & Q(ints__endswith__lte=99),
+            name="ints_range_lower_upper",
+        )
+        msg = f"Constraint “{constraint.name}” is violated."
+        with self.assertRaisesMessage(ValidationError, msg):
+            constraint.validate(RangesModel, RangesModel(ints=(-1, 20)))
+        with self.assertRaisesMessage(ValidationError, msg):
+            constraint.validate(RangesModel, RangesModel(ints=(0, 100)))
+        constraint.validate(RangesModel, RangesModel(ints=(0, 99)))
+
+    def test_check_constraint_range_lower_with_nulls(self):
+        constraint = CheckConstraint(
+            check=Q(ints__isnull=True) | Q(ints__startswith__gte=0),
+            name="ints_optional_positive_range",
+        )
+        constraint.validate(RangesModel, RangesModel())
+        constraint = CheckConstraint(
+            check=Q(ints__startswith__gte=0),
+            name="ints_positive_range",
+        )
+        msg = f"Constraint “{constraint.name}” is violated."
+        with self.assertRaisesMessage(ValidationError, msg):
+            constraint.validate(RangesModel, RangesModel())
+
     def test_opclass(self):
         constraint = UniqueConstraint(
             name="test_opclass",