fix in-test when RHS needs coercion from non-Python type

Cython/Compiler/ExprNodes.py

@@ -8741,7 +8741,9 @@ class CmpNode(object):
                 self.special_bool_cmp_utility_code = UtilityCode.load_cached("PyDictContains", "ObjectHandling.c")
                 self.special_bool_cmp_function = "__Pyx_PyDict_Contains"
                 return True
-            elif self.operand2.type.is_pyobject:
+            else:
+                if not self.operand2.type.is_pyobject:
+                    self.operand2 = self.operand2.coerce_to_pyobject(env)
                 self.special_bool_cmp_utility_code = UtilityCode.load_cached("PySequenceContains", "ObjectHandling.c")
                 self.special_bool_cmp_function = "__Pyx_PySequence_Contains"
                 return True

tests/run/inop.pyx

@@ -349,3 +349,30 @@ def constant_empty_sequence(a):
     False
     """
     return a in ()
+
+def test_error_non_iterable(x):
+    """
+    >>> test_error_non_iterable(1)   # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    TypeError: ...iterable...
+    """
+    return x in 42
+
+def test_error_non_iterable_cascaded(x):
+    """
+    >>> test_error_non_iterable_cascaded(1)   # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    TypeError: ...iterable...
+    """
+    return 1 == x in 42
+
+def test_inop_cascaded(x):
+    """
+    >>> test_inop_cascaded(1)
+    False
+    >>> test_inop_cascaded(2)
+    True
+    >>> test_inop_cascaded(3)
+    False
+    """
+    return 1 != x in [2]