1 files changed, 94 insertions, 0 deletions
diff --git a/pylint/test/functional/unsupported_assignment_operation.py b/pylint/test/functional/unsupported_assignment_operation.py
new file mode 100644
index 0000000..a2e5f87
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+++ b/pylint/test/functional/unsupported_assignment_operation.py
@@ -0,0 +1,94 @@
+"""
+Checks that value used in a subscript support assignments
+(i.e. defines __setitem__ method).
+"""
+# pylint: disable=missing-docstring,pointless-statement,expression-not-assigned,wrong-import-position
+# pylint: disable=too-few-public-methods,import-error,invalid-name,wrong-import-order
+import six
+
+# primitives
+numbers = [1, 2, 3]
+numbers[0] = 42
+
+
+bytearray(b"123")[0] = 42
+dict(a=1, b=2)['a'] = 42
+(1, 2, 3)[0] = 42 # [unsupported-assignment-operation]
+
+# list/dict comprehensions are fine
+[x for x in range(10)][0] = 42
+{x: 10 - x for x in range(10)}[0] = 42
+
+
+# instances
+class NonSubscriptable(object):
+    pass
+
+class Subscriptable(object):
+    def __setitem__(self, key, value):
+        return key + value
+
+NonSubscriptable()[0] = 24  # [unsupported-assignment-operation]
+NonSubscriptable[0] = 24 # [unsupported-assignment-operation]
+Subscriptable()[0] = 24
+Subscriptable[0] = 24 # [unsupported-assignment-operation]
+
+# generators are not subscriptable
+def powers_of_two():
+    k = 0
+    while k < 10:
+        yield 2 ** k
+        k += 1
+
+powers_of_two()[0] = 42 # [unsupported-assignment-operation]
+powers_of_two[0] = 42  # [unsupported-assignment-operation]
+
+
+# check that primitive non subscriptable types are catched
+True[0] = 24  # [unsupported-assignment-operation]
+None[0] = 42 # [unsupported-assignment-operation]
+8.5[0] = 24 # [unsupported-assignment-operation]
+10[0] = 24 # [unsupported-assignment-operation]
+
+# sets are not subscriptable
+{x ** 2 for x in range(10)}[0] = 24 # [unsupported-assignment-operation]
+set(numbers)[0] = 24 # [unsupported-assignment-operation]
+frozenset(numbers)[0] = 42 # [unsupported-assignment-operation]
+
+# skip instances with unknown base classes
+from some_missing_module import LibSubscriptable
+
+class MaybeSubscriptable(LibSubscriptable):
+    pass
+
+MaybeSubscriptable()[0] = 42
+
+# subscriptable classes (through metaclasses)
+
+class MetaSubscriptable(type):
+    def __setitem__(cls, key, value):
+        return key + value
+
+class SubscriptableClass(six.with_metaclass(MetaSubscriptable, object)):
+    pass
+
+SubscriptableClass[0] = 24
+SubscriptableClass()[0] = 24 # [unsupported-assignment-operation]
+
+# functions are not subscriptable
+def test(*args, **kwargs):
+    return args, kwargs
+
+test()[0] = 24 # [unsupported-assignment-operation]
+test[0] = 24 # [unsupported-assignment-operation]
+
+# deque
+from collections import deque
+deq = deque(maxlen=10)
+deq.append(42)
+deq[0] = 42
+
+# tuples assignment
+values = [1, 2, 3, 4]
+(values[0], values[1]) = 3, 4
+(values[0], SubscriptableClass()[0]) = 42, 42 # [unsupported-assignment-operation]