# In Operator on Unsupported Objects
# Detects 'in' and 'not in' used on objects that don't support containment
id: in-operator-unsupported
name: In and Not In Operators Should Be Used on Valid Objects
severity: warning
category: reliability
defect_class: correctness
inline_tier: warning
language: python

message: "'in' operator used on object that may not support containment"

description: |
  The 'in' and 'not in' operators require objects implementing __contains__,
  __iter__, or __getitem__. Using them on incompatible types causes TypeError.

  ✅ FIX: Check object type or use appropriate method

  ```python
  if isinstance(obj, (list, dict, set, str)) and x in obj:
      pass
  ```

query: |
  (comparison_operator
    (identifier) @OBJ
    "in"
    (identifier) @TARGET)
  (comparison_operator
    (identifier) @OBJ
    "not"
    "in"
    (identifier) @TARGET)

metavars:
  - OBJ
  - TARGET

post_filter: check_in_operator_types

tags:
  - reliability
  - python
  - type-error

examples:
  bad: |
    x = 5
    if x in None:  # BAD - None doesn't support 'in'
        pass

  good: |
    items = [1, 2, 3]
    if x in items:  # GOOD - list supports 'in'
        pass

has_fix: false