Type cast with impossible types

Reports calls to `typing.cast` where no possible value of the source type can be assignable to the target type. We can refer to this as "non overlapping" types

This usually indicates a mistake. If the conversion is intentional, first convert the expression to the common parent type to make the intent explicit.

Example:

from typing import cast

# Non-overlapping types — likely a mistake
cast(int, "a")          # 'str' -> 'int'
cast(list[int], ["a"])  # 'list[str]' -> 'list[int]'

# Recommended explicit escape hatch is to use a "double cast"
cast(int, cast(object, "a"))  # ok

# Legitimate overlapping cases
cast(int, object())    # a valid down cast
cast(object, 1)        # a valid up cast

# While the following is an invalid cast, as list is invariant. It's not currently supported by this inspection
int_list = [1, 2, 3]
cast(list[object], int_list)

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

PyInvalidCast

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | Python

The inspection relies on static type information; when a type is unknown, no warning is reported. Variance of generic types is not yet considered.

Inspection ID: PyInvalidCastInspection

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

//noinspection PyInvalidCast

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

Inspection Details
By default bundled with:	CLion 2025.2, DataSpell 2025.2, PyCharm 2025.2,
Can be installed with plugin:	Python Community Edition, 252.26661.0

Last modified: 18 September 2025