Type cast between unrelated types

Reports typing.cast calls where the source and target types are unrelated.

An error is reported when neither the source type is a subtype of the target, nor the target type is a subtype of the source. Such casts often indicate a logical error, as an instance of one type cannot be assumed to be an instance of the other, and typing.cast does not dynamically validate the type.

This check applies even to types that could theoretically have a common descendant. For example, it will flag a cast between two sibling classes Left and Right that both inherit from Top, because there is no direct inheritance relationship between them.

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 2025.3, DataSpell 2025.3, IntelliJ IDEA 2025.3, PyCharm 2025.3, Qodana for JVM 2025.3,

Last modified: 03 December 2025