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Binary operations on classes

crates/ty_python_semantic/resources/mdtest/binary/classes.md

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Binary operations on classes

Union of two classes

Unioning two classes via the | operator is only available in Python 3.10 and later.

toml
[environment]
python-version = "3.10"
py
class A: ...
class B: ...

reveal_type(A | B)  # revealed: <types.UnionType special-form 'A | B'>

Union of two classes (prior to 3.10)

toml
[environment]
python-version = "3.9"
py
class A: ...
class B: ...

# error: "Operator `|` is not supported between objects of type `<class 'A'>` and `<class 'B'>`"
reveal_type(A | B)  # revealed: Unknown

Other binary operations resulting in UnionType

toml
[environment]
python-version = "3.12"
py
class A: ...
class B: ...

def _(sub_a: type[A], sub_b: type[B]):
    reveal_type(A | sub_b)  # revealed: <types.UnionType special-form>
    reveal_type(sub_a | B)  # revealed: <types.UnionType special-form>
    reveal_type(sub_a | sub_b)  # revealed: <types.UnionType special-form>

class C[T]: ...
class D[T]: ...

reveal_type(C | D)  # revealed: <types.UnionType special-form 'C[Unknown] | D[Unknown]'>

reveal_type(C[int] | D[str])  # revealed: <types.UnionType special-form 'C[int] | D[str]'>