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Made proposed change to the typing spec with regard to NoReturn and… #1570

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Jan 12, 2024
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Made proposed change to the typing spec with regard to NoReturn and… #1570

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23 changes: 7 additions & 16 deletions docs/spec/special-types.rst
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Expand Up @@ -85,25 +85,16 @@ is unreachable and will behave accordingly::
return 'whatever works' # Error might be not reported by some checkers
# that ignore errors in unreachable blocks

The ``NoReturn`` type is only valid as a return annotation of functions,
and considered an error if it appears in other positions::

from typing import NoReturn

# All of the following are errors
def bad1(x: NoReturn) -> int:
...
bad2: NoReturn = None
def bad3() -> list[NoReturn]:
...

``Never``
---------

Since Python 3.11, the ``typing`` module has a primitive ``Never``. This
represents the bottom type, a type that has no members. Type checkers are
expected to treat this type as equivalent to ``NoReturn``, but it is explicitly
also allowed in argument positions.
Since Python 3.11, the ``typing`` module contains a primitive ``Never``. It
represents the bottom type, a type that has no members.

The ``Never`` type is equivalent to ``NoReturn``, which is discussed above.
The ``NoReturn`` type is conventionally used in return annotations of
functions, and ``Never`` is typically used in other locations, but the two
types are completely interchangeable.

Tuples
------
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