[3.7] bpo-37814: Document the empty tuple type annotation syntax (GH-15208) (GH-15262)

https://bugs.python.org/issue37814:

> The empty tuple syntax in type annotations, `Tuple[()]`, is not obvious from the examples given in the documentation (I naively expected `Tuple[]` to work); it has been documented in PEP 484 and in mypy, but not in the documentation for the typing module.

https://bugs.python.org/issue37814
(cherry picked from commit 8a784af750fa82c8355903309e5089eb2b60c16b)

Co-authored-by: Josh Holland <anowlcalledjosh@gmail.com>
https://bugs.python.org/issue37814

Automerge-Triggered-By: @gvanrossum

diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst
index 5adc81c1e3c8c4a5617ce3f83c5e642bf1179359..c0b048cb2bd33373927d33d057a13c94a95ed1cf 100644 (file)
--- a/Doc/library/typing.rst
+++ b/Doc/library/typing.rst
@@ -1056,7 +1056,8 @@ The module defines the following classes, functions and decorators:
 .. data:: Tuple
 
    Tuple type; ``Tuple[X, Y]`` is the type of a tuple of two items
-   with the first item of type X and the second of type Y.
+   with the first item of type X and the second of type Y. The type of
+   the empty tuple can be written as ``Tuple[()]``.
 
    Example: ``Tuple[T1, T2]`` is a tuple of two elements corresponding
    to type variables T1 and T2.  ``Tuple[int, float, str]`` is a tuple