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gh-96130: Rephrase use of "typecheck" verb for clarity #98144

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Oct 12, 2022
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gh-96130: Rephrase use of "typecheck" verb for clarity #98144

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20 changes: 10 additions & 10 deletions Doc/library/typing.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,7 @@ A type alias is defined by assigning the type to the alias. In this example,
def scale(scalar: float, vector: Vector) -> Vector:
return [scalar * num for num in vector]

# typechecks; a list of floats qualifies as a Vector.
# passes type checking; a list of floats qualifies as a Vector.
new_vector = scale(2.0, [1.0, -4.2, 5.4])

Type aliases are useful for simplifying complex type signatures. For example::
Expand Down Expand Up @@ -147,10 +147,10 @@ of the original type. This is useful in helping catch logical errors::
def get_user_name(user_id: UserId) -> str:
...

# typechecks
# passes type checking
user_a = get_user_name(UserId(42351))

# does not typecheck; an int is not a UserId
# fails type checking; an int is not a UserId
user_b = get_user_name(-1)

You may still perform all ``int`` operations on a variable of type ``UserId``,
Expand All @@ -176,7 +176,7 @@ It is invalid to create a subtype of ``Derived``::

UserId = NewType('UserId', int)

# Fails at runtime and does not typecheck
# Fails at runtime and does not pass type checking
class AdminUserId(UserId): pass

However, it is possible to create a :class:`NewType` based on a 'derived' ``NewType``::
Expand Down Expand Up @@ -463,12 +463,12 @@ value of type :data:`Any` and assign it to any variable::
s = a # OK

def foo(item: Any) -> int:
# Typechecks; 'item' could be any type,
# Passes type checking; 'item' could be any type,
# and that type might have a 'bar' method
item.bar()
...

Notice that no typechecking is performed when assigning a value of type
Notice that no type checking is performed when assigning a value of type
:data:`Any` to a more precise type. For example, the static type checker did
not report an error when assigning ``a`` to ``s`` even though ``s`` was
declared to be of type :class:`str` and receives an :class:`int` value at
Expand Down Expand Up @@ -500,20 +500,20 @@ reject almost all operations on it, and assigning it to a variable (or using
it as a return value) of a more specialized type is a type error. For example::

def hash_a(item: object) -> int:
# Fails; an object does not have a 'magic' method.
# Fails type checking; an object does not have a 'magic' method.
item.magic()
...

def hash_b(item: Any) -> int:
# Typechecks
# Passes type checking
item.magic()
...

# Typechecks, since ints and strs are subclasses of object
# Passes type checking, since ints and strs are subclasses of object
hash_a(42)
hash_a("foo")

# Typechecks, since Any is compatible with all types
# Passes type checking, since Any is compatible with all types
hash_b(42)
hash_b("foo")

Expand Down