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Rename TypeExpr to TypeForm #475

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merged 4 commits into from
Sep 28, 2024
Merged

Rename TypeExpr to TypeForm #475

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0a3814a
Rename TypeExpr to TypeForm
JelleZijlstra Sep 28, 2024
dd544ac
Merge remote-tracking branch 'upstream/main' into typeform
JelleZijlstra Sep 28, 2024
4935e81
shorten
JelleZijlstra Sep 28, 2024
1f71724
rewrite docstring
JelleZijlstra Sep 28, 2024
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2 changes: 1 addition & 1 deletion CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
# Unreleased

- Add `typing_extensions.TypeExpr` from PEP 747. Patch by
- Add `typing_extensions.TypeForm` from PEP 747. Patch by
Jelle Zijlstra.
- Add `typing_extensions.get_annotations`, a backport of
`inspect.get_annotations` that adds features specified
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2 changes: 1 addition & 1 deletion doc/index.rst
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Expand Up @@ -367,7 +367,7 @@ Special typing primitives

.. versionadded:: 4.6.0

.. data:: TypeExpr
.. data:: TypeForm

See :pep:`747`. A type hint representing a type expression.

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46 changes: 23 additions & 23 deletions src/test_typing_extensions.py
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Expand Up @@ -70,7 +70,7 @@
TypeAlias,
TypeAliasType,
TypedDict,
TypeExpr,
TypeForm,
TypeGuard,
TypeIs,
TypeVar,
Expand Down Expand Up @@ -5508,33 +5508,33 @@ def test_no_isinstance(self):
issubclass(int, TypeIs)


class TypeExprTests(BaseTestCase):
class TypeFormTests(BaseTestCase):
def test_basics(self):
TypeExpr[int] # OK
self.assertEqual(TypeExpr[int], TypeExpr[int])
TypeForm[int] # OK
self.assertEqual(TypeForm[int], TypeForm[int])

def foo(arg) -> TypeExpr[int]: ...
self.assertEqual(gth(foo), {'return': TypeExpr[int]})
def foo(arg) -> TypeForm[int]: ...
self.assertEqual(gth(foo), {'return': TypeForm[int]})

def test_repr(self):
if hasattr(typing, 'TypeExpr'):
if hasattr(typing, 'TypeForm'):
mod_name = 'typing'
else:
mod_name = 'typing_extensions'
self.assertEqual(repr(TypeExpr), f'{mod_name}.TypeExpr')
cv = TypeExpr[int]
self.assertEqual(repr(cv), f'{mod_name}.TypeExpr[int]')
cv = TypeExpr[Employee]
self.assertEqual(repr(cv), f'{mod_name}.TypeExpr[{__name__}.Employee]')
cv = TypeExpr[Tuple[int]]
self.assertEqual(repr(cv), f'{mod_name}.TypeExpr[typing.Tuple[int]]')
self.assertEqual(repr(TypeForm), f'{mod_name}.TypeForm')
cv = TypeForm[int]
self.assertEqual(repr(cv), f'{mod_name}.TypeForm[int]')
cv = TypeForm[Employee]
self.assertEqual(repr(cv), f'{mod_name}.TypeForm[{__name__}.Employee]')
cv = TypeForm[Tuple[int]]
self.assertEqual(repr(cv), f'{mod_name}.TypeForm[typing.Tuple[int]]')

def test_cannot_subclass(self):
with self.assertRaises(TypeError):
class C(type(TypeExpr)):
class C(type(TypeForm)):
pass
with self.assertRaises(TypeError):
class D(type(TypeExpr[int])):
class D(type(TypeForm[int])):
pass

def test_call(self):
Expand All @@ -5546,24 +5546,24 @@ def test_call(self):
]
for obj in objs:
with self.subTest(obj=obj):
self.assertIs(TypeExpr(obj), obj)
self.assertIs(TypeForm(obj), obj)

with self.assertRaises(TypeError):
TypeExpr()
TypeForm()
with self.assertRaises(TypeError):
TypeExpr("too", "many")
TypeForm("too", "many")

def test_cannot_init_type(self):
with self.assertRaises(TypeError):
type(TypeExpr)()
type(TypeForm)()
with self.assertRaises(TypeError):
type(TypeExpr[Optional[int]])()
type(TypeForm[Optional[int]])()

def test_no_isinstance(self):
with self.assertRaises(TypeError):
isinstance(1, TypeExpr[int])
isinstance(1, TypeForm[int])
with self.assertRaises(TypeError):
issubclass(int, TypeExpr)
issubclass(int, TypeForm)


class LiteralStringTests(BaseTestCase):
Expand Down
40 changes: 25 additions & 15 deletions src/typing_extensions.py
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Expand Up @@ -86,7 +86,7 @@
'Text',
'TypeAlias',
'TypeAliasType',
'TypeExpr',
'TypeForm',
'TypeGuard',
'TypeIs',
'TYPE_CHECKING',
Expand Down Expand Up @@ -2047,23 +2047,28 @@ def f(val: Union[int, Awaitable[int]]) -> int:
""")

# 3.14+?
if hasattr(typing, 'TypeExpr'):
TypeExpr = typing.TypeExpr
if hasattr(typing, 'TypeForm'):
TypeForm = typing.TypeForm
# 3.9
elif sys.version_info[:2] >= (3, 9):
class _TypeExprForm(_ExtensionsSpecialForm, _root=True):
# TypeExpr(X) is equivalent to X but indicates to the type checker
# that the object is a TypeExpr.
class _TypeFormForm(_ExtensionsSpecialForm, _root=True):
# TypeForm(X) is equivalent to X but indicates to the type checker
# that the object is a TypeForm.
def __call__(self, obj, /):
return obj

@_TypeExprForm
def TypeExpr(self, parameters):
"""Special typing form used to represent a type expression.
@_TypeFormForm
def TypeForm(self, parameters):
"""A special typing construct to represent valid type expressions.
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This phrasing is subtly confusing in the same way that earlier drafts of the PEP were. A TypeForm doesn't represent a type expression. It represents the set of runtime objects that encode the information in a type expression. This is the reason we moved away from the TypeExpr terminology. I recommend using the phrasing from the latest draft of the PEP. I tried hard to make that phrasing as clear as possible to avoid such confusion.

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Thanks, I rewrote the docstring to align with the Specification section of PEP 747.


Expressions are assignable to TypeForm if they represent valid type
expressions. For example, ``int`` is assignable to ``TypeForm`` (because
``int``, as a type, is a valid type expression), but ``1`` is not (because
integers are not valid type expressions).

Usage:

def cast[T](typ: TypeExpr[T], value: Any) -> T: ...
def cast[T](typ: TypeForm[T], value: Any) -> T: ...

reveal_type(cast(int, "x")) # int

Expand All @@ -2073,7 +2078,7 @@ def cast[T](typ: TypeExpr[T], value: Any) -> T: ...
return typing._GenericAlias(self, (item,))
# 3.8
else:
class _TypeExprForm(_ExtensionsSpecialForm, _root=True):
class _TypeFormForm(_ExtensionsSpecialForm, _root=True):
def __getitem__(self, parameters):
item = typing._type_check(parameters,
f'{self._name} accepts only a single type')
Expand All @@ -2082,13 +2087,18 @@ def __getitem__(self, parameters):
def __call__(self, obj, /):
return obj

TypeExpr = _TypeExprForm(
'TypeExpr',
doc="""Special typing form used to represent a type expression.
TypeForm = _TypeFormForm(
'TypeForm',
doc="""A special typing construct to represent valid type expressions.

Expressions are assignable to TypeForm if they represent valid type
expressions. For example, ``int`` is assignable to ``TypeForm`` (because
``int``, as a type, is a valid type expression), but ``1`` is not (because
integers are not valid type expressions).

Usage:

def cast[T](typ: TypeExpr[T], value: Any) -> T: ...
def cast[T](typ: TypeForm[T], value: Any) -> T: ...

reveal_type(cast(int, "x")) # int

Expand Down
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