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Support @no_type_check for classes #10162

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Support @no_type_check for classes #10162

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7 changes: 6 additions & 1 deletion mypy/checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1720,7 +1720,10 @@ def visit_class_def(self, defn: ClassDef) -> None:
self.binder = ConditionalTypeBinder()
with self.binder.top_frame_context():
with self.scope.push_class(defn.info):
self.accept(defn.defs)
if not any(refers_to_fullname(decorator,
'typing.no_type_check')
for decorator in defn.decorators):
self.accept(defn.defs)
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Type checking populates some information that other parts of the type checker may rely on. So this needs to be more elaborate.

For example, this shouldn't generate errors:

import typing

@typing.no_type_check
class A:
    a = int()

    def f(self) -> None:
        self.b = int()

a = A()
a.a  # Cannot determine type of "a"
a.b  # Cannot determine type of "b"

One way to deal with this is to give everything in the class the type Any. We'd still no type checking, but it actually wouldn't do much. We use in_checked_function() in mypy.checker to do this. You can add some check for no_type_check decorator there (maybe via a bool attribute flag) so that in_checked_function() returns False inside the class.

self.binder = old_binder
if not (defn.info.typeddict_type or defn.info.tuple_type or defn.info.is_enum):
# If it is not a normal class (not a special form) check class keywords.
Expand All @@ -1733,6 +1736,8 @@ def visit_class_def(self, defn: ClassDef) -> None:
sig = type_object_type(defn.info, self.named_type) # type: Type
# Decorators are applied in reverse order.
for decorator in reversed(defn.decorators):
if refers_to_fullname(decorator, 'typing.no_type_check'):
continue
if (isinstance(decorator, CallExpr)
and isinstance(decorator.analyzed, PromoteExpr)):
# _promote is a special type checking related construct.
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9 changes: 9 additions & 0 deletions test-data/unit/check-classes.test
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Original file line number Diff line number Diff line change
Expand Up @@ -388,6 +388,15 @@ class A:
class B(A): # E: Missing positional argument "x" in call to "__init_subclass__" of "A"
def __init_subclass__(cls) -> None: pass

[case testNoTypeCheckDecoratorOnClass]
import typing

@typing.no_type_check
class A:
def f(self) -> None:
1 + 'x'
[typing fixtures/typing-medium.pyi]

[case testOverrideWithDecorator]
from typing import Callable

Expand Down