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Merged
merged 2 commits into from
Sep 8, 2022
Merged

Allow @final on TypedDict #13557

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623a332
Allow `@final` on `TypedDict`
godlygeek Aug 30, 2022
88faf74
Merge branch 'master' into final_typeddicts
hauntsaninja Sep 2, 2022
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4 changes: 2 additions & 2 deletions mypy/semanal.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1469,8 +1469,8 @@ def analyze_typeddict_classdef(self, defn: ClassDef) -> bool:
for decorator in defn.decorators:
decorator.accept(self)
if isinstance(decorator, RefExpr):
if decorator.fullname in FINAL_DECORATOR_NAMES:
self.fail("@final cannot be used with TypedDict", decorator)
if decorator.fullname in FINAL_DECORATOR_NAMES and info is not None:
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What if the info is None? Does that happen if there's a circular reference? It would be good to get a test covering that code path.

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It could be FakeInfo for some reason.

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What if the info is None? Does that happen if there's a circular reference?

When there's a forward declaration in the TypedDict body, analyze_typeddict_classdef gets called multiple times. info is initially None in that case, but eventually it's a TypeInfo.

It would be good to get a test covering that code path.

Done.

It could be FakeInfo for some reason.

When would that happen?

info.is_final = True
if info is None:
self.mark_incomplete(defn.name, defn)
else:
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5 changes: 4 additions & 1 deletion mypy/semanal_typeddict.py
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Expand Up @@ -4,7 +4,7 @@

from typing_extensions import Final

from mypy import errorcodes as codes
from mypy import errorcodes as codes, message_registry
from mypy.errorcodes import ErrorCode
from mypy.exprtotype import TypeTranslationError, expr_to_unanalyzed_type
from mypy.messages import MessageBuilder
Expand Down Expand Up @@ -79,6 +79,9 @@ def analyze_typeddict_classdef(self, defn: ClassDef) -> tuple[bool, TypeInfo | N
self.api.accept(base_expr)
if base_expr.fullname in TPDICT_NAMES or self.is_typeddict(base_expr):
possible = True
if isinstance(base_expr.node, TypeInfo) and base_expr.node.is_final:
err = message_registry.CANNOT_INHERIT_FROM_FINAL
self.fail(err.format(base_expr.node.name).value, defn, code=err.code)
if not possible:
return False, None
existing_info = None
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23 changes: 21 additions & 2 deletions test-data/unit/check-typeddict.test
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Expand Up @@ -2012,16 +2012,35 @@ v = {bad2: 2} # E: Extra key "bad" for TypedDict "Value"
[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]

[case testCannotUseFinalDecoratorWithTypedDict]
[case testCannotSubclassFinalTypedDict]
from typing import TypedDict
from typing_extensions import final

@final # E: @final cannot be used with TypedDict
@final
class DummyTypedDict(TypedDict):
int_val: int
float_val: float
str_val: str

class SubType(DummyTypedDict): # E: Cannot inherit from final class "DummyTypedDict"
pass

[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]

[case testCannotSubclassFinalTypedDictWithForwardDeclarations]
from typing import TypedDict
from typing_extensions import final

@final
class DummyTypedDict(TypedDict):
forward_declared: "ForwardDeclared"

class SubType(DummyTypedDict): # E: Cannot inherit from final class "DummyTypedDict"
pass

class ForwardDeclared: pass

[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]

Expand Down