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fix: preserve TypedDict get precision through TypeVar bounds #22068

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fix: preserve TypedDict get precision through TypeVar bounds #22068

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11 changes: 11 additions & 0 deletions mypy/checkexpr.py
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Original file line number Diff line number Diff line change
Expand Up @@ -694,6 +694,17 @@ def method_fullname(self, object_type: Type, method_name: str) -> str | None:
elif isinstance(object_type, TypeType):
object_type = object_type.item

# A TypeVar has no qualified name of its own. For `.get`, resolve a
# TypedDict upper bound through the same fallback owner as a direct
# TypedDict (typing.Mapping.get) so the existing hooks can run. The
# original receiver type is left unchanged outside this lookup. Other
# methods stay unnamed: their hooks assume a TypedDict receiver and
# would rewrite signatures for a TypeVar. Other bound kinds are unchanged.
if isinstance(object_type, TypeVarType) and method_name == "get":
bound = get_proper_type(object_type.upper_bound)
if isinstance(bound, TypedDictType):
object_type = bound

type_name = None
if isinstance(object_type, Instance):
type_name = object_type.type.fullname
Expand Down
32 changes: 22 additions & 10 deletions mypy/plugins/default.py
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Original file line number Diff line number Diff line change
Expand Up @@ -226,15 +226,30 @@ def len_callback(ctx: FunctionContext) -> Type:
return ctx.default_return_type


def _typed_dict_get_receiver(typ: Type) -> TypedDictType | None:
"""TypedDict for `.get`, including a TypeVar's proper upper bound.

The plugin context still carries the original receiver. Callers use this
only for field lookup, required keys, and closedness.
"""
typ = get_proper_type(typ)
if isinstance(typ, TypeVarType):
typ = get_proper_type(typ.upper_bound)
if isinstance(typ, TypedDictType):
return typ
return None


def typed_dict_get_signature_callback(ctx: MethodSigContext) -> CallableType:
"""Try to infer a better signature type for TypedDict.get.

This is used to get better type context for the second argument that
depends on a TypedDict value type.
"""
signature = ctx.default_signature
receiver = _typed_dict_get_receiver(ctx.type)
if (
isinstance(ctx.type, TypedDictType)
receiver is not None
and len(ctx.args) == 2
and len(ctx.args[0]) == 1
and isinstance(ctx.args[0][0], StrExpr)
Expand All @@ -243,7 +258,7 @@ def typed_dict_get_signature_callback(ctx: MethodSigContext) -> CallableType:
and len(ctx.args[1]) == 1
):
key = ctx.args[0][0].value
value_type = get_proper_type(ctx.type.items.get(key))
value_type = get_proper_type(receiver.items.get(key))
ret_type = signature.ret_type
if value_type:
default_arg = ctx.args[1][0]
Expand All @@ -268,11 +283,8 @@ def typed_dict_get_signature_callback(ctx: MethodSigContext) -> CallableType:

def typed_dict_get_callback(ctx: MethodContext) -> Type:
"""Infer a precise return type for TypedDict.get with literal first argument."""
if (
isinstance(ctx.type, TypedDictType)
and len(ctx.arg_types) >= 1
and len(ctx.arg_types[0]) == 1
):
receiver = _typed_dict_get_receiver(ctx.type)
if receiver is not None and len(ctx.arg_types) >= 1 and len(ctx.arg_types[0]) == 1:
keys = try_getting_str_literals(ctx.args[0][0], ctx.arg_types[0][0])
if keys is None:
return ctx.default_return_type
Expand All @@ -290,12 +302,12 @@ def typed_dict_get_callback(ctx: MethodContext) -> Type:

output_types: list[Type] = []
for key in keys:
value_type: Type | None = ctx.type.items.get(key)
value_type: Type | None = receiver.items.get(key)
if value_type is None:
if not ctx.type.is_closed:
if not receiver.is_closed:
return ctx.default_return_type
output_types.append(default_type)
elif key in ctx.type.required_keys:
elif key in receiver.required_keys:
output_types.append(value_type)
else:
# HACK to deal with get(key, {})
Expand Down
45 changes: 45 additions & 0 deletions test-data/unit/check-python312.test
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Original file line number Diff line number Diff line change
Expand Up @@ -2401,3 +2401,48 @@ reveal_type(baz(objs)) # N: Revealed type is "builtins.list[__main__.B | __main
reveal_type(baz(objs_a)) # N: Revealed type is "builtins.list[__main__.B | __main__.C]"
[builtins fixtures/tuple.pyi]
[typing fixtures/typing-full.pyi]

[case testPEP695TypedDictGetBound]
# https://github.com/python/mypy/issues/16872
from typing import TypedDict

class MyDict(TypedDict):
foo: list[str]
bar: int

class Partial(TypedDict, total=False):
foo: list[str]
bar: int

class Child(MyDict):
extra: int

def required[T: MyDict](d: T, direct: MyDict) -> T:
reveal_type(d) # N: Revealed type is "T`-1"
reveal_type(d['foo']) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(direct['foo']) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(d.get('foo')) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(direct.get('foo')) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(d.get('foo', ['x'])) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(direct.get('foo', ['x'])) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(d.get('bar')) # N: Revealed type is "builtins.int"
reveal_type(direct.get('bar', 0)) # N: Revealed type is "builtins.int"
reveal_type(d.get('bar', 0)) # N: Revealed type is "builtins.int"
return d

def optional[T: Partial](d: T, direct: Partial) -> T:
reveal_type(d.get('foo')) # N: Revealed type is "builtins.list[builtins.str] | None"
reveal_type(direct.get('foo')) # N: Revealed type is "builtins.list[builtins.str] | None"
reveal_type(d.get('bar', None)) # N: Revealed type is "builtins.int | None"
reveal_type(direct.get('bar', None)) # N: Revealed type is "builtins.int | None"
reveal_type(d.get('foo', [])) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(direct.get('foo', [])) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(d.get('bar', 1)) # N: Revealed type is "builtins.int"
reveal_type(direct.get('bar', 1)) # N: Revealed type is "builtins.int"
return d

def use(child: Child, partial: Partial) -> None:
reveal_type(required(child, child)) # N: Revealed type is "TypedDict('__main__.Child', {'foo': builtins.list[builtins.str], 'bar': builtins.int, 'extra': builtins.int})"
reveal_type(optional(partial, partial)) # N: Revealed type is "TypedDict('__main__.Partial', {'foo'?: builtins.list[builtins.str], 'bar'?: builtins.int})"
[builtins fixtures/tuple.pyi]
[typing fixtures/typing-full.pyi]
205 changes: 205 additions & 0 deletions test-data/unit/check-typeddict.test
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Original file line number Diff line number Diff line change
Expand Up @@ -6148,3 +6148,208 @@ def test(f: Callable[[object], object]) -> None: ...
test(foo) # E: Argument 1 to "test" has incompatible type overloaded function; expected "Callable[[object], object]"
[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]

[case testTypedDictGetBoundTypeVarRequired]
# https://github.com/python/mypy/issues/16872
from typing import TypedDict, TypeVar

class MyDict(TypedDict):
foo: list[str]

class Child(MyDict):
extra: int

class Unrelated: pass

T = TypeVar('T', bound=MyDict)

def f(d: T, direct: MyDict, u: Unrelated) -> T:
reveal_type(d) # N: Revealed type is "T`-1"
reveal_type(d['foo']) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(direct['foo']) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(d.get('foo')) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(direct.get('foo')) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(d.get('foo', ['x'])) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(direct.get('foo', ['x'])) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(d.get('foo', [])) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(direct.get('foo', [])) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(d.get('foo', u)) # N: Revealed type is "builtins.list[builtins.str]"
reveal_type(direct.get('foo', u)) # N: Revealed type is "builtins.list[builtins.str]"
return d

def g(child: Child) -> None:
reveal_type(f(child, child, Unrelated())) # N: Revealed type is "TypedDict('__main__.Child', {'foo': builtins.list[builtins.str], 'extra': builtins.int})"
[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]

[case testTypedDictGetBoundTypeVarOptional]
from typing import TypedDict, TypeVar
from typing_extensions import NotRequired, Required

class Unrelated: pass

class Partial(TypedDict, total=False):
x: int
y: str

class Mixed(TypedDict):
x: Required[int]
y: NotRequired[str]

P = TypeVar('P', bound=Partial)
M = TypeVar('M', bound=Mixed)

def partial(d: P, direct: Partial, u: Unrelated) -> None:
reveal_type(d.get('x')) # N: Revealed type is "builtins.int | None"
reveal_type(direct.get('x')) # N: Revealed type is "builtins.int | None"
reveal_type(d.get('y', u)) # N: Revealed type is "builtins.str | __main__.Unrelated"
reveal_type(direct.get('y', u)) # N: Revealed type is "builtins.str | __main__.Unrelated"
reveal_type(d.get('x', 1)) # N: Revealed type is "builtins.int"
reveal_type(direct.get('x', 1)) # N: Revealed type is "builtins.int"
reveal_type(d.get('y', None)) # N: Revealed type is "builtins.str | None"
reveal_type(direct.get('y', None)) # N: Revealed type is "builtins.str | None"

def mixed(d: M, direct: Mixed, u: Unrelated) -> None:
reveal_type(d.get('x')) # N: Revealed type is "builtins.int"
reveal_type(direct.get('x')) # N: Revealed type is "builtins.int"
reveal_type(d.get('y')) # N: Revealed type is "builtins.str | None"
reveal_type(direct.get('y')) # N: Revealed type is "builtins.str | None"
reveal_type(d.get('x', u)) # N: Revealed type is "builtins.int"
reveal_type(direct.get('x', u)) # N: Revealed type is "builtins.int"
reveal_type(d.get('y', u)) # N: Revealed type is "builtins.str | __main__.Unrelated"
reveal_type(direct.get('y', u)) # N: Revealed type is "builtins.str | __main__.Unrelated"
reveal_type(d.get('y', 'a')) # N: Revealed type is "builtins.str"
reveal_type(direct.get('y', 'a')) # N: Revealed type is "builtins.str"
reveal_type(d.get('x', 1)) # N: Revealed type is "builtins.int"
reveal_type(direct.get('x', 1)) # N: Revealed type is "builtins.int"
[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]

[case testTypedDictGetBoundTypeVarTypeContext]
from typing import TypedDict, TypeVar

class Inner(TypedDict):
a: int

class Outer(TypedDict, total=False):
items: list[int]
nested: Inner

class TotalOuter(TypedDict):
nested: Inner
items: list[int]

T = TypeVar('T', bound=Outer)
U = TypeVar('U', bound=TotalOuter)

def optional(d: T, direct: Outer) -> None:
reveal_type(d.get('items', [])) # N: Revealed type is "builtins.list[builtins.int]"
reveal_type(direct.get('items', [])) # N: Revealed type is "builtins.list[builtins.int]"
reveal_type(d.get('nested', {})) # N: Revealed type is "TypedDict('__main__.Inner', {'a'?: builtins.int})"
reveal_type(direct.get('nested', {})) # N: Revealed type is "TypedDict('__main__.Inner', {'a'?: builtins.int})"
reveal_type(d.get('nested', {}).get('a')) # N: Revealed type is "builtins.int | None"
reveal_type(direct.get('nested', {}).get('a')) # N: Revealed type is "builtins.int | None"
reveal_type(d.get('nested', {})['a']) # N: Revealed type is "builtins.int"
reveal_type(direct.get('nested', {})['a']) # N: Revealed type is "builtins.int"

def required(d: U, direct: TotalOuter) -> None:
reveal_type(d.get('nested', {})) # N: Revealed type is "TypedDict('__main__.Inner', {'a': builtins.int})"
reveal_type(direct.get('nested', {})) # N: Revealed type is "TypedDict('__main__.Inner', {'a': builtins.int})"
reveal_type(d.get('nested', {}).get('a')) # N: Revealed type is "builtins.int"
reveal_type(direct.get('nested', {}).get('a')) # N: Revealed type is "builtins.int"
reveal_type(d.get('items', [])) # N: Revealed type is "builtins.list[builtins.int]"
reveal_type(direct.get('items', [])) # N: Revealed type is "builtins.list[builtins.int]"
[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]

[case testTypedDictGetBoundTypeVarLiteralKeys]
from typing import Literal, TypedDict, TypeVar
from typing_extensions import NotRequired, Required

class Unrelated: pass

class Open(TypedDict):
x: Required[int]
y: Required[str]
z: NotRequired[str]

T = TypeVar('T', bound=Open)

def f(d: T, direct: Open, u: Unrelated) -> None:
x: Literal['x']
y: Literal['y']
z: Literal['z']
missing: Literal['missing']
x_or_y: Literal['x', 'y']
x_or_z: Literal['x', 'z']
y_or_missing: Literal['y', 'missing']
s = ''

reveal_type(d.get(x)) # N: Revealed type is "builtins.int"
reveal_type(direct.get(x)) # N: Revealed type is "builtins.int"
reveal_type(d.get(y, u)) # N: Revealed type is "builtins.str"
reveal_type(direct.get(y, u)) # N: Revealed type is "builtins.str"
reveal_type(d.get(z)) # N: Revealed type is "builtins.str | None"
reveal_type(direct.get(z)) # N: Revealed type is "builtins.str | None"
reveal_type(d.get(z, u)) # N: Revealed type is "builtins.str | __main__.Unrelated"
reveal_type(direct.get(z, u)) # N: Revealed type is "builtins.str | __main__.Unrelated"
reveal_type(d.get(z, 'a')) # N: Revealed type is "builtins.str"
reveal_type(direct.get(z, 'a')) # N: Revealed type is "builtins.str"
reveal_type(d.get(x_or_y)) # N: Revealed type is "builtins.int | builtins.str"
reveal_type(direct.get(x_or_y)) # N: Revealed type is "builtins.int | builtins.str"
reveal_type(d.get(x_or_y, u)) # N: Revealed type is "builtins.int | builtins.str"
reveal_type(direct.get(x_or_y, u)) # N: Revealed type is "builtins.int | builtins.str"
reveal_type(d.get(x_or_z)) # N: Revealed type is "builtins.int | builtins.str | None"
reveal_type(direct.get(x_or_z)) # N: Revealed type is "builtins.int | builtins.str | None"
reveal_type(d.get(x_or_z, u)) # N: Revealed type is "builtins.int | builtins.str | __main__.Unrelated"
reveal_type(direct.get(x_or_z, u)) # N: Revealed type is "builtins.int | builtins.str | __main__.Unrelated"
reveal_type(d.get(missing)) # N: Revealed type is "builtins.object"
reveal_type(direct.get(missing)) # N: Revealed type is "builtins.object"
reveal_type(d.get('missing')) # N: Revealed type is "builtins.object"
reveal_type(direct.get('missing')) # N: Revealed type is "builtins.object"
reveal_type(d.get(y_or_missing)) # N: Revealed type is "builtins.object"
reveal_type(direct.get(y_or_missing)) # N: Revealed type is "builtins.object"
reveal_type(d.get(y_or_missing, u)) # N: Revealed type is "builtins.object"
reveal_type(direct.get(y_or_missing, u)) # N: Revealed type is "builtins.object"
reveal_type(d.get(s)) # N: Revealed type is "builtins.object"
reveal_type(direct.get(s)) # N: Revealed type is "builtins.object"
[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]

[case testTypedDictGetBoundTypeVarInvalidArgs]
from typing import TypedDict, TypeVar

class MyDict(TypedDict):
x: int
y: str

T = TypeVar('T', bound=MyDict)

def f(d: T) -> None:
d.get() # E: All overload variants of "get" of "Mapping" require at least one argument \
# N: Possible overload variants: \
# N: def get(self, str, /) -> object \
# N: def get(self, str, object, /) -> object \
# N: def [V] get(self, str, V, /) -> object
d.get('x', 1, 2) # E: No overload variant of "get" of "Mapping" matches argument types "str", "int", "int" \
# N: Possible overload variants: \
# N: def get(self, str, /) -> object \
# N: def get(self, str, object, /) -> object \
# N: def [V] get(self, str, int | V, /) -> object
d.get('x', 1 + 'y') # E: Unsupported operand types for + ("int" and "str")
s = ''
reveal_type(d.get(s)) # N: Revealed type is "builtins.object"
reveal_type(d.get('z')) # N: Revealed type is "builtins.object"
[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]

[case testTypedDictGetBoundTypeVarUnrelated]
from typing import TypeVar

D = TypeVar('D', bound=dict[str, int])

def f(d: D) -> None:
reveal_type(d.get('x')) # N: Revealed type is "builtins.int | None"
reveal_type(d.get('x', 1)) # N: Revealed type is "builtins.int"
[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]
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