diff --git a/mypy/plugins/attrs.py b/mypy/plugins/attrs.py index c71d898e1c62a..6a506dec90ea1 100644 --- a/mypy/plugins/attrs.py +++ b/mypy/plugins/attrs.py @@ -8,6 +8,7 @@ import mypy.plugin # To avoid circular imports. from mypy.checker import TypeChecker from mypy.errorcodes import LITERAL_REQ +from mypy.expandtype import expand_type from mypy.exprtotype import TypeTranslationError, expr_to_unanalyzed_type from mypy.messages import format_type_bare from mypy.nodes import ( @@ -49,7 +50,7 @@ deserialize_and_fixup_type, ) from mypy.server.trigger import make_wildcard_trigger -from mypy.typeops import make_simplified_union, map_type_from_supertype +from mypy.typeops import get_type_vars, make_simplified_union, map_type_from_supertype from mypy.types import ( AnyType, CallableType, @@ -61,6 +62,7 @@ TupleType, Type, TypeOfAny, + TypeVarId, TypeVarType, UnionType, get_proper_type, @@ -85,8 +87,9 @@ class Converter: """Holds information about a `converter=` argument""" - def __init__(self, init_type: Type | None = None) -> None: + def __init__(self, init_type: Type | None = None, ret_type: Type | None = None) -> None: self.init_type = init_type + self.ret_type = ret_type class Attribute: @@ -115,11 +118,20 @@ def __init__( def argument(self, ctx: mypy.plugin.ClassDefContext) -> Argument: """Return this attribute as an argument to __init__.""" assert self.init - init_type: Type | None = None if self.converter: if self.converter.init_type: init_type = self.converter.init_type + if init_type and self.converter.ret_type: + # The converter return type should be the same type as the attribute type. + # Copy type vars from attr type to converter. + converter_vars = get_type_vars(self.converter.ret_type) + init_vars = get_type_vars(self.init_type) + if converter_vars and len(converter_vars) == len(init_vars): + variables = { + binder.id: arg for binder, arg in zip(converter_vars, init_vars) + } + init_type = expand_type(init_type, variables) else: ctx.api.fail("Cannot determine __init__ type from converter", self.context) init_type = AnyType(TypeOfAny.from_error) @@ -671,6 +683,8 @@ def _parse_converter( converter_type = get_proper_type(converter_type) if isinstance(converter_type, CallableType) and converter_type.arg_types: converter_info.init_type = converter_type.arg_types[0] + if not is_attr_converters_optional: + converter_info.ret_type = converter_type.ret_type elif isinstance(converter_type, Overloaded): types: list[Type] = [] for item in converter_type.items: diff --git a/test-data/unit/check-attr.test b/test-data/unit/check-attr.test index 83a441aca2330..3784630d73d1d 100644 --- a/test-data/unit/check-attr.test +++ b/test-data/unit/check-attr.test @@ -469,6 +469,48 @@ A([1], '2') # E: Cannot infer type argument 1 of "A" [builtins fixtures/list.pyi] +[case testAttrsGenericWithConverter] +from typing import TypeVar, Generic, List, Iterable, Iterator +import attr +T = TypeVar('T') + +def int_gen() -> Iterator[int]: + yield 1 + +def list_converter(x: Iterable[T]) -> List[T]: + return list(x) + +@attr.s(auto_attribs=True) +class A(Generic[T]): + x: List[T] = attr.ib(converter=list_converter) + y: T = attr.ib() + def foo(self) -> List[T]: + return [self.y] + def bar(self) -> T: + return self.x[0] + def problem(self) -> T: + return self.x # E: Incompatible return value type (got "List[T]", expected "T") +reveal_type(A) # N: Revealed type is "def [T] (x: typing.Iterable[T`1], y: T`1) -> __main__.A[T`1]" +a1 = A([1], 2) +reveal_type(a1) # N: Revealed type is "__main__.A[builtins.int]" +reveal_type(a1.x) # N: Revealed type is "builtins.list[builtins.int]" +reveal_type(a1.y) # N: Revealed type is "builtins.int" + +a2 = A(int_gen(), 2) +reveal_type(a2) # N: Revealed type is "__main__.A[builtins.int]" +reveal_type(a2.x) # N: Revealed type is "builtins.list[builtins.int]" +reveal_type(a2.y) # N: Revealed type is "builtins.int" + +# Leaving this as a sanity check +class B(Generic[T]): + def __init__(self, x: Iterable[T], y: T) -> None: + pass + +B(['str'], 7) +B([1], '2') + +[builtins fixtures/list.pyi] + [case testAttrsUntypedGenericInheritance] from typing import Generic, TypeVar