(😳) no error when instanciating `dict` type alias with invalid type

[DetachHead]

from typing import TypeAlias

Values: TypeAlias = dict[str, int]

a = Values(foo="")  # no error

playground

[KotlinIsland]

No emoji in the title; didn't read

Seems to only affect dicts kwarg constructor. I can't repro with any other type.

[KotlinIsland]

It seems to only affect dict: playground

[brianschubert]

The reason this doesn't work is becaused calls to builtins.dict get translsated into DictExprs during semantic analysis (here), which causes the usual call expression analysis to be skipped during type checking (here). The fix to make this work would be trivial (we'd just need to add a check for isinstance(node, DictExpr) to this branch so that the call expression gets analyzed even though the result isn't used). However, I'm not sure that that would be worth doing, since using type aliases for their runtime values is already a bit dubious. The "correct" way to write this would be

a: Values = dict(foo="")

which has the helpful error

error: Dict entry 0 has incompatible type "str": "str"; expected "str": "int"

By comparison, fixing this would result in the less helpful error

error: No overload variant of "dict" matches argument type "str"
note:     def dict(self) -> dict[str, int]
note:     def dict(self, **kwargs: int) -> dict[str, int]
note:     def dict(self, SupportsKeysAndGetItem[str, int], /) -> dict[str, int]
note:     def dict(self, SupportsKeysAndGetItem[str, int], /, **kwargs: int) -> dict[str, int]
note:     def dict(self, Iterable[tuple[str, int]], /) -> dict[str, int]
note:     def dict(self, Iterable[tuple[str, int]], /, **kwargs: int) -> dict[str, int]
note:     def dict(self, Iterable[list[str]], /) -> dict[str, str]
note:     def dict(self, Iterable[list[bytes]], /) -> dict[bytes, bytes]