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charliermarsh · 2026-04-26T23:30:25Z

Summary

Given:

from typing import TypedDict

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

def _(data: TD):
    reveal_type(dict(data))

We now reveal dict[str, object].

We could consider using a narrower value type (e.g., infer dict[str, int] if all values are int), though Mypy and Pyright don't do that (I suppose it wouldn't be sound for open TypedDicts?).

Closes astral-sh/ty#3340.

astral-sh-bot · 2026-04-26T23:32:07Z

Typing conformance results

No changes detected ✅

Current numbers

The percentage of diagnostics emitted that were expected errors held steady at 89.36%. The percentage of expected errors that received a diagnostic held steady at 85.49%. The number of fully passing files held steady at 88/134.

astral-sh-bot · 2026-04-26T23:32:57Z

Memory usage report

Memory usage unchanged ✅

astral-sh-bot · 2026-04-26T23:35:28Z

`ecosystem-analyzer` results

Lint rule	Added	Removed	Changed
`no-matching-overload`	0	23	0
`invalid-argument-type`	0	3	0
Total	0	26	0

Raw diff (26 changes)

aioredis (https://github.com/aio-libs/aioredis)
- aioredis/connection.py:1301:9 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments

core (https://github.com/home-assistant/core)
- homeassistant/components/weather/__init__.py:701:46 error[no-matching-overload] No overload of `dict.__init__` matches arguments
- homeassistant/components/auth/mfa_setup_flow.py:146:16 error[no-matching-overload] No overload of `dict.__init__` matches arguments
- homeassistant/components/fronius/config_flow.py:117:53 error[no-matching-overload] No overload of `dict.__init__` matches arguments
- homeassistant/components/mqtt/config_flow.py:3777:65 error[no-matching-overload] No overload of `dict.__init__` matches arguments
- homeassistant/components/mqtt/config_flow.py:4891:13 error[no-matching-overload] No overload of `dict.__init__` matches arguments
- homeassistant/components/mqtt/config_flow.py:4996:13 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments
- homeassistant/components/mqtt/config_flow.py:4997:13 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments
- homeassistant/components/mqtt/config_flow.py:5035:9 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments
- homeassistant/components/mqtt/config_flow.py:5047:13 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments
- homeassistant/components/mqtt/config_flow.py:5048:13 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments
- homeassistant/components/mqtt/entity.py:386:17 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments
- homeassistant/components/mqtt/entity.py:387:17 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments

cwltool (https://github.com/common-workflow-language/cwltool)
- cwltool/cwlprov/ro.py:359:21 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments

dd-trace-py (https://github.com/DataDog/dd-trace-py)
- ddtrace/llmobs/_prompt_optimization.py:316:49 error[no-matching-overload] No overload of `dict.__init__` matches arguments

discord.py (https://github.com/Rapptz/discord.py)
- discord/client.py:2717:93 error[invalid-argument-type] Argument to bound method `str.format_map` is incorrect: Expected `_FormatMapMapping`, found `TextChannel | NewsChannel | VoiceChannel | ... omitted 7 union elements`
- discord/guild.py:2626:93 error[invalid-argument-type] Argument to bound method `str.format_map` is incorrect: Expected `_FormatMapMapping`, found `TextChannel | NewsChannel | VoiceChannel | ... omitted 7 union elements`
- discord/interactions.py:260:92 error[invalid-argument-type] Argument to bound method `str.format_map` is incorrect: Expected `_FormatMapMapping`, found `TextChannel | NewsChannel | VoiceChannel | ... omitted 7 union elements`

hydpy (https://github.com/hydpy-dev/hydpy)
- hydpy/models/rconc/rconc_control.py:249:23 error[no-matching-overload] No overload of `dict.__init__` matches arguments

packaging (https://github.com/pypa/packaging)
- src/packaging/pylock.py:780:13 error[no-matching-overload] No overload of `dict.__init__` matches arguments

pip (https://github.com/pypa/pip)
- src/pip/_vendor/packaging/pylock.py:775:13 error[no-matching-overload] No overload of `dict.__init__` matches arguments

poetry (https://github.com/python-poetry/poetry)
- src/poetry/utils/authenticator.py:233:9 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments

pydantic (https://github.com/pydantic/pydantic)
- pydantic/_internal/_mock_val_ser.py:41:16 error[no-matching-overload] No overload matches arguments

scikit-learn (https://github.com/scikit-learn/scikit-learn)
- sklearn/externals/array_api_compat/dask/array/_info.py:378:17 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments

scipy (https://github.com/scipy/scipy)
- subprojects/array_api_compat/array_api_compat/array_api_compat/dask/array/_info.py:378:17 error[no-matching-overload] No overload of bound method `MutableMapping.update` matches arguments

zulip (https://github.com/zulip/zulip)
- zerver/views/auth.py:379:30 error[no-matching-overload] No overload of `dict.__init__` matches arguments

Full report with detailed diff (timing results)

AlexWaygood · 2026-04-26T23:46:14Z

(I suppose it wouldn't be sound for open TypedDicts?)

Indeed it wouldn't haha

charliermarsh · 2026-04-27T00:17:58Z

It looks like there are some false positives from cases in which we're relying on the inferred rather than the annotated type, e.g.:

forecast_entry: dict[str, Any] = dict(_forecast_entry)

We then treat entries in this dict as object rather than Any, which leads to downstream errors.

carljm · 2026-04-27T00:28:26Z

It looks like there are some false positives from cases in which we're relying on the inferred rather than the annotated type

That'll be fixed by the PR I'm working on for astral-sh/ty#136

charliermarsh · 2026-04-27T00:34:31Z

Figured as much, thanks!

carljm

Hmm, I am not totally convinced that special-casing is the right way out here, though maybe in the end it will be. (Especially since IIRC we have other diffs in the pipeline that do special-cased handling of even more dict(...) signatures?)

The normal (non-special-cased) inference path for dict.__init__ matches a single positional argument against the SupportsKeysAndGetItem protocol, and infers key and value types from that. It looks like if we completed our TypedDict __getitem__ overloads with a final overload for (str) -> object (which is technically correct for a non-closed TypedDict -- but would mean we no longer error on subscripting a non-closed TypedDict with unexpected key names, unless we added a special-cased rule to check for that) then the SupportsKeysAndGetIem assignability check would infer the right types here.

Throwing this into the playground or multiplay might clarify what I mean:

from typing import TypedDict, Iterable, Literal, overload

class TD(TypedDict):
    x: int
    y: str
    
class ManualBad:
    def keys(self) -> Iterable[str]: ...
    @overload
    def __getitem__(self, key: Literal["x"]) -> int: ...
    @overload
    def __getitem__(self, key: Literal["y"]) -> str: ...
    def __getitem__(self, key: str) -> object: ...
    
class Manual:
    def keys(self) -> Iterable[str]: ...
    @overload
    def __getitem__(self, key: Literal["x"]) -> int: ...
    @overload
    def __getitem__(self, key: Literal["y"]) -> str: ...
    @overload
    def __getitem__(self, key: str) -> object: ...
    def __getitem__(self, key: str) -> object: ...
    
def takes_dict(value: dict[str, object]) -> None: ...
def takes_kwargs(**kwargs: object) -> None: ...
def _(data: TD, bad: ManualBad, man: Manual):
    reveal_type(dict(bad))
    takes_dict(dict(bad))
    
    reveal_type(dict(man))
    takes_dict(dict(man))
    
    reveal_type(data.__getitem__)
    reveal_type(dict(data))
    takes_dict(dict(data))

carljm · 2026-04-27T00:51:46Z

+
+        // Probe silently so non-TypedDict arguments fall back to normal call binding without
+        // duplicate diagnostics; merge the inference only after accepting the fast path.
+        let mut speculative_builder = self.speculate();


Previously I think we've always used speculative building when we really need to infer the same thing with different type contexts. I don't love starting down this slope of using it not because we need different type context, but just because it's too much of a pain to reorganize things to avoid double-inference. It's not super likely, but certainly possible, that someone wraps dict(...) around a sizable expression that's actually costly to double infer.

charliermarsh · 2026-04-27T02:19:33Z

Your summary makes sense to me, and I pushed up the change, but I haven't reviewed the ecosystem diff yet.

charliermarsh · 2026-04-27T14:43:35Z

One downside (?) is that movie.__getitem__(key) where key: str no longer emits a diagnostic even if key isn't a valid key, but that does match Pyright.

We do still emit a diagnostic when subscripting with invalid keys via this special case.

carljm

Looks great, thank you!

## Summary Given: ```python from typing import TypedDict class TD(TypedDict): x: int y: str def _(data: TD): reveal_type(dict(data)) ``` We now reveal `dict[str, object]`. We could consider using a narrower value type (e.g., infer `dict[str, int]` if all values are `int`), though Mypy and Pyright don't do that (I suppose it wouldn't be sound for open TypedDicts?). Closes astral-sh/ty#3340.

astral-sh-bot Bot added the ty Multi-file analysis & type inference label Apr 26, 2026

charliermarsh marked this pull request as ready for review April 27, 2026 00:17

charliermarsh requested review from AlexWaygood, carljm, dcreager, ibraheemdev and sharkdp as code owners April 27, 2026 00:18

astral-sh-bot Bot assigned dcreager Apr 27, 2026

carljm reviewed Apr 27, 2026

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charliermarsh force-pushed the charlie/dict-obj branch from ccfa5cb to f9eb452 Compare April 27, 2026 14:02

charliermarsh marked this pull request as ready for review April 27, 2026 14:39

charliermarsh assigned carljm and unassigned dcreager Apr 27, 2026

charliermarsh force-pushed the charlie/dict-obj branch from f9eb452 to 0ece324 Compare April 27, 2026 19:25

charliermarsh mentioned this pull request Apr 27, 2026

[ty] Infer dict(**TypedDict) in TypedDict context #24709

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charliermarsh force-pushed the charlie/dict-obj branch 2 times, most recently from e1e39d6 to fd52ddf Compare May 1, 2026 00:07

charliermarsh force-pushed the charlie/dict-obj branch from fd52ddf to 7f73cbd Compare May 12, 2026 00:11

sharifhsn mentioned this pull request May 14, 2026

Pair type with swapped K V Generic variables is reported as Pair[Never, Never] astral-sh/ty#2817

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charliermarsh force-pushed the charlie/dict-obj branch from 7f73cbd to 4f8606b Compare May 21, 2026 08:40

charliermarsh marked this pull request as draft May 21, 2026 11:46

charliermarsh added 3 commits May 21, 2026 12:47

[ty] Infer dict(TypedDict) as dict[str, object]

ac78e54

add __getitem__

eaed4ec

Preserve after narrowing

d66424f

charliermarsh force-pushed the charlie/dict-obj branch 2 times, most recently from 13122b1 to b985e26 Compare May 21, 2026 11:52

Remove special-casing

f1fcc45

charliermarsh force-pushed the charlie/dict-obj branch from b985e26 to f1fcc45 Compare May 21, 2026 11:56

charliermarsh marked this pull request as ready for review May 21, 2026 12:00

astral-sh-bot Bot requested a review from carljm May 21, 2026 12:00

carljm approved these changes May 21, 2026

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charliermarsh merged commit 425d4f0 into main May 21, 2026
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charliermarsh deleted the charlie/dict-obj branch May 21, 2026 14:24

denyszhak mentioned this pull request Jun 1, 2026

Performance regression dict(value) on union of TypedDicts astral-sh/ty#3521

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