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

[charliermarsh]

Summary

Given, e.g., def f() -> TD: return dict(**src), we now infer dict(**src) as matching TD if src is TD, for example. So the following are accepted, whereas on main they all produce diagnostics:

from typing import TypedDict

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

src: TD = {
    "x": 1,
    "y": "foo",
}

x: TD = dict(**src)

def f() -> TD: return dict(**src)

[astral-sh-bot]

Typing conformance results

No changes detected ✅

Current numbers

The percentage of diagnostics emitted that were expected errors held steady at 88.70%. The percentage of expected errors that received a diagnostic held steady at 84.63%. The number of fully passing files held steady at 84/134.

[astral-sh-bot]

Memory usage report

Memory usage unchanged ✅

[astral-sh-bot]

ecosystem-analyzer results

No diagnostic changes detected ✅

Flaky changes detected. This PR summary excludes flaky changes; see the HTML report for details.

Full report with detailed diff (timing results)

[codspeed-hq]

Merging this PR will not alter performance

✅ 53 untouched benchmarks
⏩ 60 skipped benchmarks¹

---

_{Comparing charlie/unpack-dict (bb3fc91) with main (5a74b37)}

Footnotes

1. 60 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[sharkdp]

The upstream issue says "This showed up in hydpy in the ecosystem report on #24653 …". Should we expect any hydpy ecosystem changes on this PR?

Also, the PR descriptions says "So the following are accepted […]", but I still get two errors for that snippet on this branch? (I guess it only works if src is annotated as TD?

[sharkdp]

Thank you.

[sharkdp]

Can you explain these two checks here? No tests fail when I remove them.

There is one test that looks like it's testing something similar (maybe_td), but it does not fail when I remove these. Neither does any other test.

Is the intent to cover something like this?

def _(unknown) -> None:
    td_unknown: TD = dict(**unknown)

If so, isn't there a more principled check that we could perform here instead? Like

Suggested change

	keyword_ty.is_dynamic()
	|| keyword_ty.is_never()
	keyword_ty
	.is_assignable_to(speculative_builder.db(), Type::TypedDict(typed_dict))