[ty] Improve keyword argument narrowing for nested dictionaries

[ibraheemdev]

Fixes a bug in #23436 where nested dictionary literals are not tracked, e.g.,

def f(a: int, b: str): ...

x = {"inner": {"a": 1, "b": "a"}}
f(**x["inner"])

This is unlikely to have an ecosystem impact, but seems worth doing nonetheless.

[astral-sh-bot]

Typing conformance results

No changes detected ✅

Current numbers

The percentage of diagnostics emitted that were expected errors held steady at 85.29%. The percentage of expected errors that received a diagnostic held steady at 78.13%. The number of fully passing files held steady at 64/132.

[astral-sh-bot]

Memory usage report

Memory usage unchanged ✅

[astral-sh-bot]

ecosystem-analyzer results

Lint rule	Added	Removed	Changed
invalid-await	0	40	0
invalid-return-type	0	1	0
Total	0	41	0

Full report with detailed diff (timing results)

[carljm]

This change adds false negatives for direct assignments to nested keys:

def f(*, b: int): ...

x: dict[str, dict[str, int]] = {"a": {"b": 1}}
x["a"]["b"] = 1

# This should be an error: x has no top-level key "b".
f(**x)

This is correctly an error on main, but a false negative with this PR.

[ibraheemdev]

@carljm that example seems to error correctly on this PR?

➜  sandbox git:(ibraheem/dict-unpack-narrowing) ✗ cargo run --bin ty --manifest-path ~/dev/astral/ruff/Cargo.toml check main.py
error[invalid-argument-type]: Argument to function `f` is incorrect
  --> main.py:23:3
   |
22 | # This should be an error: x has no top-level key "b".
23 | f(**x)
   |   ^^^ Expected `int`, found `dict[str, int]`
   |
info: Function defined here
  --> main.py:17:5
   |
15 | #         self.mylist = [None, None, None]
16 |
17 | def f(*, b: int): ...
   |     ^    ------ Parameter declared here
18 |
19 | x: dict[str, dict[str, int]] = {"a": {"b": 1}}
   |
info: rule `invalid-argument-type` is enabled by default

Found 1 diagnostic

[carljm]

Weird, sorry! I'm sure I tested that... not sure what I did wrong. Maybe I had an earlier branch checked out by accident. Never mind!