Use Never instead of None for stores

[charliermarsh]

Summary

See: #13981 (comment)

[charliermarsh]

I'm having trouble tracing this -- where is this diagnostic even coming from today?

[dhruvmanila]

What's the issue? Is this failing? I think that's probably coming from infer_starred_expression

[charliermarsh]

The diagnostic is no longer showing up, so I had to remove these assertions along with the TODOs to remove them (?).

[dhruvmanila]

Yeah, I think that's correct. The diagnostics shouldn't be present in these cases and I think I left out one TODO in this specific case which might've confused you (?). The reason these diagnostics were showing up in the first place is because red knot tries to infer the starred expression (*b) but that isn't supported yet, before this PR it would've returned None and then it would raise a "not-an-iterable" diagnostic. But, it's now changed to use Never in this PR.

ruff/crates/red_knot_python_semantic/src/types/infer.rs

Lines 2341 to 2344 in c6b8215

	let iterable_ty = self.infer_expression(value);
	iterable_ty
	.iterate(self.db)
	.unwrap_with_diagnostic(value.as_ref().into(), self);

[carljm]

This PR shouldn't even affect this case (we should never use the type of a Store-context expression), but it does just because we don't support assigning to Starred yet, and the way the temporary code works out, it does currently try to iterate the inferred type of a Store-context expression. But not throwing the error is better, so if anything switching from None to Never is an improvement here.

[github-actions]

ruff-ecosystem results

Linter (stable)

ℹ️ ecosystem check encountered linter errors. (no lint changes; 1 project error)

pandas-dev/pandas (+0 -0 violations, +0 -0 fixes)

pypa/setuptools (error)

ruff failed
  Cause: Failed to parse /home/runner/work/ruff/ruff/checkouts/pypa:setuptools/ruff.toml
  Cause: TOML parse error at line 1, column 11
  |
1 | include = "pyproject.toml"
  |           ^^^^^^^^^^^^^^^^
invalid type: string "pyproject.toml", expected a sequence

Linter (preview)

ℹ️ ecosystem check encountered linter errors. (no lint changes; 1 project error)

pypa/setuptools (error)

ruff check --no-cache --exit-zero --ignore RUF9 --output-format concise --preview

ruff failed
  Cause: Failed to parse /home/runner/work/ruff/ruff/checkouts/pypa:setuptools/ruff.toml
  Cause: TOML parse error at line 1, column 11
  |
1 | include = "pyproject.toml"
  |           ^^^^^^^^^^^^^^^^
invalid type: string "pyproject.toml", expected a sequence

[carljm]

This PR shouldn't even affect this case (we should never use the type of a Store-context expression), but it does just because we don't support assigning to Starred yet, and the way the temporary code works out, it does currently try to iterate the inferred type of a Store-context expression. But not throwing the error is better, so if anything switching from None to Never is an improvement here.