[red-knot] Add support for assert_never
#17287
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sharkdp
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Apr 7, 2025
| @@ -682,7 +682,7 @@ declare_lint! { | |||
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| declare_lint! { | |||
| /// ## What it does | |||
| /// Checks for `assert_type()` calls where the actual type | |||
| /// Checks for `assert_type()` and `assert_never()` calls where the actual type | |||
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I did consider making more changes in the lint description here. I also considered a dedicated new diagnostic. But eventually thought that this might be enough? Let me know if you have a different opinion.
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* origin/main: [red-knot] Default `python-platform` to current platform (#17183) [red-knot] Add new 'unreachable code' test case (#17306) [red-knot] mypy_primer: Run on `async-utils` (#17303) [red-knot] Add custom `__setattr__` support (#16748) [red-knot] Add `__init__` arguments check when doing `try_call` on a class literal (#16512) [`flake8-pie`] Avoid false positive for multiple assignment with `auto()` (`PIE796`) (#17274) [syntax-errors] Async comprehension in sync comprehension (#17177) [`airflow`] Expand module path check to individual symbols (`AIR302`) (#17278) [syntax-errors] Check annotations in annotated assignments (#17283) [syntax-errors] Extend annotation checks to `await` (#17282) [red-knot] Add support for `assert_never` (#17287) [`flake8-pytest-style`] Avoid false positive for legacy form of `pytest.raises` (`PT011`) (#17231) [red-knot] Do not show types for literal expressions on hover (#17290) [red-knot] Fix dead-code clippy warning (#17291) [red-knot] Reachability analysis (#17199) [red-knot] Don't use latency-sensitive for handlers (#17227)
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Summary
We already have partial "support" for
assert_never, because it is annotated asin typeshed. So we already emit a
invalid-argument-typediagnostic if the argument type toassert_neveris not assignable toNever.That is not enough, however. Gradual types like
Any,Unknown,@Todo(…)orAny & intcan be assignable toNever. Which means that we didn't issue any diagnostic in those cases.Also, it seems like
assert_neverdeserves a dedicated diagnostic message, not just a generic "invalid argument type" error.Test Plan
New Markdown tests.