David Peter 3a77768f79 [ty] Reachability constraints (#18621) ... ## Summary * Completely removes the concept of visibility constraints. Reachability constraints are now used to model the static visibility of bindings and declarations. Reachability constraints are *much* easier to reason about / work with, since they are applied at the beginning of a branch, and not applied retroactively. Removing the duplication between visibility and reachability constraints also leads to major code simplifications [^1]. For an overview of how the new constraint system works, see the updated doc comment in `reachability_constraints.rs`. * Fixes a [control-flow modeling bug (panic)](https://github.com/astral-sh/ty/issues/365) involving `break` statements in loops * Fixes a [bug where](https://github.com/astral-sh/ty/issues/624) where `elif` branches would have wrong reachability constraints * Fixes a [bug where](https://github.com/astral-sh/ty/issues/648) code after infinite loops would not be considered unreachble * Fixes a panic on the `pywin32` ecosystem project, which we should be able to move to `good.txt` once this has been merged. * Removes some false positives in unreachable code because we infer `Never` more often, due to the fact that reachability constraints now apply retroactively to *all* active bindings, not just to bindings inside a branch. * As one example, this removes the `division-by-zero` diagnostic from https://github.com/astral-sh/ty/issues/443 because we now infer `Never` for the divisor. * Supersedes and includes similar test changes as https://github.com/astral-sh/ruff/pull/18392 closes https://github.com/astral-sh/ty/issues/365 closes https://github.com/astral-sh/ty/issues/624 closes https://github.com/astral-sh/ty/issues/642 closes https://github.com/astral-sh/ty/issues/648 ## Benchmarks Benchmarks on black, pandas, and sympy showed that this is neither a performance improvement, nor a regression. ## Test Plan Regression tests for: - [x] https://github.com/astral-sh/ty/issues/365 - [x] https://github.com/astral-sh/ty/issues/624 - [x] https://github.com/astral-sh/ty/issues/642 - [x] https://github.com/astral-sh/ty/issues/648 [^1]: I'm afraid this is something that @carljm advocated for since the beginning, and I'm not sure anymore why we have never seriously tried this before. So I suggest we do *not* attempt to do a historical deep dive to find out exactly why this ever became so complicated, and just enjoy the fact that we eventually arrived here. --------- Co-authored-by: Carl Meyer <carl@astral.sh>		2025-06-17 09:24:28 +02:00
..
resources	[ty] Reachability constraints (#18621)	2025-06-17 09:24:28 +02:00
src	[ty] Reachability constraints (#18621)	2025-06-17 09:24:28 +02:00
tests	[ty] Use more parallelism when running corpus tests (#18711)	2025-06-16 17:38:55 +00:00
build.rs
Cargo.toml	[ty] Pull types on synthesized Python files created by mdtest (#18539)	2025-06-12 10:32:17 +01:00
mdtest.py
mdtest.py.lock