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## Summary `ty` does not understand that calls to functions which have been annotated as having a return type of `Never` / `NoReturn` are terminal. This PR fixes that, by adding new reachability constraints when call expressions are seen. If the call expression evaluates to `Never`, the code following it will be considered to be unreachable. Note that, for adding these constraints, we only consider call expressions at the statement level, and that too only inside function scopes. This is because otherwise, the number of such constraints becomes too high, and evaluating them later on during type inference results in a major performance degradation. Fixes https://github.com/astral-sh/ty/issues/180 ## Test Plan New mdtests. ## Ecosystem changes This PR removes the following false-positives: - "Function can implicitly return `None`, which is not assignable to ...". - "Name `foo` used when possibly not defind" - because the branch in which it is not defined has a `NoReturn` call, or when `foo` was imported in a `try`, and the except had a `NoReturn` call. --------- Co-authored-by: David Peter <mail@david-peter.de> |
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| assert_never.md | ||
| assert_type.md | ||
| cast.md | ||