Short-circuit NoReturn analysis for Any or Unknown calls - #11419
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| if (isUnion(type)) { | ||
| return type.priv.subtypes.every((subtype) => { | ||
| callback(subtype); | ||
| return callback(subtype); |
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every expects the return result from callback
| const subtypeLiteralTypeName = getLiteralTypeClassName(subtype); | ||
| if (!subtypeLiteralTypeName) { | ||
| foundMismatch = true; | ||
| return undefined; |
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use early exit
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🔒 Automated review in progress — Rich Chiodo (@rchiodo) is auto-reviewing this PR. |
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Verification: The relevant tests could not be fully run in the isolated environment; this review is not fully verified. |
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Approved via Review Center.
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Document that a union call target containing Any or Unknown does not make subsequent code unreachable.
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Stop scanning a callable union once Any or Unknown proves the call cannot be guaranteed to return NoReturn.
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
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Summary
AnyorUnknown.NoReturn | UnknownandNoReturn | Anycall targets.Why the early exit is correct
A call is considered
NoReturnonly when every possible call-target subtype is known not to return normally.AnyandUnknowncan represent aNoReturncallable, but they can also represent a callable that returns normally. They therefore provide insufficient information to prove that the call does not return.This is also equivalent to the previous counting implementation. Each subtype increments
subtypeCount, but anAnyorUnknownsubtype matches none of the cases that incrementnoReturnTypeCount. Once one is encountered,noReturnTypeCount === subtypeCountcannot be true, even if every remaining subtype isNoReturn. Returningfalseimmediately preserves the existing reachability result while avoiding unnecessary analysis of later union members.Any reproducible mypy_primer diagnostic differences should be reviewed for correctness rather than treated as regressions solely because diagnostics changed.
The separate
typeUtilshelper optimization remains in #11681.Validation
pnpm --dir packages/pyright-internal exec jest typeEvaluator1.test -t "Unreachable1" --forceExitpnpm --dir packages/pyright-internal run buildpnpm exec prettier --check packages/pyright-internal/src/analyzer/codeFlowEngine.ts