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Fix exhaustive match checking for final class objects #11683

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Piyush Kulkarni (piy-ushk) wants to merge 4 commits into
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Fix exhaustive match checking for final class objects #11683

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9f9dd61
Fix exhaustive match checking for final class objects
piy-ushk Aug 27, 2026
c5499be
Address PR feedback: fix formatting and add regression test
piy-ushk Aug 27, 2026
460963d
Address PR feedback: add custom metaclass check for class matching
piy-ushk Aug 27, 2026
ad68a05
Address PR feedback: use lookUpClassMember to resolve __eq__ in metac…
piy-ushk Aug 27, 2026
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9 changes: 9 additions & 0 deletions packages/pyright-internal/src/analyzer/patternMatching.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1334,6 +1334,15 @@ function narrowTypeBasedOnValuePattern(
(subjectSubtypeExpanded) => {
// If this is a negative test, see if it's an enum value.
if (!isPositiveTest) {
if (
isInstantiableClass(subjectSubtypeExpanded) &&
isInstantiableClass(valueSubtypeExpanded) &&
isSameWithoutLiteralValue(subjectSubtypeExpanded, valueSubtypeExpanded)
) {
if (ClassType.isFinal(subjectSubtypeExpanded) || !subjectSubtypeExpanded.priv.includeSubclasses) {

@rchiodo Rich Chiodo (rchiodo) Aug 27, 2026

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Issue · Please address or respond

This condition exceeds the repository's enforced 120-character Prettier formatting limit. Please wrap the clauses before merging.

return undefined;
}
}

@rchiodo Rich Chiodo (rchiodo) Aug 27, 2026

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Warning · Non-blocking recommendation

Add regression coverage showing that a final class-object match is exhaustive and an equivalent non-final class remains non-exhaustive. This analyzer behavior change currently has no test specification.

if (
isClassInstance(subjectSubtypeExpanded) &&
isClassInstance(valueSubtypeExpanded) &&
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