Repository navigation
Crash: Unhandled case in resolveStructuredTypeMembers when switching on an evolving [] array inside a loop #64813
Description
🔎 Search Terms
"Unhandled case in resolveStructuredTypeMembers"
🕗 Version & Regression Information
Commit:
9eedcb0dd7257f8a1a175adbef28f3b6d3492d7a (main, 2026-10-14); also aa8149273b23401f0a79a5f0384c42de51888693
Build configuration:
cd tsc && go build -o tsc ./cmd/tsc (GOWORK=off, GOTOOLCHAIN=auto -> go1.27.0)
Operating System:
Ubuntu 24.04.4 LTS (Docker image fusion-fuzz-typescript:latest), linux/amd64
⏯ Playground Link
No response
💻 Code
const a = [];
while (true) switch (a) { case 0: }🙁 Actual behavior
panic: Unhandled case in resolveStructuredTypeMembers [recovered, repanicked]
goroutine 313 [running]:
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).resolveStructuredTypeMembers(...)
tsc/internal/checker/checker.go:19531
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).isWeakType(...)
tsc/internal/checker/relater.go:681
github.com/microsoft/TypeScript/tsc/internal/checker.(*Relater).isRelatedToEx(...)
tsc/internal/checker/relater.go:2711
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).checkTypeRelatedToEx(...)
tsc/internal/checker/relater.go:370
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).isTypeRelatedTo(...)
tsc/internal/checker/relater.go:200
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).areTypesComparable(...)
tsc/internal/checker/relater.go:166
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).narrowTypeBySwitchOnDiscriminant.func1(...)
tsc/internal/checker/flow.go:1132
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).filterType(...)
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).narrowTypeBySwitchOnDiscriminant(...)
tsc/internal/checker/flow.go:1132
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).getTypeAtSwitchClause(...)
tsc/internal/checker/flow.go:1066
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).getTypeAtFlowNode(...)
tsc/internal/checker/flow.go:161
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).getTypeAtFlowLoopLabel(...)
tsc/internal/checker/flow.go:1370
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).getFlowTypeOfReferenceEx(...)
tsc/internal/checker/flow.go:98
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).checkIdentifier(...)
github.com/microsoft/TypeScript/tsc/internal/checker.(*Checker).checkSwitchStatement(...)
🙂 Expected behavior
no crash
Additional information about the issue
To reproduce: tsc ./min.ts
Activity