Throwing variant for call sites whose invariant says tp must be list-shaped (e.g. the caller has just asserted isPairListConversion, or it's converting from a SumBuiltinList-shaped source). Silent getOrElse(SIRType.Data.tp) masks the bug — the wrong elem type then drives downstream conversions in the wrong shape.
Throwing variant for call sites whose invariant says tp must be list-shaped (e.g. the caller has just asserted isPairListConversion, or it's converting from a SumBuiltinList-shaped source). Silent getOrElse(SIRType.Data.tp) masks the bug — the wrong elem type then drives downstream conversions in the wrong shape.