Return index from SwitchValueInst::getUniqueCaseForDestination

Author: meg-gupta

include/swift/SIL/SILInstruction.h

@@ -10224,7 +10224,7 @@ class SwitchValueInst final
   std::optional<unsigned> getUniqueCaseForDestination(SILBasicBlock *bb) const {
     for (unsigned i = 0; i < getNumCases(); ++i) {
       if (getCase(i).second == bb) {
-        return i + 1;
+        return i;
       }
     }
     return std::nullopt;

lib/SILOptimizer/Mandatory/YieldOnceCheck.cpp

@@ -496,7 +496,7 @@ class YieldOnceCheck : public SILFunctionTransform {
             switchValue->getUniqueCaseForDestination(noYieldTarget);
         assert(caseNumberOpt.has_value());
 
-        auto caseNumber = caseNumberOpt.value();
+        auto caseNumber = caseNumberOpt.value() + 1;
         diagnose(
             astCtx, enumCaseLoc, diag::switch_value_case_doesnt_yield,
             (Twine(caseNumber) + llvm::getOrdinalSuffix(caseNumber)).str());