[flang] Restore checking for some optional values before use

[klausler]

Summary

Recent commits (2098ad7f00324ee0f2a6538f418a6f81dfdd2edb and
15a9a72ee68166c0cff3f036cacd3c82be66c729) replaced usage of "o.value()"
on optionals with "*o". Those optional values are expected to be
present, but now, if they're not, compilation will proceed with
garbage data rather than crashing on an uncaught exception.
Add asserts for presence to restore the previous level of safety.

[vzakhari]

LGTM

[klausler]

Update patch.

[jeanPerier]

flang/lib/Lower/ConvertExpr.cpp

3674

lhsLoad.has_value()

[klausler]

Incorporate Jean's suggested change.

[tschuett]

Are asserts the right solution or do you need control flow to check whether optionals have a value?

flang/include/flang/Evaluate/tools.h

 template <TypeCategory TOCAT, typename VALUE>
 common::IfNoLvalue<Expr<SomeKind<TOCAT>>, VALUE> ConvertToKind(
     int kind, VALUE &&x) {
-  return *common::SearchTypes(
-      ConvertToKindHelper<TOCAT, VALUE>{kind, std::move(x)});
+  auto result{common::SearchTypes(
+      ConvertToKindHelper<TOCAT, VALUE>{kind, std::move(x)})};
+  CHECK(result.has_value());
+  return *result;
 }
 
 // Given a type category CAT, SameKindExprs<CAT, N> is a variant that

flang/lib/Lower/Bridge.cpp

               } else {
                 llvm_unreachable("unknown category");
               }
-              if (lhsIsWholeAllocatable)
+              if (lhsIsWholeAllocatable) {
+                assert(lhsRealloc.has_value());
                 fir::factory::finalizeRealloc(*builder, loc, *lhsMutableBox,
                                               /*lbounds=*/std::nullopt,
                                               /*takeLboundsIfRealloc=*/false,
                                               *lhsRealloc);
+              }
             },
 
             // [2] User defined assignment. If the context is a scalar

flang/lib/Lower/ConvertCall.cpp

     callNumResults = call.getNumResults();
   }
 
-  if (caller.mustSaveResult())
+  if (caller.mustSaveResult()) {
+    assert(allocatedResult.has_value());
     builder.create<fir::SaveResultOp>(loc, callResult,
                                       fir::getBase(*allocatedResult),
                                       arrayResultShape, resultLengths);
+  }
 
   if (allocatedResult) {
     allocatedResult->match(

flang/lib/Lower/ConvertExpr.cpp

       mlir::Value oldInnerArg = modifyOp.getSequence();
       std::size_t offset = explicitSpace->argPosition(oldInnerArg);
       explicitSpace->setInnerArg(offset, fir::getBase(lexv));
-      fir::ExtendedValue exv = arrayModifyToExv(
-          builder, loc, *explicitSpace->getLhsLoad(0), modifyOp.getResult(0));
+      auto lhsLoad = explicitSpace->getLhsLoad(0);
+      assert(lhsLoad.has_value());
+      fir::ExtendedValue exv =
+          arrayModifyToExv(builder, loc, *lhsLoad, modifyOp.getResult(0));
       genScalarUserDefinedAssignmentCall(builder, loc, userAssignment, exv,
                                          elementalExv);
     } else {

     }
     mlir::Value val = builder.createConvert(loc, eleTy, origVal);
     if (isBoundsSpec()) {
+      assert(lbounds.has_value());
       auto lbs = *lbounds;
       if (lbs.size() > 0) {
         // Rebox the value with user-specified shift.

                                            mlir::Value{});
       }
     } else if (isBoundsRemap()) {
+      assert(lbounds.has_value());
       auto lbs = *lbounds;
       if (lbs.size() > 0) {
         // Rebox the value with user-specified shift and shape.
+        assert(ubounds.has_value());
         auto shapeShiftArgs = flatZip(lbs, *ubounds);
         auto shapeTy = fir::ShapeShiftType::get(eleTy.getContext(), lbs.size());
         mlir::Value shapeShift =

         charLen = builder.createTemporary(loc, builder.getI64Type());
         mlir::Value castLen =
             builder.createConvert(loc, builder.getI64Type(), fir::getLen(exv));
+        assert(charLen.has_value());
         builder.create<fir::StoreOp>(loc, castLen, *charLen);
       }
     }

 
     // Convert to extended value.
     if (fir::isa_char(seqTy.getEleTy())) {
+      assert(charLen.has_value());
       auto len = builder.create<fir::LoadOp>(loc, *charLen);
       return {fir::CharArrayBoxValue{mem, len, extents}, /*needCopy=*/false};
     }

flang/lib/Lower/ConvertExprToHLFIR.cpp

   gen(const Fortran::evaluate::FunctionRef<T> &expr) {
     mlir::Type resType =
         Fortran::lower::TypeBuilder<T>::genType(getConverter(), expr);
-    return *Fortran::lower::convertCallToHLFIR(
+    auto result = Fortran::lower::convertCallToHLFIR(
         getLoc(), getConverter(), expr, resType, getSymMap(), getStmtCtx());
+    assert(result.has_value());
+    return *result;
   }
 
   template <typename T>

flang/lib/Lower/CustomIntrinsicCall.cpp

   llvm::SmallVector<fir::ExtendedValue> args;
   args.push_back(getOperand(0));
   args.push_back(getOperand(1));
+  auto iPC = isPresentCheck(2);
+  assert(iPC.has_value());
   args.push_back(builder
-                     .genIfOp(loc, {resultType}, *isPresentCheck(2),
+                     .genIfOp(loc, {resultType}, *iPC,
                               /*withElseRegion=*/true)
                      .genThen([&]() {
                        fir::ExtendedValue sizeExv = getOperand(2);