[flang][runtime] Handle array components in NAMELIST input

[klausler]

Summary

A namelist input item that is a derived type component reference
needs additional processing when the base item or the component
is an array. When both have rank > 0, the component reference
must of course be subscripted.

[PeteSteinfeld]

All builds and tests correctly and looks good.

Thanks for fixing this!

[klausler]

Back out a needless change that has led to local test breakage.

flang/runtime/namelist.cpp

static bool HandleComponent(IoStatementState &io, Descriptor &desc,
   IoErrorHandler &handler{io.GetIoErrorHandler()};
   char compName[nameBufferSize];
   if (GetLowerCaseName(io, compName, sizeof compName)) {
     const DescriptorAddendum *addendum{source.Addendum()};
     if (const typeInfo::DerivedType *
         type{addendum ? addendum->derivedType() : nullptr}) {
       if (const typeInfo::Component *
           comp{type->FindDataComponent(compName, std::strlen(compName))}) {
+        bool createdDesc{false};
+        if (comp->rank() > 0 && source.rank() > 0) {
+          // If base and component are both arrays, the component name
+          // must be followed by subscripts; process them now.
+          std::size_t byteCount{0};
+          if (std::optional<char32_t> next{io.GetNextNonBlank(byteCount)};
+              next && *next == '(') {
+            io.HandleRelativePosition(byteCount); // skip over '('
+            StaticDescriptor<maxRank, true, 16> staticDesc;
+            Descriptor &tmpDesc{staticDesc.descriptor()};
+            comp->CreatePointerDescriptor(tmpDesc, source, handler);
+            if (!HandleSubscripts(io, desc, tmpDesc, compName)) {
+              return false;
+            }
+            createdDesc = true;
+          }
+        }
+        if (!createdDesc) {
           comp->CreatePointerDescriptor(desc, source, handler);
+        }
+        if (source.rank() > 0) {
+          if (desc.rank() > 0) {
+            handler.SignalError(
+                "NAMELIST component reference '%%%s' of input group "
+                "item %s cannot be an array when its base is not scalar",
+                compName, name);
+            return false;
+          }
+          desc.raw().rank = source.rank();
+          for (int j{0}; j < source.rank(); ++j) {
+            const auto &srcDim{source.GetDimension(j)};
+            desc.GetDimension(j)
+                .SetBounds(1, srcDim.UpperBound())
+                .SetByteStride(srcDim.ByteStride());
+          }
+        }
         return true;
       } else {
         handler.SignalError(
             "NAMELIST component reference '%%%s' of input group item %s is not "
             "a component of its derived type",
             compName, name);
       }
     } else if (source.type().IsDerived()) {