[flang] Enforce rest of semantic constraint C919

[klausler]

Summary

A reference to an allocatable or pointer component must be applied
to a scalar base object. (This is the second part of constraint C919;
the first part is already checked.)

[PeteSteinfeld]

Looks great!

flang/include/flang/Semantics/expression.h

       const parser::SectionSubscript &);
   std::vector<Subscript> AnalyzeSectionSubscripts(
       const std::list<parser::SectionSubscript> &);
+  std::optional<Component> CreateComponent(
+      DataRef &&, const Symbol &, const semantics::Scope &);
   MaybeExpr Designate(DataRef &&);
   MaybeExpr CompleteSubscripts(ArrayRef &&);
   MaybeExpr ApplySubscripts(DataRef &&, std::vector<Subscript> &&);

flang/lib/Semantics/expression.cpp

       for (const auto &expr : ref.subscript()) {
         subscriptRank += expr.Rank();
       }
-      if (subscriptRank > 0) {
+      if (subscriptRank > 0) { // C919a
         Say("Subscripts of component '%s' of rank-%d derived type "
             "array have rank %d but must all be scalar"_err_en_US,
             symbol.name(), baseRank, subscriptRank);

     int componentRank{symbol.Rank()};
     if (componentRank > 0) {
       int baseRank{component->base().Rank()};
-      if (baseRank > 0) {
+      if (baseRank > 0) { // C919a
         Say("Reference to whole rank-%d component '%%%s' of "
             "rank-%d array of derived type is not allowed"_err_en_US,
             componentRank, symbol.name(), baseRank);

 }
 
 // Components of parent derived types are explicitly represented as such.
-static std::optional<Component> CreateComponent(
+std::optional<Component> ExpressionAnalyzer::CreateComponent(
     DataRef &&base, const Symbol &component, const semantics::Scope &scope) {
+  if (IsAllocatableOrPointer(component) && base.Rank() > 0) { // C919b
+    Say("An allocatable or pointer component reference must be applied to a scalar base"_err_en_US);
+  }
   if (&component.owner() == &scope) {
     return Component{std::move(base), component};
   }

flang/test/Semantics/deallocate01.f90

 
 Deallocate(z%p)
 
+!ERROR: An allocatable or pointer component reference must be applied to a scalar base
 Deallocate(x%p, stat=s, errmsg=e)
-Deallocate(x%p, errmsg=e)
-Deallocate(x%p, stat=s)
+Deallocate(x, errmsg=e)
+Deallocate(x, stat=s)
 
-Deallocate(y%p, stat=s, errmsg=e)
-Deallocate(y%p, errmsg=e)
-Deallocate(y%p, stat=s)
+Deallocate(y, stat=s, errmsg=e)
+Deallocate(y, errmsg=e)
+Deallocate(y, stat=s)
 
 Deallocate(z, stat=s, errmsg=e)
 Deallocate(z, errmsg=e)
 Deallocate(z, stat=s)
 
-Deallocate(z, y%p, stat=s, errmsg=e)
-Deallocate(z, y%p, errmsg=e)
-Deallocate(z, y%p, stat=s)
+Deallocate(z, y, stat=s, errmsg=e)
+Deallocate(z, y, errmsg=e)
+Deallocate(z, y, stat=s)
 
 End Program