[flang] Fix: use right symbol for parent component

When constructing the representation for a component reference
to an inherited component, expression semantics make the parent
component references explicit in the DataRef; e.g., base%component
becomes base%parent%grandparent%component if component was
inheritance-associated through two levels.  But expression semantics
was inserting references to the symbol table entries for the
intermediate types, not the symbols for the parent components in
the extended types.  (We didn't notice the distinction until
recently because both symbols have the same name; this only
affects lowering.)  Find and use the right symbols.

Differential Revision: https://reviews.llvm.org/D118746

Author: klausler

flang/include/flang/Semantics/symbol.h

@@ -665,6 +665,11 @@ class Symbol {
   // for a parameterized derived type instantiation with the instance's scope.
   const DerivedTypeSpec *GetParentTypeSpec(const Scope * = nullptr) const;
 
+  // If a derived type's symbol refers to an extended derived type,
+  // return the parent component's symbol.  The scope of the derived type
+  // can be overridden.
+  const Symbol *GetParentComponent(const Scope * = nullptr) const;
+
   SemanticsContext &GetSemanticsContext() const;
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
   LLVM_DUMP_METHOD void dump() const;
@@ -686,11 +691,6 @@ class Symbol {
   friend llvm::raw_ostream &DumpForUnparse(
       llvm::raw_ostream &, const Symbol &, bool);
 
-  // If a derived type's symbol refers to an extended derived type,
-  // return the parent component's symbol.  The scope of the derived type
-  // can be overridden.
-  const Symbol *GetParentComponent(const Scope * = nullptr) const;
-
   template <std::size_t> friend class Symbols;
   template <class, std::size_t> friend class std::array;
 };

flang/lib/Semantics/expression.cpp

@@ -987,11 +987,20 @@ std::optional<Component> ExpressionAnalyzer::CreateComponent(
   if (&component.owner() == &scope) {
     return Component{std::move(base), component};
   }
-  if (const semantics::Scope * parentScope{scope.GetDerivedTypeParent()}) {
-    if (const Symbol * parentComponent{parentScope->GetSymbol()}) {
-      return CreateComponent(
-          DataRef{Component{std::move(base), *parentComponent}}, component,
-          *parentScope);
+  if (const Symbol * typeSymbol{scope.GetSymbol()}) {
+    if (const Symbol *
+        parentComponent{typeSymbol->GetParentComponent(&scope)}) {
+      if (const auto *object{
+              parentComponent->detailsIf<semantics::ObjectEntityDetails>()}) {
+        if (const auto *parentType{object->type()}) {
+          if (const semantics::Scope *
+              parentScope{parentType->derivedTypeSpec().scope()}) {
+            return CreateComponent(
+                DataRef{Component{std::move(base), *parentComponent}},
+                component, *parentScope);
+          }
+        }
+      }
     }
   }
   return std::nullopt;