[flang] Accept FINAL forward reference to separate module procedure

[klausler]

Summary

When one of a derived type's FINAL procedures is in a submodule,
its separate module procedure interface must necessarily be a
forward reference from the FINAL statement, as its interface
could not appear before the definition of the type. The implementation
of FINAL procedure name resolution doesn't work for forward references;
replace it.

[klausler]

Ping!

[PeteSteinfeld]

All builds and tests correctly and looks good.

flang/lib/Semantics/resolve-names.cpp

public:
   void Post(const parser::ProcDecl &);
   bool Pre(const parser::TypeBoundProcedurePart &);
   void Post(const parser::TypeBoundProcedurePart &);
   void Post(const parser::ContainsStmt &);
   bool Pre(const parser::TypeBoundProcBinding &) { return BeginAttrs(); }
   void Post(const parser::TypeBoundProcBinding &) { EndAttrs(); }
   void Post(const parser::TypeBoundProcedureStmt::WithoutInterface &);
   void Post(const parser::TypeBoundProcedureStmt::WithInterface &);
-  void Post(const parser::FinalProcedureStmt &);
+  bool Pre(const parser::FinalProcedureStmt &);
   bool Pre(const parser::TypeBoundGenericStmt &);
   bool Pre(const parser::StructureDef &); // returns false
   bool Pre(const parser::Union::UnionStmt &);
   bool Pre(const parser::StructureField &);
   void Post(const parser::StructureField &);
   bool Pre(const parser::AllocateStmt &);
   void Post(const parser::AllocateStmt &);
   bool Pre(const parser::StructureConstructor &);
for (auto &bindingName : x.bindingNames) {
         if (!GetAttrs().test(Attr::DEFERRED)) {
           context().SetError(*s);
         }
       }
     }
   }
 }
 
-void DeclarationVisitor::Post(const parser::FinalProcedureStmt &x) {
+bool DeclarationVisitor::Pre(const parser::FinalProcedureStmt &x) {
   if (currScope().IsDerivedType() && currScope().symbol()) {
     if (auto *details{currScope().symbol()->detailsIf<DerivedTypeDetails>()}) {
       for (const auto &subrName : x.v) {
-        if (const auto *name{ResolveName(subrName)}) {
-          auto pair{
-              details->finals().emplace(name->source, DEREF(name->symbol))};
-          if (!pair.second) { // C787
-            Say(name->source,
-                "FINAL subroutine '%s' already appeared in this derived type"_err_en_US,
-                name->source)
-                .Attach(pair.first->first,
-                    "earlier appearance of this FINAL subroutine"_en_US);
-          }
-        }
-      }
-    }
-  }
+        Symbol *symbol{FindSymbol(subrName)};
+        if (!symbol) {
+          // FINAL procedures must be module subroutines
+          symbol = &MakeSymbol(
+              currScope().parent(), subrName.source, Attrs{Attr::MODULE});
+          Resolve(subrName, symbol);
+          symbol->set_details(ProcEntityDetails{});
+          symbol->set(Symbol::Flag::Subroutine);
+        }
+        if (auto pair{details->finals().emplace(subrName.source, *symbol)};
+            !pair.second) { // C787
+          Say(subrName.source,
+              subrName.source)
+  return false;
 }
 
 bool DeclarationVisitor::Pre(const parser::TypeBoundGenericStmt &x) {
   const auto &accessSpec{std::get<std::optional<parser::AccessSpec>>(x.t)};
   const auto &genericSpec{std::get<Indirection<parser::GenericSpec>>(x.t)};
   const auto &bindingNames{std::get<std::list<parser::Name>>(x.t)};
   GenericSpecInfo info{genericSpec.value()};
   SourceName symbolName{info.symbolName()};
if (checkIndexUseInOwnBounds_ &&
           name.source);
     }
     return &name;
   }
   if (isImplicitNoneType() && !inDataStmtObject_) {
     Say(name, "No explicit type declared for '%s'"_err_en_US);
     return nullptr;
   }
-  // Create the symbol then ensure it is accessible
+  // Create the symbol, then ensure that it is accessible
   if (checkIndexUseInOwnBounds_ && *checkIndexUseInOwnBounds_ == name.source) {
     Say(name,
         "Implied DO index '%s' uses itself in its own bounds expressions"_err_en_US,
         name.source);
   }
   MakeSymbol(InclusiveScope(), name.source, Attrs{});
   auto *symbol{FindSymbol(name)};
   if (!symbol) {

flang/test/Semantics/symbol30.f90

+! RUN: %python %S/test_symbols.py %s %flang_fc1
+!DEF: /m Module
+module m
+ !DEF: /m/t PUBLIC DerivedType
+ type :: t
+ contains
+  !DEF: /m/forwardreferenced ELEMENTAL, IMPURE, MODULE, PUBLIC (Subroutine) Subprogram
+  final :: forwardreferenced
+ end type
+ interface
+  !REF: /m/forwardreferenced
+  !DEF: /m/forwardreferenced/this INTENT(INOUT) ObjectEntity TYPE(t)
+  impure elemental module subroutine forwardreferenced (this)
+   !REF: /m/t
+   !REF: /m/forwardreferenced/this
+   type(t), intent(inout) :: this
+  end subroutine
+ end interface
+end module