[flang] Fix crash: ENTRY with generic interface of the same name

[klausler]

Summary

Name resolution was crashing while processing the ENTRY statement
due to a lack of special-case code necessary to handle the indirection
needed when the generic has the same name as the ENTRY.

[jeanPerier]

LGTM

flang/lib/Semantics/resolve-names.cpp

if (!HandlePreviousCalls(name, *extant, subpFlag)) {
         Say2(name, "'%s' is already defined as a global identifier"_err_en_US,
             *extant, "Previous definition of '%s'"_en_US);
       } else {
         SayAlreadyDeclared(name, *extant);
       }
       return;
     }
   }
-  Symbol &entrySymbol{MakeSymbol(outer, name.source, attrs)};
-  entrySymbol.set_details(std::move(entryDetails));
-  SetBindNameOn(entrySymbol);
-  entrySymbol.set(subpFlag);
-  Resolve(name, entrySymbol);
+
+  Symbol *entrySymbol{&MakeSymbol(outer, name.source, attrs)};
+  if (auto *generic{entrySymbol->detailsIf<GenericDetails>()}) {
+    CHECK(generic->specific());
+    entrySymbol = generic->specific();
+  }
+  entrySymbol->set_details(std::move(entryDetails));
+  SetBindNameOn(*entrySymbol);
+  entrySymbol->set(subpFlag);
+  Resolve(name, *entrySymbol);
 }
 
 // A subprogram declared with MODULE PROCEDURE
 bool SubprogramVisitor::BeginMpSubprogram(const parser::Name &name) {
   auto *symbol{FindSymbol(name)};
   if (symbol && symbol->has<SubprogramNameDetails>()) {
     symbol = FindSymbol(currScope().parent(), name);
   }
void SubprogramVisitor::EndSubprogram() {
   if (IsFunction(currScope())) {
     funcInfoStack_.pop_back();
   }
   PopScope();
 }
 
 bool SubprogramVisitor::HandlePreviousCalls(
     const parser::Name &name, Symbol &symbol, Symbol::Flag subpFlag) {
-  if (const auto *proc{symbol.detailsIf<ProcEntityDetails>()}; proc &&
+  // If the extant symbol is a generic, check its homonymous specific
+  // procedure instead if it has one.
+  if (auto *generic{symbol.detailsIf<GenericDetails>()}) {
+    return generic->specific() &&
+        HandlePreviousCalls(name, *generic->specific(), subpFlag);
+  } else if (const auto *proc{symbol.detailsIf<ProcEntityDetails>()}; proc &&
              !proc->isDummy() &&
              !symbol.attrs().HasAny(Attrs{Attr::INTRINSIC, Attr::POINTER})) {
     // There's a symbol created for previous calls to this subprogram or
     // ENTRY's name.  We have to replace that symbol in situ to avoid the
     // obligation to rewrite symbol pointers in the parse tree.
     if (!symbol.test(subpFlag)) {
       Say2(name,
           subpFlag == Symbol::Flag::Function
               ? "'%s' was previously called as a subroutine"_err_en_US
               : "'%s' was previously called as a function"_err_en_US,
bool ResolveNames(
   return !context.AnyFatalError();
 }
 
 // Processes a module (but not internal) function when it is referenced
 // in a specification expression in a sibling procedure.
 void ResolveSpecificationParts(
     SemanticsContext &context, const Symbol &subprogram) {
   auto originalLocation{context.location()};
+  ImplicitRulesMap implicitRulesMap;
+  bool localImplicitRulesMap{false};
+  if (!sharedImplicitRulesMap) {
+    sharedImplicitRulesMap = &implicitRulesMap;
+    localImplicitRulesMap = true;
+  }
   ResolveNamesVisitor visitor{
-      context, DEREF(sharedImplicitRulesMap), context.globalScope()};
+      context, *sharedImplicitRulesMap, context.globalScope()};
   const auto &details{subprogram.get<SubprogramNameDetails>()};
   ProgramTree &node{details.node()};
   const Scope &moduleScope{subprogram.owner()};
+  if (localImplicitRulesMap) {
+    visitor.BeginScope(const_cast<Scope &>(moduleScope));
+  } else {
     visitor.SetScope(const_cast<Scope &>(moduleScope));
+  }
   visitor.ResolveSpecificationParts(node);
   context.set_location(std::move(originalLocation));
+  if (localImplicitRulesMap) {
+    sharedImplicitRulesMap = nullptr;
+  }
 }
 
 } // namespace Fortran::semantics