[Macros] Improve visitation of auxiliary decls

Use the same pattern as 'getAllMembers()'. This supports nested macro
expansion:
```
std::function<void(Decl *)> visit;
visit = [&](Decl *d) {
  doIt(d);
  d->visitAuxiliaryDecls(visit);
};
for (auto *d : decls)
  visit(d);
```

Don't visit auxiliary decls in `PrintAST::visit(Decl *)` this function
is only intended for single decl printing. The caller should visit them
separately. For that, add
`ModuleDecl::getTopLevelDeclsWithAuxiliaryDecls()`

Author: rintaro

include/swift/AST/Module.h

@@ -967,6 +967,10 @@ class ModuleDecl
   /// The order of the results is not guaranteed to be meaningful.
   void getTopLevelDecls(SmallVectorImpl<Decl*> &Results) const;
 
+  /// Finds all top-level decls of this module including auxiliary decls.
+  void
+  getTopLevelDeclsWithAuxiliaryDecls(SmallVectorImpl<Decl *> &Results) const;
+
   void getExportedPrespecializations(SmallVectorImpl<Decl *> &results) const;
 
   /// Finds top-level decls of this module filtered by their attributes.

lib/AST/ASTPrinter.cpp

@@ -1035,12 +1035,6 @@ class PrintAST : public ASTVisitor<PrintAST> {
         Options.TransformContext->isPrintingSynthesizedExtension() &&
         isa<ExtensionDecl>(D);
 
-    SWIFT_DEFER {
-      D->visitAuxiliaryDecls([&](Decl *auxDecl) {
-        visit(auxDecl);
-      });
-    };
-
     if (!shouldPrint(D, true) && !Synthesize)
       return false;
 
@@ -4510,13 +4504,20 @@ bool PrintAST::printASTNodes(const ArrayRef<ASTNode> &Elements,
                              bool NeedIndent) {
   IndentRAII IndentMore(*this, NeedIndent);
   bool PrintedSomething = false;
+
+  std::function<void(Decl *)> printDecl;
+  printDecl = [&](Decl *d) {
+    if (d->shouldPrintInContext(Options))
+      visit(d);
+    d->visitAuxiliaryDecls(printDecl);
+  };
+
   for (auto element : Elements) {
     PrintedSomething = true;
     Printer.printNewline();
     indent();
     if (auto decl = element.dyn_cast<Decl*>()) {
-      if (decl->shouldPrintInContext(Options))
-        visit(decl);
+      printDecl(decl);
     } else if (auto stmt = element.dyn_cast<Stmt*>()) {
       visit(stmt);
     } else {

lib/AST/Module.cpp

@@ -1331,6 +1331,11 @@ void ModuleDecl::getTopLevelDecls(SmallVectorImpl<Decl*> &Results) const {
   FORWARD(getTopLevelDecls, (Results));
 }
 
+void ModuleDecl::getTopLevelDeclsWithAuxiliaryDecls(
+    SmallVectorImpl<Decl *> &Results) const {
+  FORWARD(getTopLevelDeclsWithAuxiliaryDecls, (Results));
+}
+
 void ModuleDecl::dumpDisplayDecls() const {
   SmallVector<Decl *, 32> Decls;
   getDisplayDecls(Decls);
@@ -3095,7 +3100,9 @@ void SourceFile::print(raw_ostream &OS, const PrintOptions &PO) {
 void SourceFile::print(ASTPrinter &Printer, const PrintOptions &PO) {
   std::set<DeclKind> MajorDeclKinds = {DeclKind::Class, DeclKind::Enum,
     DeclKind::Extension, DeclKind::Protocol, DeclKind::Struct};
-  for (auto decl : getTopLevelDecls()) {
+  SmallVector<Decl *> topLevelDecls;
+  getTopLevelDeclsWithAuxiliaryDecls(topLevelDecls);
+  for (auto decl : topLevelDecls) {
     if (!decl->shouldPrintInContext(PO))
       continue;
     // For a major decl, we print an empty line before it.
@@ -4190,14 +4197,18 @@ void FileUnit::getTopLevelDeclsWhereAttributesMatch(
 
 void FileUnit::getTopLevelDeclsWithAuxiliaryDecls(
     SmallVectorImpl<Decl*> &results) const {
+
+  std::function<void(Decl *)> addResult;
+  addResult = [&](Decl *decl) {
+    results.push_back(decl);
+    decl->visitAuxiliaryDecls(addResult);
+  };
+
   SmallVector<Decl *, 32> nonExpandedDecls;
   nonExpandedDecls.reserve(results.capacity());
   getTopLevelDecls(nonExpandedDecls);
   for (auto *decl : nonExpandedDecls) {
-    decl->visitAuxiliaryDecls([&](Decl *auxDecl) {
-      results.push_back(auxDecl);
-    });
-    results.push_back(decl);
+    addResult(decl);
   }
 }
 

lib/AST/NameLookup.cpp

@@ -4005,16 +4005,12 @@ void FindLocalVal::visitBraceStmt(BraceStmt *S, bool isTopLevelCode) {
     }
   }
 
-  auto visitDecl = [&](Decl *D) {
+  std::function<void(Decl *)> visitDecl;
+  visitDecl = [&](Decl *D) {
     if (auto *VD = dyn_cast<ValueDecl>(D))
       checkValueDecl(VD, DeclVisibilityKind::LocalVariable);
-    D->visitAuxiliaryDecls([&](Decl *D) {
-      if (auto *VD = dyn_cast<ValueDecl>(D))
-        checkValueDecl(VD, DeclVisibilityKind::LocalVariable);
-      // FIXME: Recursively call `visitDecl` to handle nested macros.
-    });
+    D->visitAuxiliaryDecls(visitDecl);
   };
-
   for (auto elem : S->getElements()) {
     if (auto *E = elem.dyn_cast<Expr *>()) {
       // 'MacroExpansionExpr' at code-item position may introduce value decls.

lib/Frontend/ModuleInterfaceSupport.cpp

@@ -833,7 +833,7 @@ bool swift::emitSwiftInterface(raw_ostream &out,
   InheritedProtocolCollector::PerTypeMap inheritedProtocolMap;
 
   SmallVector<Decl *, 16> topLevelDecls;
-  M->getTopLevelDecls(topLevelDecls);
+  M->getTopLevelDeclsWithAuxiliaryDecls(topLevelDecls);
   for (const Decl *D : topLevelDecls) {
     InheritedProtocolCollector::collectProtocols(inheritedProtocolMap, D);