Parameterize visitAuxiliaryDecls to account for separate traversal

Some places want to do in-order walks of MacroExpansionDecls, but still
visit auxiliary declarations. Rather than force them to specifically
filter out declarations from the MacroExpansionDecl, add a parameter to
visitAuxiliaryDecls to skip them.

Author: DougGregor

include/swift/AST/Decl.h

@@ -884,7 +884,13 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
   ///
   /// Auxiliary declarations can be property wrapper backing variables,
   /// backing variables for 'lazy' vars, or peer macro expansions.
-  void visitAuxiliaryDecls(AuxiliaryDeclCallback callback) const;
+  ///
+  /// When \p visitFreestandingExpanded is true (the default), this will also
+  /// visit the declarations produced by a freestanding macro expansion.
+  void visitAuxiliaryDecls(
+      AuxiliaryDeclCallback callback,
+      bool visitFreestandingExpanded = true
+  ) const;
 
   using MacroCallback = llvm::function_ref<void(CustomAttr *, MacroDecl *)>;
 

lib/AST/ASTWalker.cpp

@@ -455,7 +455,6 @@ class Traversal : public ASTVisitor<Traversal, Expr*, Stmt*,
       else
         return true;
     }
-    // Visit auxiliary decls, which may be decls from macro expansions.
     bool alreadyFailed = false;
     if (shouldWalkExpansion) {
       MED->forEachExpandedNode([&](ASTNode expandedNode) {

lib/AST/Decl.cpp

@@ -381,7 +381,10 @@ DeclAttributes Decl::getSemanticAttrs() const {
   return getAttrs();
 }
 
-void Decl::visitAuxiliaryDecls(AuxiliaryDeclCallback callback) const {
+void Decl::visitAuxiliaryDecls(
+    AuxiliaryDeclCallback callback,
+    bool visitFreestandingExpanded
+) const {
   auto &ctx = getASTContext();
   auto *mutableThis = const_cast<Decl *>(this);
   SourceManager &sourceMgr = ctx.SourceMgr;
@@ -414,13 +417,15 @@ void Decl::visitAuxiliaryDecls(AuxiliaryDeclCallback callback) const {
     }
   }
 
-  else if (auto *med = dyn_cast<MacroExpansionDecl>(mutableThis)) {
-    if (auto bufferID = evaluateOrDefault(
-            ctx.evaluator, ExpandMacroExpansionDeclRequest{med}, {})) {
-      auto startLoc = sourceMgr.getLocForBufferStart(*bufferID);
-      auto *sourceFile = moduleDecl->getSourceFileContainingLocation(startLoc);
-      for (auto *decl : sourceFile->getTopLevelDecls())
-        callback(decl);
+  if (visitFreestandingExpanded) {
+    if (auto *med = dyn_cast<MacroExpansionDecl>(mutableThis)) {
+      if (auto bufferID = evaluateOrDefault(
+              ctx.evaluator, ExpandMacroExpansionDeclRequest{med}, {})) {
+        auto startLoc = sourceMgr.getLocForBufferStart(*bufferID);
+        auto *sourceFile = moduleDecl->getSourceFileContainingLocation(startLoc);
+        for (auto *decl : sourceFile->getTopLevelDecls())
+          callback(decl);
+      }
     }
   }
 

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -1845,7 +1845,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     if (!isa<ClassDecl>(decl->getDeclContext())) {
       decl->visitAuxiliaryDecls([&](Decl *auxiliaryDecl) {
         this->visit(auxiliaryDecl);
-      });
+      }, /*visitFreestandingExpanded=*/false);
     }
 
     if (auto *Stats = getASTContext().Stats)
@@ -2062,10 +2062,6 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     // Assign a discriminator.
     (void)MED->getDiscriminator();
     MED->forEachExpandedNode([&](ASTNode node) {
-      // Decls in expansion already visited as auxiliary decls.
-      if (node.is<Decl *>())
-        return;
-
       TypeChecker::typeCheckASTNode(node, MED->getDeclContext());
     });
   }

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -299,18 +299,19 @@ public struct DefineDeclsWithKnownNamesMacro: DeclarationMacro {
   }
 }
 
-public struct VarDeclMacro: DeclarationMacro {
+public struct VarDeclMacro: CodeItemMacro {
   public static func expansion(
     of node: some FreestandingMacroExpansionSyntax,
     in context: some MacroExpansionContext
-  ) throws -> [DeclSyntax] {
+  ) throws -> [CodeBlockItemSyntax] {
+    let name = context.makeUniqueName("fromMacro")
     return [
+      "let \(name) = 23",
+      "use(\(name))",
       """
-      let fromMacro = 23
-      use(fromMacro)
       if true {
-        let fromMacro = "string"
-        use(fromMacro)
+        let \(name) = "string"
+        use(\(name))
       }
       """
     ]

test/Macros/macro_expand.swift

@@ -151,13 +151,6 @@ func testFileID(a: Int, b: Int) {
 
 testFileID(a: 1, b: 2)
 
-@freestanding(declaration, names: named(fromMacro)) macro varDecl() = #externalMacro(module: "MacroDefinition", type: "VarDeclMacro")
-
-func testVarDecl() {
-  func use<T>(_ t: T) {}
-  #varDecl()
-}
-
 @freestanding(expression) macro stringifyAndTry<T>(_ value: T) -> (T, String) =
     #externalMacro(module: "MacroDefinition", type: "StringifyAndTryMacro")
 

test/Macros/macro_expand_codeitems.swift

@@ -33,3 +33,10 @@ func testFreestandingMacroExpansion() {
   #codeItems
 }
 testFreestandingMacroExpansion()
+
+@freestanding(codeItem) macro varDecl() = #externalMacro(module: "MacroDefinition", type: "VarDeclMacro")
+
+func testVarDecl() {
+  func use<T>(_ t: T) {}
+  #varDecl()
+}

test/Macros/top_level_freestanding.swift

@@ -50,7 +50,7 @@ func lookupGlobalFreestandingExpansion() {
 
 #anonymousTypes(public: true) { "hello" }
 
-// CHECK-SIL: sil @$s9MacroUser03$s9A71User33_082AE7CFEFA6960C804A9FE7366EB5A0Ll14anonymousTypesfMf0_4namefMu_C5helloSSyF
+// CHECK-SIL: sil @$s9MacroUser03$s9A70User33_082AE7CFEFA6960C804A9FE7366EB5A0Ll14anonymousTypesfMf_4namefMu_C5helloSSyF
 
 @main
 struct Main {