AST: Introduce Decl::getSemanticCustomAttrs().

In order to avoid triggering request cycles as `SemanticDeclAttrsRequest` grows
to cover a larger range of implicit attributes, we need a lighter-weight
accessor for just the CustomAttrs that have been expanded from macros.
Introduce `getSemanticCustomAttrs()` and adopt it where `getSemanticAttrs()`
had been previously used to enumerate macro expanded custom attributes.

Author: tshortli

include/swift/AST/Decl.h

@@ -924,7 +924,13 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
   /// expansions.
   OrigDeclAttributes getOriginalAttrs() const;
 
-  /// Returns the semantic attributes attached to this declaration,
+  /// Returns the semantic CustomAttrs attached to this declaration,
+  /// including attributes that are generated as the result of member
+  /// attribute macro expansion.
+  DeclAttributes::AttributeKindRange<CustomAttr, false>
+  getSemanticCustomAttrs() const;
+
+  /// Returns all semantic attributes attached to this declaration,
   /// including attributes that are generated as the result of member
   /// attribute macro expansion.
   DeclAttributes getSemanticAttrs() const;

lib/AST/Decl.cpp

@@ -375,6 +375,15 @@ OrigDeclAttributes Decl::getOriginalAttrs() const {
   return OrigDeclAttributes(getAttrs(), this);
 }
 
+DeclAttributes::AttributeKindRange<CustomAttr, false>
+Decl::getSemanticCustomAttrs() const {
+  auto mutableThis = const_cast<Decl *>(this);
+  (void)evaluateOrDefault(getASTContext().evaluator,
+                          ExpandMemberAttributeMacros{mutableThis}, {});
+
+  return getAttrs().getAttributes<CustomAttr>();
+}
+
 DeclAttributes Decl::getSemanticAttrs() const {
   (void)evaluateOrDefault(getASTContext().evaluator,
                           SemanticDeclAttrsRequest{this}, {});
@@ -438,7 +447,7 @@ void Decl::visitAuxiliaryDecls(
 
 void Decl::forEachAttachedMacro(MacroRole role,
                                 MacroCallback macroCallback) const {
-  for (auto customAttrConst : getSemanticAttrs().getAttributes<CustomAttr>()) {
+  for (auto customAttrConst : getSemanticCustomAttrs()) {
     auto customAttr = const_cast<CustomAttr *>(customAttrConst);
     auto *macroDecl = getResolvedMacro(customAttr);
 

lib/AST/NameLookup.cpp

@@ -1725,7 +1725,7 @@ void namelookup::forEachPotentialAttachedMacro(
   // We intentionally avoid calling `forEachAttachedMacro` in order to avoid
   // a request cycle.
   auto moduleScopeCtx = decl->getDeclContext()->getModuleScopeContext();
-  for (auto attrConst : decl->getSemanticAttrs().getAttributes<CustomAttr>()) {
+  for (auto attrConst : decl->getSemanticCustomAttrs()) {
     auto *attr = const_cast<CustomAttr *>(attrConst);
     UnresolvedMacroReference macroRef(attr);
     auto macroName = macroRef.getMacroName();

lib/Sema/TypeCheckAccess.cpp

@@ -1281,7 +1281,7 @@ class AccessControlChecker : public AccessControlCheckerBase,
   }
 
   void checkAttachedMacrosAccess(const Decl *D) {
-    for (auto customAttrC : D->getSemanticAttrs().getAttributes<CustomAttr>()) {
+    for (auto customAttrC : D->getSemanticCustomAttrs()) {
       auto customAttr = const_cast<CustomAttr *>(customAttrC);
       auto *macroDecl = D->getResolvedMacro(customAttr);
       if (macroDecl) {

lib/Sema/TypeCheckMacros.cpp

@@ -1664,7 +1664,7 @@ ArrayRef<unsigned>
 ExpandExtensionMacros::evaluate(Evaluator &evaluator,
                                 NominalTypeDecl *nominal) const {
   SmallVector<unsigned, 2> bufferIDs;
-  for (auto customAttrConst : nominal->getSemanticAttrs().getAttributes<CustomAttr>()) {
+  for (auto customAttrConst : nominal->getSemanticCustomAttrs()) {
     auto customAttr = const_cast<CustomAttr *>(customAttrConst);
     auto *macro = nominal->getResolvedMacro(customAttr);
 

lib/Sema/TypeCheckPropertyWrapper.cpp

@@ -438,8 +438,7 @@ AttachedPropertyWrappersRequest::evaluate(Evaluator &evaluator,
   auto dc = var->getDeclContext();
   llvm::TinyPtrVector<CustomAttr *> result;
 
-  auto attachedAttrs = var->getSemanticAttrs();
-  for (auto attr : attachedAttrs.getAttributes<CustomAttr>()) {
+  for (auto attr : var->getSemanticCustomAttrs()) {
     auto mutableAttr = const_cast<CustomAttr *>(attr);
     // Figure out which nominal declaration this custom attribute refers to.
     auto *nominal = evaluateOrDefault(
@@ -481,6 +480,9 @@ AttachedPropertyWrappersRequest::evaluate(Evaluator &evaluator,
       continue;
     }
 
+    // Note: Getting the semantic attrs here would trigger a request cycle.
+    auto attachedAttrs = var->getAttrs();
+
     // Check for conflicting attributes.
     if (attachedAttrs.hasAttribute<LazyAttr>() ||
         attachedAttrs.hasAttribute<NSCopyingAttr>() ||