Merge pull request #41626 from nkcsgexi/experiment-final-in-isPotentiallyOverridable

Author: nkcsgexi

include/swift/AST/Decl.h

@@ -1003,12 +1003,10 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
   /// deployment target.
   bool isWeakImported(ModuleDecl *fromModule) const;
 
-  /// Returns true if the nature of this declaration allows overrides.
-  /// Note that this does not consider whether it is final or whether
-  /// the class it's on is final.
+  /// Returns true if the nature of this declaration allows overrides syntactically.
   ///
   /// If this returns true, the decl can be safely casted to ValueDecl.
-  bool isPotentiallyOverridable() const;
+  bool isSyntacticallyOverridable() const;
 
   /// Retrieve the global actor attribute that applies to this declaration,
   /// if any.
@@ -7935,13 +7933,16 @@ inline unsigned ValueDecl::getNumCurryLevels() const {
   return curryLevels;
 }
 
-inline bool Decl::isPotentiallyOverridable() const {
+inline bool Decl::isSyntacticallyOverridable() const {
   if (isa<VarDecl>(this) ||
       isa<SubscriptDecl>(this) ||
       isa<FuncDecl>(this) ||
       isa<DestructorDecl>(this)) {
+    if (static_cast<const ValueDecl*>(this)->isFinal()) {
+      return false;
+    }
     auto classDecl = getDeclContext()->getSelfClassDecl();
-    return classDecl && !classDecl->isActor();
+    return classDecl && !classDecl->isActor() && !classDecl->isFinal();
   } else {
     return false;
   }

lib/AST/ASTVerifier.cpp

@@ -2314,7 +2314,7 @@ class Verifier : public ASTWalker {
 
       if (VD->hasAccess()) {
         if (VD->getFormalAccess() == AccessLevel::Open) {
-          if (!isa<ClassDecl>(VD) && !VD->isPotentiallyOverridable()) {
+          if (!isa<ClassDecl>(VD) && !VD->isSyntacticallyOverridable()) {
             Out << "decl cannot be 'open'\n";
             VD->dump(Out);
             abort();

lib/AST/Decl.cpp

@@ -3439,7 +3439,7 @@ static AccessLevel getMaximallyOpenAccessFor(const ValueDecl *decl) {
 
   // Non-final overridable class members are considered open to
   // @testable importers.
-  } else if (decl->isPotentiallyOverridable()) {
+  } else if (decl->isSyntacticallyOverridable()) {
     if (!cast<ValueDecl>(decl)->isSemanticallyFinal())
       return AccessLevel::Open;
   }
@@ -3793,7 +3793,7 @@ void ValueDecl::copyFormalAccessFrom(const ValueDecl *source,
     access = AccessLevel::FilePrivate;
 
   // Only certain declarations can be 'open'.
-  if (access == AccessLevel::Open && !isPotentiallyOverridable()) {
+  if (access == AccessLevel::Open && !isSyntacticallyOverridable()) {
     assert(!isa<ClassDecl>(this) &&
            "copying 'open' onto a class has complications");
     access = AccessLevel::Public;

lib/Sema/TypeCheckAttr.cpp

@@ -940,7 +940,7 @@ void AttributeChecker::visitAccessControlAttr(AccessControlAttr *attr) {
   if (attr->getAccess() == AccessLevel::Open) {
     auto classDecl = dyn_cast<ClassDecl>(D);
     if (!(classDecl && !classDecl->isActor()) &&
-        !D->isPotentiallyOverridable() &&
+        !D->isSyntacticallyOverridable() &&
         !attr->isInvalid()) {
       diagnose(attr->getLocation(), diag::access_control_open_bad_decl)
         .fixItReplace(attr->getRange(), "public");
@@ -3496,7 +3496,7 @@ void AttributeChecker::checkBackDeployAttrs(ArrayRef<BackDeployAttr *> Attrs) {
       continue;
 
     // Back deployment isn't compatible with dynamic dispatch.
-    if (VD->isPotentiallyOverridable() && !VD->isFinal()) {
+    if (VD->isSyntacticallyOverridable()) {
       diagnose(Attr->getLocation(), diag::attr_incompatible_with_non_final,
                Attr, D->getDescriptiveKind());
       continue;

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -2543,7 +2543,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
 
         for (auto *member : superclass->getMembers()) {
           if (auto *vd = dyn_cast<ValueDecl>(member)) {
-            if (vd->isPotentiallyOverridable()) {
+            if (vd->isSyntacticallyOverridable()) {
               (void) vd->isObjC();
             }
           }