Add Variadic 'dropAttrs' (#78476)

As suggested in #78200

This adds a variadic 'dropAttrs', which drops all attributes of any of
the types specified.

Author: erichkeane

clang/include/clang/AST/DeclBase.h

@@ -548,17 +548,18 @@ class alignas(8) Decl {
     return hasAttrs() ? getAttrs().end() : nullptr;
   }
 
-  template <typename T>
-  void dropAttr() {
+  template <typename... Ts> void dropAttrs() {
     if (!HasAttrs) return;
 
     AttrVec &Vec = getAttrs();
-    llvm::erase_if(Vec, [](Attr *A) { return isa<T>(A); });
+    llvm::erase_if(Vec, [](Attr *A) { return isa<Ts...>(A); });
 
     if (Vec.empty())
       HasAttrs = false;
   }
 
+  template <typename T> void dropAttr() { dropAttrs<T>(); }
+
   template <typename T>
   llvm::iterator_range<specific_attr_iterator<T>> specific_attrs() const {
     return llvm::make_range(specific_attr_begin<T>(), specific_attr_end<T>());

clang/lib/Sema/SemaDecl.cpp

@@ -7068,8 +7068,7 @@ static void checkAttributesAfterMerging(Sema &S, NamedDecl &ND) {
   if (WeakRefAttr *Attr = ND.getAttr<WeakRefAttr>()) {
     if (ND.isExternallyVisible()) {
       S.Diag(Attr->getLocation(), diag::err_attribute_weakref_not_static);
-      ND.dropAttr<WeakRefAttr>();
-      ND.dropAttr<AliasAttr>();
+      ND.dropAttrs<WeakRefAttr, AliasAttr>();
     }
   }
 

clang/lib/Sema/SemaDeclCXX.cpp

@@ -6545,8 +6545,7 @@ void Sema::checkClassLevelDLLAttribute(CXXRecordDecl *Class) {
   if ((Context.getTargetInfo().getCXXABI().isMicrosoft() ||
        Context.getTargetInfo().getTriple().isPS()) &&
       (!Class->isExternallyVisible() && Class->hasExternalFormalLinkage())) {
-    Class->dropAttr<DLLExportAttr>();
-    Class->dropAttr<DLLImportAttr>();
+    Class->dropAttrs<DLLExportAttr, DLLImportAttr>();
     return;
   }
 

clang/lib/Sema/SemaTemplate.cpp

@@ -9229,10 +9229,8 @@ void Sema::CheckConceptRedefinition(ConceptDecl *NewDecl,
 /// that has just been explicitly specialized.
 static void StripImplicitInstantiation(NamedDecl *D, bool MinGW) {
   if (MinGW || (isa<FunctionDecl>(D) &&
-                cast<FunctionDecl>(D)->isFunctionTemplateSpecialization())) {
-    D->dropAttr<DLLImportAttr>();
-    D->dropAttr<DLLExportAttr>();
-  }
+                cast<FunctionDecl>(D)->isFunctionTemplateSpecialization()))
+    D->dropAttrs<DLLImportAttr, DLLExportAttr>();
 
   if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
     FD->setInlineSpecified(false);