[clang] Instantiate attributes on LabelDecls (llvm#115924)

Start propagating attributes on (e.g.) labels inside of templated
functions to their instances.

Author: ericastor

clang/include/clang/AST/ASTNodeTraverser.h

@@ -800,6 +800,13 @@ class ASTNodeTraverser
       Visit(A);
   }
 
+  void VisitLabelStmt(const LabelStmt *Node) {
+    if (Node->getDecl()->hasAttrs()) {
+      for (const auto *A : Node->getDecl()->getAttrs())
+        Visit(A);
+    }
+  }
+
   void VisitCXXCatchStmt(const CXXCatchStmt *Node) {
     Visit(Node->getExceptionDecl());
   }

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -990,6 +990,7 @@ Decl *
 TemplateDeclInstantiator::VisitLabelDecl(LabelDecl *D) {
   LabelDecl *Inst = LabelDecl::Create(SemaRef.Context, Owner, D->getLocation(),
                                       D->getIdentifier());
+  SemaRef.InstantiateAttrs(TemplateArgs, D, Inst, LateAttrs, StartingScope);
   Owner->addDecl(Inst);
   return Inst;
 }

clang/test/SemaCXX/attr-annotate-ast.cpp

@@ -0,0 +1,55 @@
+// RUN: %clang_cc1 -std=gnu++20 -fsyntax-only -ast-dump %s | FileCheck %s
+
+void f() {
+  [[clang::annotate("decl", 1)]] int i = 0;
+  [[clang::annotate("stmt", 2)]] i += 1;
+[[clang::annotate("label", 3)]] label1:
+  i += 2;
+}
+
+// CHECK: -FunctionDecl {{.*}} f 'void ()'
+// CHECK: -VarDecl {{.*}} used i 'int'
+// CHECK: -AnnotateAttr {{.*}} "decl"
+// CHECK: -IntegerLiteral {{.*}} 'int' 1
+// CHECK: -AttributedStmt
+// CHECK: -AnnotateAttr {{.*}} "stmt"
+// CHECK: -IntegerLiteral {{.*}} 'int' 2
+// CHECK: -LabelStmt {{.*}} 'label1'
+// CHECK: -AnnotateAttr {{.*}} "label"
+// CHECK: -IntegerLiteral {{.*}} 'int' 3
+// CHECK: -CompoundAssignOperator
+
+template <typename T> void g() {
+  [[clang::annotate("tmpl_decl", 4)]] T j = 0;
+  [[clang::annotate("tmpl_stmt", 5)]] j += 1;
+[[clang::annotate("tmpl_label", 6)]] label2:
+  j += 2;
+}
+
+// CHECK: -FunctionTemplateDecl {{.*}} g
+// CHECK: -VarDecl {{.*}} referenced j 'T'
+// CHECK: -AnnotateAttr {{.*}} "tmpl_decl"
+// CHECK: -IntegerLiteral {{.*}} 'int' 4
+// CHECK: -AttributedStmt
+// CHECK: -AnnotateAttr {{.*}} "tmpl_stmt"
+// CHECK: -IntegerLiteral {{.*}} 'int' 5
+// CHECK: -LabelStmt {{.*}} 'label2'
+// CHECK: -AnnotateAttr {{.*}} "tmpl_label"
+// CHECK: -IntegerLiteral {{.*}} 'int' 6
+// CHECK: -CompoundAssignOperator
+
+void h() {
+  g<int>();
+}
+
+// CHECK: -FunctionDecl {{.*}} used g 'void ()' implicit_instantiation
+// CHECK: -VarDecl {{.*}} used j 'int'
+// CHECK: -AnnotateAttr {{.*}} "tmpl_decl"
+// CHECK: -IntegerLiteral {{.*}} 'int' 4
+// CHECK: -AttributedStmt
+// CHECK: -AnnotateAttr {{.*}} Implicit "tmpl_stmt"
+// CHECK: -IntegerLiteral {{.*}} 'int' 5
+// CHECK: -LabelStmt {{.*}} 'label2'
+// CHECK: -AnnotateAttr {{.*}} "tmpl_label"
+// CHECK: -IntegerLiteral {{.*}} 'int' 6
+// CHECK: -CompoundAssignOperator