Try to fix llvm#83802

clang/include/clang/AST/Decl.h

@@ -4335,15 +4335,15 @@ class FileScopeAsmDecl : public Decl {
 ///
 /// \note This is used in libInterpreter, clang -cc1 -fincremental-extensions
 /// and in tools such as clang-repl.
-class TopLevelStmtDecl : public Decl {
+class TopLevelStmtDecl : public Decl, public DeclContext {
   friend class ASTDeclReader;
   friend class ASTDeclWriter;
 
   Stmt *Statement = nullptr;
   bool IsSemiMissing = false;
 
   TopLevelStmtDecl(DeclContext *DC, SourceLocation L, Stmt *S)
-      : Decl(TopLevelStmt, DC, L), Statement(S) {}
+    : Decl(TopLevelStmt, DC, L), DeclContext(TopLevelStmt), Statement(S) {}
 
   virtual void anchor();
 
@@ -4354,15 +4354,19 @@ class TopLevelStmtDecl : public Decl {
   SourceRange getSourceRange() const override LLVM_READONLY;
   Stmt *getStmt() { return Statement; }
   const Stmt *getStmt() const { return Statement; }
-  void setStmt(Stmt *S) {
-    assert(IsSemiMissing && "Operation supported for printing values only!");
-    Statement = S;
-  }
+  void setStmt(Stmt *S);
   bool isSemiMissing() const { return IsSemiMissing; }
   void setSemiMissing(bool Missing = true) { IsSemiMissing = Missing; }
 
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
   static bool classofKind(Kind K) { return K == TopLevelStmt; }
+
+  static DeclContext *castToDeclContext(const TopLevelStmtDecl *D) {
+    return static_cast<DeclContext *>(const_cast<TopLevelStmtDecl*>(D));
+  }
+  static TopLevelStmtDecl *castFromDeclContext(const DeclContext *DC) {
+    return static_cast<TopLevelStmtDecl *>(const_cast<DeclContext*>(DC));
+  }
 };
 
 /// Represents a block literal declaration, which is like an

clang/include/clang/AST/DeclBase.h

@@ -2005,6 +2005,7 @@ class DeclContext {
     case Decl::Block:
     case Decl::Captured:
     case Decl::ObjCMethod:
+    case Decl::TopLevelStmt:
       return true;
     default:
       return getDeclKind() >= Decl::firstFunction &&

clang/include/clang/Basic/DeclNodes.td

@@ -95,7 +95,7 @@ def LinkageSpec : DeclNode<Decl>, DeclContext;
 def Export : DeclNode<Decl>, DeclContext;
 def ObjCPropertyImpl : DeclNode<Decl>;
 def FileScopeAsm : DeclNode<Decl>;
-def TopLevelStmt : DeclNode<Decl>;
+def TopLevelStmt : DeclNode<Decl>, DeclContext;
 def AccessSpec : DeclNode<Decl>;
 def Friend : DeclNode<Decl>;
 def FriendTemplate : DeclNode<Decl>;

clang/include/clang/Sema/Sema.h

@@ -3171,7 +3171,8 @@ class Sema final {
                               SourceLocation AsmLoc,
                               SourceLocation RParenLoc);
 
-  Decl *ActOnTopLevelStmtDecl(Stmt *Statement);
+  TopLevelStmtDecl *ActOnStartTopLevelStmtDecl(Scope *S);
+  void ActOnFinishTopLevelStmtDecl(TopLevelStmtDecl* D, Stmt *Statement);
 
   /// Handle a C++11 empty-declaration and attribute-declaration.
   Decl *ActOnEmptyDeclaration(Scope *S, const ParsedAttributesView &AttrList,

clang/lib/AST/Decl.cpp

@@ -5404,14 +5404,13 @@ FileScopeAsmDecl *FileScopeAsmDecl::CreateDeserialized(ASTContext &C,
 void TopLevelStmtDecl::anchor() {}
 
 TopLevelStmtDecl *TopLevelStmtDecl::Create(ASTContext &C, Stmt *Statement) {
-  assert(Statement);
   assert(C.getLangOpts().IncrementalExtensions &&
          "Must be used only in incremental mode");
 
-  SourceLocation BeginLoc = Statement->getBeginLoc();
+  SourceLocation Loc = Statement ? Statement->getBeginLoc() : SourceLocation();
   DeclContext *DC = C.getTranslationUnitDecl();
 
-  return new (C, DC) TopLevelStmtDecl(DC, BeginLoc, Statement);
+  return new (C, DC) TopLevelStmtDecl(DC, Loc, Statement);
 }
 
 TopLevelStmtDecl *TopLevelStmtDecl::CreateDeserialized(ASTContext &C,
@@ -5424,6 +5423,12 @@ SourceRange TopLevelStmtDecl::getSourceRange() const {
   return SourceRange(getLocation(), Statement->getEndLoc());
 }
 
+void TopLevelStmtDecl::setStmt(Stmt *S) {
+  assert(S);
+  Statement = S;
+  setLocation(Statement->getBeginLoc());
+}
+
 void EmptyDecl::anchor() {}
 
 EmptyDecl *EmptyDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L) {

clang/lib/AST/DeclBase.cpp

@@ -1301,6 +1301,7 @@ DeclContext *DeclContext::getPrimaryContext() {
   case Decl::ExternCContext:
   case Decl::LinkageSpec:
   case Decl::Export:
+  case Decl::TopLevelStmt:
   case Decl::Block:
   case Decl::Captured:
   case Decl::OMPDeclareReduction:

clang/lib/Parse/ParseDecl.cpp

@@ -5488,24 +5488,32 @@ Parser::DeclGroupPtrTy Parser::ParseTopLevelStmtDecl() {
   // Parse a top-level-stmt.
   Parser::StmtVector Stmts;
   ParsedStmtContext SubStmtCtx = ParsedStmtContext();
-  Actions.PushFunctionScope();
+  ParseScope FnScope(this, Scope::FnScope | Scope::DeclScope |
+                     Scope::CompoundStmtScope);
+  TopLevelStmtDecl *TLSD = Actions.ActOnStartTopLevelStmtDecl(getCurScope());
   StmtResult R = ParseStatementOrDeclaration(Stmts, SubStmtCtx);
-  Actions.PopFunctionScopeInfo();
   if (!R.isUsable())
     return nullptr;
 
-  SmallVector<Decl *, 2> DeclsInGroup;
-  DeclsInGroup.push_back(Actions.ActOnTopLevelStmtDecl(R.get()));
+  Actions.ActOnFinishTopLevelStmtDecl(TLSD, R.get());
 
   if (Tok.is(tok::annot_repl_input_end) &&
       Tok.getAnnotationValue() != nullptr) {
     ConsumeAnnotationToken();
-    cast<TopLevelStmtDecl>(DeclsInGroup.back())->setSemiMissing();
+    TLSD->setSemiMissing();
   }
 
-  // Currently happens for things like  -fms-extensions and use `__if_exists`.
-  for (Stmt *S : Stmts)
-    DeclsInGroup.push_back(Actions.ActOnTopLevelStmtDecl(S));
+  SmallVector<Decl *, 2> DeclsInGroup;
+  DeclsInGroup.push_back(TLSD);
+
+  // Currently happens for things like -fms-extensions and use `__if_exists`.
+  for (Stmt *S : Stmts) {
+    // Here we should be safe as `__if_exists` and friends are not introducing
+    // new variables which need to live outside file scope.
+    TopLevelStmtDecl *D = Actions.ActOnStartTopLevelStmtDecl(getCurScope());
+    Actions.ActOnFinishTopLevelStmtDecl(D, S);
+    DeclsInGroup.push_back(D);
+  }
 
   return Actions.BuildDeclaratorGroup(DeclsInGroup);
 }

clang/lib/Sema/SemaDecl.cpp

@@ -19949,12 +19949,21 @@ Decl *Sema::ActOnFileScopeAsmDecl(Expr *expr,
   return New;
 }
 
-Decl *Sema::ActOnTopLevelStmtDecl(Stmt *Statement) {
-  auto *New = TopLevelStmtDecl::Create(Context, Statement);
-  Context.getTranslationUnitDecl()->addDecl(New);
+TopLevelStmtDecl *Sema::ActOnStartTopLevelStmtDecl(Scope *S) {
+  auto *New = TopLevelStmtDecl::Create(Context, /*Statement=*/nullptr);
+  PushFunctionScope();
+  ActOnStartOfCompoundStmt(/*IsStmtExpr=*/false);
+  PushDeclContext(S, New);
   return New;
 }
 
+void Sema::ActOnFinishTopLevelStmtDecl(TopLevelStmtDecl* D, Stmt *Statement) {
+  D->setStmt(Statement);
+  PopDeclContext();
+  ActOnFinishOfCompoundStmt();
+  PopFunctionScopeInfo();
+}
+
 void Sema::ActOnPragmaRedefineExtname(IdentifierInfo* Name,
                                       IdentifierInfo* AliasName,
                                       SourceLocation PragmaLoc,

clang/test/Interpreter/execute-stmts.cpp

@@ -41,3 +41,13 @@ for (; i > 4; --i) { printf("i = %d\n", i); };
 
 int j = i; printf("j = %d\n", j);
 // CHECK-NEXT: j = 4
+
+for(int i=0; i<2; i+=1) {};
+
+for(int i=0; i<2; i+=1) ;
+
+int a = 2;
+for(int i=0; i<2; i+=1) a-=1;
+
+int *aa=nullptr;
+if (auto *b=aa) *b += 1;