diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -4220,7 +4220,7 @@
   using field_range = llvm::iterator_range<specific_decl_iterator<FieldDecl>>;
 
   field_range fields() const { return field_range(field_begin(), field_end()); }
-  field_iterator field_begin() const;
+  virtual field_iterator field_begin() const;
 
   field_iterator field_end() const {
     return field_iterator(decl_iterator());
diff --git a/clang/include/clang/AST/DeclCXX.h b/clang/include/clang/AST/DeclCXX.h
--- a/clang/include/clang/AST/DeclCXX.h
+++ b/clang/include/clang/AST/DeclCXX.h
@@ -554,6 +554,11 @@
 
   bool hasDefinition() const { return DefinitionData || dataPtr(); }
 
+  RecordDecl::field_iterator field_begin() const override {
+    assert(hasDefinition() && "Definition not available to get fields.");
+    return static_cast<const RecordDecl *>(getDefinition())->field_begin();
+  }
+
   static CXXRecordDecl *Create(const ASTContext &C, TagKind TK, DeclContext *DC,
                                SourceLocation StartLoc, SourceLocation IdLoc,
                                IdentifierInfo *Id,