Only create ScopeInfos for scopes that really need one

src/ast/scopes.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/ast/scopes.h"
 
 #include <set>
 
 #include "src/accessors.h"
 #include "src/ast/ast.h"
@@ skipping 1028 matching lines @@
   ResolveVariablesRecursively(info);
   AllocateVariablesRecursively();
 
   MaybeHandle<ScopeInfo> outer_scope;
   for (const Scope* s = outer_scope_; s != nullptr; s = s->outer_scope_) {
     if (s->scope_info_.is_null()) continue;
     outer_scope = s->scope_info_;
     break;
   }
   AllocateScopeInfosRecursively(info->isolate(), mode, outer_scope);
+  // The debugger expects all shared function infos to contain a scope info.
+  // Since the top-most scope will end up in a shared function info, make sure
+  // it has one, even if it doesn't need a scope info.
+  // TODO(jochen|yangguo): Remove this requirement.
+  if (scope_info_.is_null()) {
+    scope_info_ = ScopeInfo::Create(info->isolate(), zone(), this, outer_scope);
+  }
 }
 
 bool Scope::AllowsLazyParsing() const {
   // If we are inside a block scope, we must parse eagerly to find out how
   // to allocate variables on the block scope. At this point, declarations may
   // not have yet been parsed.
   for (const Scope* s = this; s != nullptr; s = s->outer_scope_) {
     if (s->is_block_scope()) return false;
   }
   return true;
@@ skipping 747 matching lines @@
   Variable* function =
       is_function_scope() ? AsDeclarationScope()->function_var() : nullptr;
   bool is_function_var_in_context =
       function != nullptr && function->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS -
          (is_function_var_in_context ? 1 : 0);
 }
 
 }  // namespace internal
 }  // namespace v8