From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marja=20H=C3=B6ltt=C3=A4?= <marja@chromium.org>
Date: Fri, 3 Sep 2021 11:46:26 +0200
Subject: Fix class variable redeclaration
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ParserBase::ParseClassLiteral and BaseConsumedPreparseData::RestoreDataForScope
both declare the class variable, but the logic is so complex
that they sometimes ended up both declaring it.

This is further complicated by some of the variable values (esp.
inner_scope_calls_eval_) potentially changing in between, so we can't
just redo the same logic any more.

Forcefully make it work by making RestoreDataForScope declare the variable
iff ParseClassLiteral didn't.

Bug: chromium:1245870
Change-Id: I777fd9d78145240448fc25709d2b118977d91056
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3140596
Commit-Queue: Marja Hölttä <marja@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76654}

diff --git a/src/parsing/preparse-data.cc b/src/parsing/preparse-data.cc
index 1643c6ba1a648e53f8b75bb9c910ed605ce82183..f368a11f9ab09c745feaffa8f406771bc3f858ea 100644
--- a/src/parsing/preparse-data.cc
+++ b/src/parsing/preparse-data.cc
@@ -666,12 +666,13 @@ void BaseConsumedPreparseData<Data>::RestoreDataForScope(
     scope->AsDeclarationScope()->RecordNeedsPrivateNameContextChainRecalc();
   }
   if (ShouldSaveClassVariableIndexField::decode(scope_data_flags)) {
-    Variable* var;
-    // An anonymous class whose class variable needs to be saved do not
+    Variable* var = scope->AsClassScope()->class_variable();
+    // An anonymous class whose class variable needs to be saved might not
     // have the class variable created during reparse since we skip parsing
     // the inner scopes that contain potential access to static private
     // methods. So create it now.
-    if (scope->AsClassScope()->is_anonymous_class()) {
+    if (var == nullptr) {
+      DCHECK(scope->AsClassScope()->is_anonymous_class());
       var = scope->AsClassScope()->DeclareClassVariable(
           ast_value_factory, nullptr, kNoSourcePosition);
       AstNodeFactory factory(ast_value_factory, zone);
@@ -679,9 +680,6 @@ void BaseConsumedPreparseData<Data>::RestoreDataForScope(
           factory.NewVariableDeclaration(kNoSourcePosition);
       scope->declarations()->Add(declaration);
       declaration->set_var(var);
-    } else {
-      var = scope->AsClassScope()->class_variable();
-      DCHECK_NOT_NULL(var);
     }
     var->set_is_used();
     var->ForceContextAllocation();
diff --git a/test/mjsunit/regress/regress-crbug-1245870.js b/test/mjsunit/regress/regress-crbug-1245870.js
new file mode 100644
index 0000000000000000000000000000000000000000..2ef3f753d500880717f10f26ed8cca4a47079196
--- /dev/null
+++ b/test/mjsunit/regress/regress-crbug-1245870.js
@@ -0,0 +1,14 @@
+// Copyright 2021 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.
+
+class Outer {
+  test() {
+    return class {
+      static #a() { }
+      b = eval();
+    };
+  }
+}
+const obj = new Outer();
+obj.test();
