From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Calvin Watford <cwatford@slack-corp.com>
Date: Wed, 17 Jul 2024 12:52:10 -0600
Subject: fix: disable scope reuse & associated dchecks

This change was introduced in https://crrev.com/c/5630974 which reuses
scope info objects across allocations. Unfortunately, this change seems
to be not yet fully cooked and causes crashes with normal usage of V8.

In particular, Node.js call's V8's `v8::ScriptCompiler::CompileFunction`
method. This ends up wrapping the source code in a function, which this
code is not yet prepared to handle. The generated function wrapper
(created by V8) has no source position, so it reports being at the start
of the source, which may overlap with other scopes that are in the
original source. This new feature adds a "UniqueIdInScript" concept that
is derived from the source position of a scope, along with the invariant
that inner scopes have a higher ID than outer scopes, which does not
hold for the above situation.

This patch is not intended to remain indefinitely. Once the upstream
feature stabilizes, we can remove this patch. Unfortunately, there is no
public tracking bug for this feature nor the crashes its been causing,
so we'll have to keep an eye on this for the time being.

diff --git a/src/ast/scopes.cc b/src/ast/scopes.cc
index e2b2405aaae8fb324ab12250fd3ee767fd3a7ce4..e83a8a4ffbc31ec1336d5bd289039f9ba31a3052 100644
--- a/src/ast/scopes.cc
+++ b/src/ast/scopes.cc
@@ -2713,9 +2713,9 @@ void Scope::AllocateScopeInfosRecursively(
 
   // Allocate ScopeInfos for inner scopes.
   for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
-    DCHECK_GT(scope->UniqueIdInScript(), UniqueIdInScript());
-    DCHECK_IMPLIES(scope->sibling_, scope->sibling_->UniqueIdInScript() !=
-                                        scope->UniqueIdInScript());
+    // DCHECK_GT(scope->UniqueIdInScript(), UniqueIdInScript());
+    // DCHECK_IMPLIES(scope->sibling_, scope->sibling_->UniqueIdInScript() !=
+    //                                     scope->UniqueIdInScript());
     if (!scope->is_function_scope() ||
         scope->AsDeclarationScope()->ShouldEagerCompile()) {
       scope->AllocateScopeInfosRecursively(isolate, next_outer_scope,
diff --git a/src/flags/flag-definitions.h b/src/flags/flag-definitions.h
index 98f060c2c0338b3abdc7f46740999c6d8645f65e..2f899c43a3296fac6a2c85111fa57e8b8c34a586 100644
--- a/src/flags/flag-definitions.h
+++ b/src/flags/flag-definitions.h
@@ -996,6 +996,8 @@ DEFINE_BOOL(trace_track_allocation_sites, false,
 DEFINE_BOOL(trace_migration, false, "trace object migration")
 DEFINE_BOOL(trace_generalization, false, "trace map generalization")
 
+// ELECTRON: The following flag should remain false by default until we can
+//   remove `fix_disable_scope_reuse_associated_dchecks.patch`
 DEFINE_BOOL(reuse_scope_infos, false,
             "reuse scope infos from previous compiles")