From ce634957c1bd25fdcc39c4e0321bcdf1cc332d60 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sat, 13 May 2023 18:53:14 +0200
Subject: [PATCH] LibJS/Bytecode: Restore old environments when an exception is
 caught

Unwind contexts now remember the lexical and variable environments in
effect when they were created. If an exception is caught, we revert
to those environments in the running execution context.
---
 Userland/Libraries/LibJS/Bytecode/BasicBlock.h    | 4 ++++
 Userland/Libraries/LibJS/Bytecode/Interpreter.cpp | 9 ++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Userland/Libraries/LibJS/Bytecode/BasicBlock.h b/Userland/Libraries/LibJS/Bytecode/BasicBlock.h
index 76533d67d5..fe046434a5 100644
--- a/Userland/Libraries/LibJS/Bytecode/BasicBlock.h
+++ b/Userland/Libraries/LibJS/Bytecode/BasicBlock.h
@@ -9,6 +9,7 @@
 #include <AK/Badge.h>
 #include <AK/DeprecatedString.h>
 #include <LibJS/Forward.h>
+#include <LibJS/Heap/Handle.h>
 
 namespace JS::Bytecode {
 
@@ -16,6 +17,9 @@ struct UnwindInfo {
     Executable const* executable;
     BasicBlock const* handler;
     BasicBlock const* finalizer;
+
+    Handle<Environment> lexical_environment;
+    Handle<Environment> variable_environment;
 };
 
 class BasicBlock {
diff --git a/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp b/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
index 44d21b75bf..c6dfb3aa48 100644
--- a/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
+++ b/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
@@ -91,6 +91,8 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Executable const& e
                 if (unwind_context.executable != m_current_executable)
                     break;
                 if (unwind_context.handler) {
+                    vm().running_execution_context().lexical_environment = unwind_context.lexical_environment;
+                    vm().running_execution_context().variable_environment = unwind_context.variable_environment;
                     m_current_block = unwind_context.handler;
                     unwind_context.handler = nullptr;
 
@@ -205,7 +207,12 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Executable const& e
 
 void Interpreter::enter_unwind_context(Optional<Label> handler_target, Optional<Label> finalizer_target)
 {
-    unwind_contexts().empend(m_current_executable, handler_target.has_value() ? &handler_target->block() : nullptr, finalizer_target.has_value() ? &finalizer_target->block() : nullptr);
+    unwind_contexts().empend(
+        m_current_executable,
+        handler_target.has_value() ? &handler_target->block() : nullptr,
+        finalizer_target.has_value() ? &finalizer_target->block() : nullptr,
+        vm().running_execution_context().lexical_environment,
+        vm().running_execution_context().variable_environment);
 }
 
 void Interpreter::leave_unwind_context()