From 9f4cc6435d8f7533641aac3951d4b4dd87649035 Mon Sep 17 00:00:00 2001
From: Luke Wilde <lukew@serenityos.org>
Date: Mon, 14 Mar 2022 02:26:39 +0000
Subject: [PATCH] LibJS/Bytecode: Unwind to closest unwind boundary on Throw

This will leave any lexical/variable environments on the way to the
closest unwind context boundary.

This will not leave the closest unwind context, as we still need the
unwind context to perform the Throw instruction correctly.
---
 Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp | 1 +
 Userland/Libraries/LibJS/Bytecode/Generator.h    | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp b/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
index cce2818b6b..2ccd183519 100644
--- a/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
+++ b/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
@@ -1441,6 +1441,7 @@ Bytecode::CodeGenerationErrorOr<void> UpdateExpression::generate_bytecode(Byteco
 Bytecode::CodeGenerationErrorOr<void> ThrowStatement::generate_bytecode(Bytecode::Generator& generator) const
 {
     TRY(m_argument->generate_bytecode(generator));
+    generator.perform_needed_unwinds<Bytecode::Op::Throw>();
     generator.emit<Bytecode::Op::Throw>();
     return {};
 }
diff --git a/Userland/Libraries/LibJS/Bytecode/Generator.h b/Userland/Libraries/LibJS/Bytecode/Generator.h
index 91662a9aea..6ebb9ad4a0 100644
--- a/Userland/Libraries/LibJS/Bytecode/Generator.h
+++ b/Userland/Libraries/LibJS/Bytecode/Generator.h
@@ -167,6 +167,8 @@ public:
         Optional<BlockBoundaryType> boundary_to_stop_at;
         if constexpr (IsSame<OpType, Bytecode::Op::Return> || IsSame<OpType, Bytecode::Op::Yield>)
             VERIFY(!is_break_node);
+        else if constexpr (IsSame<OpType, Bytecode::Op::Throw>)
+            boundary_to_stop_at = BlockBoundaryType::Unwind;
         else
             boundary_to_stop_at = is_break_node ? BlockBoundaryType::Break : BlockBoundaryType::Continue;