From 933900debd513062a733b318b3e337ff177a1bcd Mon Sep 17 00:00:00 2001
From: Haled Odat <8566042+HalidOdat@users.noreply.github.com>
Date: Wed, 27 Sep 2023 21:18:45 +0200
Subject: [PATCH] Allow optimizing with destructuring

---
 boa_engine/src/bytecompiler/declarations.rs   | 33 ++++++++++++-------
 boa_engine/src/bytecompiler/statement/loop.rs |  9 ++++-
 2 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/boa_engine/src/bytecompiler/declarations.rs b/boa_engine/src/bytecompiler/declarations.rs
index 450e1d31712..95a43da0d92 100644
--- a/boa_engine/src/bytecompiler/declarations.rs
+++ b/boa_engine/src/bytecompiler/declarations.rs
@@ -5,7 +5,7 @@ use crate::{
         create_function_object_fast, create_generator_function_object, BindingOpcode,
         CodeBlockFlags, Opcode,
     },
-    JsNativeError, JsResult,
+    JsNativeError, JsResult, JsString,
 };
 use boa_ast::{
     declaration::{Binding, LexicalDeclaration, VariableList},
@@ -848,6 +848,16 @@ impl ByteCompiler<'_, '_> {
         strict: bool,
         generator: bool,
     ) -> (Option<Label>, bool) {
+        println!(
+            "Name: {}",
+            std::convert::Into::<JsString>::into(
+                self.context
+                    .interner()
+                    .resolve_expect(self.function_name)
+                    .utf16()
+            )
+            .to_std_string_escaped()
+        );
         let mut env_label = None;
         let mut additional_env = false;
 
@@ -957,7 +967,13 @@ impl ByteCompiler<'_, '_> {
         // NOTE(HalidOdat): Has been moved up, so "arguments" gets registed as
         //     the first binding in the environment with index 0.
         if arguments_object_needed {
-            let function_environment_index = self.function_environment_index.take();
+            if !strict {
+                self.can_optimize_local_variables = false;
+            }
+
+            let can_optimize_local_variables = self.can_optimize_local_variables;
+            self.can_optimize_local_variables = false;
+
             // Note: This happens at runtime.
             // a. If strict is true or simpleParameterList is false, then
             //     i. Let ao be CreateUnmappedArgumentsObject(argumentsList).
@@ -980,16 +996,9 @@ impl ByteCompiler<'_, '_> {
                 self.create_mutable_binding(arguments, false);
             }
 
-            if self.can_optimize_local_variables {
-                let binding = self.get_binding_value(arguments);
-                self.get_or_insert_binding(binding);
-            }
-
-            if !strict {
-                self.can_optimize_local_variables = false;
-            }
-
-            self.function_environment_index = function_environment_index;
+            let binding = self.get_binding_value(arguments);
+            self.get_or_insert_binding(binding);
+            self.can_optimize_local_variables = can_optimize_local_variables;
 
             self.code_block_flags |= CodeBlockFlags::NEEDS_ARGUMENTS_OBJECT;
         }
diff --git a/boa_engine/src/bytecompiler/statement/loop.rs b/boa_engine/src/bytecompiler/statement/loop.rs
index 6d00971c003..aac68aaff24 100644
--- a/boa_engine/src/bytecompiler/statement/loop.rs
+++ b/boa_engine/src/bytecompiler/statement/loop.rs
@@ -23,6 +23,7 @@ impl ByteCompiler<'_, '_> {
     ) {
         let mut let_binding_indices = None;
         let mut env_labels = None;
+        let mut env_labels_optimized_out = false;
         let mut iteration_env_labels = None;
 
         if let Some(init) = for_loop.init() {
@@ -33,7 +34,9 @@ impl ByteCompiler<'_, '_> {
                 }
                 ForLoopInitializer::Lexical(decl) => {
                     self.push_compile_environment(false);
-                    if !self.can_optimize_local_variables {
+                    if self.can_optimize_local_variables {
+                        env_labels_optimized_out = true;
+                    } else {
                         env_labels =
                             Some(self.emit_opcode_with_operand(Opcode::PushDeclarativeEnvironment));
                     }
@@ -128,6 +131,10 @@ impl ByteCompiler<'_, '_> {
             self.emit_opcode(Opcode::PopEnvironment);
         }
 
+        if env_labels_optimized_out {
+            self.pop_compile_environment();
+        }
+
         if let Some(env_labels) = env_labels {
             let env_index = self.pop_compile_environment();
             self.patch_jump_with_target(env_labels, env_index);