From 2c26ee89acd183770907e58e231d2bc8a125d0df Mon Sep 17 00:00:00 2001
From: davidot <davidot@serenityos.org>
Date: Sun, 27 Nov 2022 02:24:38 +0100
Subject: [PATCH] LibJS: Remove m_first_invalid_property_range from
 ObjectExpression

This was state only used by the parser to output an error with
appropriate location. This shrinks the size of ObjectExpression from
120 bytes down to just 56. This saves roughly 2.5 MiB when loading
twitter.
---
 Userland/Libraries/LibJS/AST.h      |  6 +-----
 Userland/Libraries/LibJS/Parser.cpp | 14 ++++++++++----
 Userland/Libraries/LibJS/Parser.h   |  1 +
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/Userland/Libraries/LibJS/AST.h b/Userland/Libraries/LibJS/AST.h
index 123905d6d8..e898132ba2 100644
--- a/Userland/Libraries/LibJS/AST.h
+++ b/Userland/Libraries/LibJS/AST.h
@@ -1691,10 +1691,9 @@ private:
 
 class ObjectExpression final : public Expression {
 public:
-    explicit ObjectExpression(SourceRange source_range, NonnullRefPtrVector<ObjectProperty> properties = {}, Optional<SourceRange> first_invalid_property_range = {})
+    explicit ObjectExpression(SourceRange source_range, NonnullRefPtrVector<ObjectProperty> properties = {})
         : Expression(source_range)
         , m_properties(move(properties))
-        , m_first_invalid_property_range(move(first_invalid_property_range))
     {
     }
 
@@ -1702,13 +1701,10 @@ public:
     virtual void dump(int indent) const override;
     virtual Bytecode::CodeGenerationErrorOr<void> generate_bytecode(Bytecode::Generator&) const override;
 
-    Optional<SourceRange> const& invalid_property_range() const { return m_first_invalid_property_range; }
-
 private:
     virtual bool is_object_expression() const override { return true; }
 
     NonnullRefPtrVector<ObjectProperty> m_properties;
-    Optional<SourceRange> m_first_invalid_property_range;
 };
 
 class ArrayExpression final : public Expression {
diff --git a/Userland/Libraries/LibJS/Parser.cpp b/Userland/Libraries/LibJS/Parser.cpp
index 8e41d8882f..6614094f4b 100644
--- a/Userland/Libraries/LibJS/Parser.cpp
+++ b/Userland/Libraries/LibJS/Parser.cpp
@@ -1799,10 +1799,16 @@ NonnullRefPtr<ObjectExpression> Parser::parse_object_expression()
     }
 
     consume(TokenType::CurlyClose);
+
+    if (invalid_object_literal_property_range.has_value()) {
+        size_t object_expression_offset = rule_start.position().offset;
+        VERIFY(!m_state.invalid_property_range_in_object_expression.contains(object_expression_offset));
+        m_state.invalid_property_range_in_object_expression.set(object_expression_offset, invalid_object_literal_property_range->start);
+    }
+
     return create_ast_node<ObjectExpression>(
         { m_source_code, rule_start.position(), position() },
-        move(properties),
-        move(invalid_object_literal_property_range));
+        move(properties));
 }
 
 NonnullRefPtr<ArrayExpression> Parser::parse_array_expression()
@@ -1939,8 +1945,8 @@ NonnullRefPtr<Expression> Parser::parse_expression(int min_precedence, Associati
     auto [expression, should_continue_parsing] = parse_primary_expression();
     auto check_for_invalid_object_property = [&](auto& expression) {
         if (is<ObjectExpression>(*expression)) {
-            if (auto range = static_cast<ObjectExpression&>(*expression).invalid_property_range(); range.has_value())
-                syntax_error("Invalid property in object literal", range->start);
+            if (auto start_offset = m_state.invalid_property_range_in_object_expression.get(expression->start_offset()); start_offset.has_value())
+                syntax_error("Invalid property in object literal", start_offset.value());
         }
     };
     if (is<Identifier>(*expression) && m_state.current_scope_pusher) {
diff --git a/Userland/Libraries/LibJS/Parser.h b/Userland/Libraries/LibJS/Parser.h
index 2f0e73db68..25b7513cec 100644
--- a/Userland/Libraries/LibJS/Parser.h
+++ b/Userland/Libraries/LibJS/Parser.h
@@ -282,6 +282,7 @@ private:
         ScopePusher* current_scope_pusher { nullptr };
 
         HashMap<StringView, Optional<Position>> labels_in_scope;
+        HashMap<size_t, Position> invalid_property_range_in_object_expression;
         HashTable<StringView>* referenced_private_names { nullptr };
 
         bool strict_mode { false };