From 96600e77c2ce17eccb675eb137ec9cdd28ac0074 Mon Sep 17 00:00:00 2001
From: Andrew Kaster <akaster@serenityos.org>
Date: Mon, 21 Aug 2023 15:13:18 -0600
Subject: [PATCH] LibJS: Enable storing Value and Handle<Value> in HashMaps

We have the right conversions to make this work, so let's make it
possible to have a `HashMap<JS::Handle<T>, V>` and look for a specific
T inside it without having to create a temporary handle.

This involves adding some operator== implementations, and some
specializations of AK::Traits.
---
 Userland/Libraries/LibJS/Heap/Handle.h   | 25 ++++++++++++++++++++++++
 Userland/Libraries/LibJS/Runtime/Value.h | 17 ++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/Userland/Libraries/LibJS/Heap/Handle.h b/Userland/Libraries/LibJS/Heap/Handle.h
index d74f2426e8..f816aa9ef8 100644
--- a/Userland/Libraries/LibJS/Heap/Handle.h
+++ b/Userland/Libraries/LibJS/Heap/Handle.h
@@ -162,6 +162,9 @@ public:
     auto value() const { return *m_value; }
     bool is_null() const { return m_handle.is_null() && !m_value.has_value(); }
 
+    bool operator==(Value const& value) const { return value == m_value; }
+    bool operator==(Handle<Value> const& other) const { return other.m_value == this->m_value; }
+
 private:
     explicit Handle(Value value)
         : m_value(value)
@@ -184,3 +187,25 @@ inline Handle<Value> make_handle(Value value)
 }
 
 }
+
+namespace AK {
+
+template<typename T>
+struct Traits<JS::Handle<T>> : public GenericTraits<JS::Handle<T>> {
+    static unsigned hash(JS::Handle<T> const& handle) { return Traits<T>::hash(handle); }
+};
+
+template<>
+struct Traits<JS::Handle<JS::Value>> : public GenericTraits<JS::Handle<JS::Value>> {
+    static unsigned hash(JS::Handle<JS::Value> const& handle) { return Traits<JS::Value>::hash(handle.value()); }
+};
+
+namespace Detail {
+template<typename T>
+inline constexpr bool IsHashCompatible<JS::Handle<T>, T> = true;
+
+template<typename T>
+inline constexpr bool IsHashCompatible<T, JS::Handle<T>> = true;
+
+}
+}
diff --git a/Userland/Libraries/LibJS/Runtime/Value.h b/Userland/Libraries/LibJS/Runtime/Value.h
index 6196d1545b..85e31667cc 100644
--- a/Userland/Libraries/LibJS/Runtime/Value.h
+++ b/Userland/Libraries/LibJS/Runtime/Value.h
@@ -619,6 +619,18 @@ public:
         return *this;
     }
 
+    template<typename O>
+    ALWAYS_INLINE bool operator==(Optional<O> const& other) const
+    {
+        return has_value() == other.has_value() && (!has_value() || value() == other.value());
+    }
+
+    template<typename O>
+    ALWAYS_INLINE bool operator==(O const& other) const
+    {
+        return has_value() && value() == other;
+    }
+
     void clear()
     {
         m_value = {};
@@ -688,4 +700,9 @@ struct Formatter<JS::Value> : Formatter<StringView> {
     }
 };
 
+template<>
+struct Traits<JS::Value> : GenericTraits<JS::Value> {
+    static unsigned hash(JS::Value value) { return Traits<u64>::hash(value.encoded()); }
+};
+
 }