From 7f717b841475449b244529eb9e7c21eef801e940 Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Wed, 1 Mar 2023 15:06:27 -0500
Subject: [PATCH] LibWeb: Store all members of WebIDL::ExceptionOr<T> in a
 single Variant

This reduces the size of WebIDL::ExceptionOr<T> as follows for a few
different Ts:

WebIDL::ExceptionOr<void>: 48 bytes to 40 bytes
WebIDL::ExceptionOr<JS::Value>: 48 bytes to 40 bytes
WebIDL::ExceptionOr<String>: 56 bytes to 40 bytes
---
 .../Libraries/LibWeb/WebIDL/ExceptionOr.h     | 32 +++++++++----------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/Userland/Libraries/LibWeb/WebIDL/ExceptionOr.h b/Userland/Libraries/LibWeb/WebIDL/ExceptionOr.h
index cb0eaa52d0c..0c40327d83b 100644
--- a/Userland/Libraries/LibWeb/WebIDL/ExceptionOr.h
+++ b/Userland/Libraries/LibWeb/WebIDL/ExceptionOr.h
@@ -37,17 +37,17 @@ class [[nodiscard]] ExceptionOr {
 public:
     ExceptionOr()
     requires(IsSame<ValueType, Empty>)
-        : m_result(Empty {})
+        : m_result_or_exception(Empty {})
     {
     }
 
     ExceptionOr(ValueType const& result)
-        : m_result(result)
+        : m_result_or_exception(result)
     {
     }
 
     ExceptionOr(ValueType&& result)
-        : m_result(move(result))
+        : m_result_or_exception(move(result))
     {
     }
 
@@ -57,31 +57,31 @@ public:
     template<typename WrappedValueType>
     ExceptionOr(WrappedValueType result)
     requires(!IsPOD<ValueType>)
-        : m_result(move(result))
+        : m_result_or_exception(ValueType { move(result) })
     {
     }
 
     ExceptionOr(JS::NonnullGCPtr<DOMException> exception)
-        : m_exception(move(exception))
+        : m_result_or_exception(exception)
     {
     }
 
     ExceptionOr(SimpleException exception)
-        : m_exception(move(exception))
+        : m_result_or_exception(move(exception))
     {
     }
 
     ExceptionOr(JS::Completion exception)
-        : m_exception(move(exception))
+        : m_result_or_exception(move(exception))
     {
-        auto const& completion = m_exception.get<JS::Completion>();
+        auto const& completion = m_result_or_exception.template get<JS::Completion>();
         VERIFY(completion.is_error());
     }
 
     ExceptionOr(Variant<SimpleException, JS::NonnullGCPtr<DOMException>, JS::Completion> exception)
-        : m_exception(move(exception).template downcast<Empty, SimpleException, JS::NonnullGCPtr<DOMException>, JS::Completion>())
+        : m_result_or_exception(move(exception))
     {
-        if (auto* completion = m_exception.template get_pointer<JS::Completion>())
+        if (auto* completion = m_result_or_exception.template get_pointer<JS::Completion>())
             VERIFY(completion->is_error());
     }
 
@@ -92,22 +92,22 @@ public:
     ValueType& value()
     requires(!IsSame<ValueType, Empty>)
     {
-        return m_result.value();
+        return m_result_or_exception.template get<ValueType>();
     }
 
     ValueType release_value()
     {
-        return m_result.release_value();
+        return move(m_result_or_exception.template get<ValueType>());
     }
 
     Variant<SimpleException, JS::NonnullGCPtr<DOMException>, JS::Completion> exception() const
     {
-        return m_exception.template downcast<SimpleException, JS::NonnullGCPtr<DOMException>, JS::Completion>();
+        return m_result_or_exception.template downcast<SimpleException, JS::NonnullGCPtr<DOMException>, JS::Completion>();
     }
 
     bool is_exception() const
     {
-        return !m_exception.template has<Empty>();
+        return !m_result_or_exception.template has<ValueType>();
     }
 
     ValueType release_value_but_fixme_should_propagate_errors()
@@ -121,10 +121,8 @@ public:
     Variant<SimpleException, JS::NonnullGCPtr<DOMException>, JS::Completion> release_error() { return exception(); }
 
 private:
-    Optional<ValueType> m_result;
-
     // https://webidl.spec.whatwg.org/#idl-exceptions
-    Variant<Empty, SimpleException, JS::NonnullGCPtr<DOMException>, JS::Completion> m_exception {};
+    Variant<ValueType, SimpleException, JS::NonnullGCPtr<DOMException>, JS::Completion> m_result_or_exception;
 };
 
 template<>