LibJS: Move creation of fallible VM objects to its creation factory

No change of behavior in this patch, but this will allow this factory to
propagate any errors from the creation of these objects.

Userland/Libraries/LibJS/Runtime/VM.cpp

@@ -36,7 +36,20 @@ namespace JS {
 
 NonnullRefPtr<VM> VM::create(OwnPtr<CustomData> custom_data)
 {
-    return adopt_ref(*new VM(move(custom_data)));
+    ErrorMessages error_messages {};
+    error_messages[to_underlying(ErrorMessage::OutOfMemory)] = String::from_utf8(ErrorType::OutOfMemory.message()).release_value_but_fixme_should_propagate_errors();
+
+    auto vm = adopt_ref(*new VM(move(custom_data), move(error_messages)));
+
+    WellKnownSymbols well_known_symbols {
+#define __JS_ENUMERATE(SymbolName, snake_name) \
+    Symbol::create(*vm, "Symbol." #SymbolName##_string.release_value_but_fixme_should_propagate_errors(), false),
+        JS_ENUMERATE_WELL_KNOWN_SYMBOLS
+#undef __JS_ENUMERATE
+    };
+
+    vm->set_well_known_symbols(move(well_known_symbols));
+    return vm;
 }
 
 template<u32... code_points>
@@ -47,8 +60,9 @@ static constexpr auto make_single_ascii_character_strings(IndexSequence<code_poi
 
 static constexpr auto single_ascii_character_strings = make_single_ascii_character_strings(MakeIndexSequence<128>());
 
-VM::VM(OwnPtr<CustomData> custom_data)
+VM::VM(OwnPtr<CustomData> custom_data, ErrorMessages error_messages)
     : m_heap(*this)
+    , m_error_messages(move(error_messages))
     , m_custom_data(move(custom_data))
 {
     m_empty_string = m_heap.allocate_without_realm<PrimitiveString>(String {});
@@ -150,13 +164,6 @@ VM::VM(OwnPtr<CustomData> custom_data)
         // NOTE: Since LibJS has no way of knowing whether the current environment is a browser we always
         //       call HostEnsureCanAddPrivateElement when needed.
     };
-
-#define __JS_ENUMERATE(SymbolName, snake_name) \
-    m_well_known_symbol_##snake_name = Symbol::create(*this, "Symbol." #SymbolName##_string.release_value_but_fixme_should_propagate_errors(), false);
-    JS_ENUMERATE_WELL_KNOWN_SYMBOLS
-#undef __JS_ENUMERATE
-
-    m_error_messages[to_underlying(ErrorMessage::OutOfMemory)] = String::from_utf8(ErrorType::OutOfMemory.message()).release_value_but_fixme_should_propagate_errors();
 }
 
 String const& VM::error_message(ErrorMessage type) const

Userland/Libraries/LibJS/Runtime/VM.h

@@ -68,7 +68,7 @@ public:
 #define __JS_ENUMERATE(SymbolName, snake_name)     \
     Symbol* well_known_symbol_##snake_name() const \
     {                                              \
-        return m_well_known_symbol_##snake_name;   \
+        return m_well_known_symbols.snake_name;    \
     }
     JS_ENUMERATE_WELL_KNOWN_SYMBOLS
 #undef __JS_ENUMERATE
@@ -269,7 +269,16 @@ public:
     Function<ThrowCompletionOr<void>(Object&)> host_ensure_can_add_private_element;
 
 private:
-    explicit VM(OwnPtr<CustomData>);
+    using ErrorMessages = AK::Array<String, to_underlying(ErrorMessage::__Count)>;
+
+    struct WellKnownSymbols {
+#define __JS_ENUMERATE(SymbolName, snake_name) \
+    GCPtr<Symbol> snake_name;
+        JS_ENUMERATE_WELL_KNOWN_SYMBOLS
+#undef __JS_ENUMERATE
+    };
+
+    VM(OwnPtr<CustomData>, ErrorMessages);
 
     ThrowCompletionOr<void> property_binding_initialization(BindingPattern const& binding, Value value, Environment* environment);
     ThrowCompletionOr<void> iterator_binding_initialization(BindingPattern const& binding, Iterator& iterator_record, Environment* environment);
@@ -280,6 +289,8 @@ private:
     ThrowCompletionOr<void> import_module_dynamically(ScriptOrModule referencing_script_or_module, ModuleRequest module_request, PromiseCapability const& promise_capability);
     void finish_dynamic_import(ScriptOrModule referencing_script_or_module, ModuleRequest module_request, PromiseCapability const& promise_capability, Promise* inner_promise);
 
+    void set_well_known_symbols(WellKnownSymbols well_known_symbols) { m_well_known_symbols = move(well_known_symbols); }
+
     HashMap<String, GCPtr<PrimitiveString>> m_string_cache;
     HashMap<DeprecatedString, GCPtr<PrimitiveString>> m_deprecated_string_cache;
 
@@ -301,7 +312,7 @@ private:
 
     GCPtr<PrimitiveString> m_empty_string;
     GCPtr<PrimitiveString> m_single_ascii_character_strings[128] {};
-    AK::Array<String, to_underlying(ErrorMessage::__Count)> m_error_messages;
+    ErrorMessages m_error_messages;
 
     struct StoredModule {
         ScriptOrModule referencing_script_or_module;
@@ -315,10 +326,7 @@ private:
 
     Vector<StoredModule> m_loaded_modules;
 
-#define __JS_ENUMERATE(SymbolName, snake_name) \
-    GCPtr<Symbol> m_well_known_symbol_##snake_name;
-    JS_ENUMERATE_WELL_KNOWN_SYMBOLS
-#undef __JS_ENUMERATE
+    WellKnownSymbols m_well_known_symbols;
 
     u32 m_execution_generation { 0 };