LibJS: Convert to_string() to ThrowCompletionOr

Also update get_function_name() to use ThrowCompletionOr, but this is
not a standard AO and should be refactored out of existence eventually.

Meta/Lagom/Fuzzers/FuzzilliJs.cpp

@@ -141,10 +141,7 @@ JS_DEFINE_NATIVE_FUNCTION(TestRunnerGlobalObject::fuzzilli)
     if (!vm.argument_count())
         return JS::js_undefined();
 
-    auto operation = vm.argument(0).to_string(global_object);
+    auto operation = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
-
     if (operation == "FUZZILLI_CRASH") {
         auto type = vm.argument(1).to_i32(global_object);
         if (vm.exception())
@@ -164,9 +161,7 @@ JS_DEFINE_NATIVE_FUNCTION(TestRunnerGlobalObject::fuzzilli)
             fzliout = stdout;
         }
 
-        auto string = vm.argument(1).to_string(global_object);
+        auto string = TRY_OR_DISCARD(vm.argument(1).to_string(global_object));
-        if (vm.exception())
-            return {};
         fprintf(fzliout, "%s\n", string.characters());
         fflush(fzliout);
     }

Meta/Lagom/Tools/CodeGenerators/LibWeb/WrapperGenerator.cpp

@@ -906,19 +906,24 @@ static void generate_to_cpp(SourceGenerator& generator, ParameterType& parameter
         if (!optional) {
             if (!parameter.type.nullable) {
                 scoped_generator.append(R"~~~(
-    auto @cpp_name@ = @js_name@@js_suffix@.is_null() && @legacy_null_to_empty_string@
+    String @cpp_name@;
-        ? String::empty()
+    if (@js_name@@js_suffix@.is_null() && @legacy_null_to_empty_string@) {
-        : @js_name@@js_suffix@.to_string(global_object);
+        @cpp_name@ = String::empty();
-    if (vm.exception())
+    } else {
-        @return_statement@
+        auto to_string_result = @js_name@@js_suffix@.to_string(global_object);
+        if (to_string_result.is_error())
+            @return_statement@
+        @cpp_name@ = to_string_result.release_value();
+    }
 )~~~");
             } else {
                 scoped_generator.append(R"~~~(
     String @cpp_name@;
     if (!@js_name@@js_suffix@.is_nullish()) {
-        @cpp_name@ = @js_name@@js_suffix@.to_string(global_object);
+        auto to_string_result = @js_name@@js_suffix@.to_string(global_object);
-        if (vm.exception())
+        if (to_string_result.is_error())
             @return_statement@
+        @cpp_name@ = to_string_result.release_value();
     }
 )~~~");
             }
@@ -926,11 +931,14 @@ static void generate_to_cpp(SourceGenerator& generator, ParameterType& parameter
             scoped_generator.append(R"~~~(
     String @cpp_name@;
     if (!@js_name@@js_suffix@.is_undefined()) {
-        @cpp_name@ = @js_name@@js_suffix@.is_null() && @legacy_null_to_empty_string@
+        if (@js_name@@js_suffix@.is_null() && @legacy_null_to_empty_string@) {
-            ? String::empty()
+            @cpp_name@ = String::empty();
-            : @js_name@@js_suffix@.to_string(global_object);
+        } else {
-        if (vm.exception())
+            auto to_string_result = @js_name@@js_suffix@.to_string(global_object);
-            @return_statement@
+            if (to_string_result.is_error())
+                @return_statement@
+            @cpp_name@ = to_string_result.release_value();
+        }
     })~~~");
             if (optional_default_value.has_value() && (!parameter.type.nullable || optional_default_value.value() != "null")) {
                 scoped_generator.append(R"~~~( else {

Tests/LibJS/test-js.cpp

@@ -18,9 +18,7 @@ TESTJS_GLOBAL_FUNCTION(is_strict_mode, isStrictMode, 0)
 
 TESTJS_GLOBAL_FUNCTION(can_parse_source, canParseSource)
 {
-    auto source = vm.argument(0).to_string(global_object);
+    auto source = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto parser = JS::Parser(JS::Lexer(source));
     parser.parse_program();
     return JS::Value(!parser.has_errors());

Tests/LibWasm/test-wasm.cpp

@@ -13,9 +13,7 @@ TEST_ROOT("Userland/Libraries/LibWasm/Tests");
 
 TESTJS_GLOBAL_FUNCTION(read_binary_wasm_file, readBinaryWasmFile)
 {
-    auto filename = vm.argument(0).to_string(global_object);
+    auto filename = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto file = Core::File::open(filename, Core::OpenMode::ReadOnly);
     if (file.is_error()) {
         vm.throw_exception<JS::TypeError>(global_object, file.error().string());
@@ -169,9 +167,7 @@ void WebAssemblyModule::initialize(JS::GlobalObject& global_object)
 
 JS_DEFINE_NATIVE_FUNCTION(WebAssemblyModule::get_export)
 {
-    auto name = vm.argument(0).to_string(global_object);
+    auto name = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto this_value = vm.this_value(global_object);
     auto object = this_value.to_object(global_object);
     if (vm.exception())

Tests/LibWeb/test-web.cpp

@@ -40,9 +40,7 @@ TESTJS_MAIN_HOOK()
 
 TESTJS_GLOBAL_FUNCTION(load_local_page, loadLocalPage)
 {
-    auto name = vm.argument(0).to_string(global_object);
+    auto name = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
 
     // Clear the hooks
     before_initial_load_hooks.clear();

Userland/Applications/Spreadsheet/SpreadsheetModel.cpp

@@ -40,7 +40,7 @@ GUI::Variant SheetModel::data(const GUI::ModelIndex& index, GUI::ModelRole role)
                         return builder.to_string();
                     }
                 }
-                auto error = value.to_string(cell->sheet().global_object());
+                auto error = value.to_string_without_side_effects();
                 // This is annoying, but whatever.
                 cell->sheet().interpreter().vm().clear_exception();
 

Userland/Libraries/LibJS/AST.cpp

@@ -73,7 +73,7 @@ static void update_function_name(Value value, FlyString const& name)
         static_cast<ECMAScriptFunctionObject&>(function).set_name(name);
 }
 
-static String get_function_name(GlobalObject& global_object, Value value)
+static ThrowCompletionOr<String> get_function_name(GlobalObject& global_object, Value value)
 {
     if (value.is_symbol())
         return String::formatted("[{}]", value.as_symbol().description());
@@ -1285,11 +1285,11 @@ ThrowCompletionOr<Value> ClassExpression::class_definition_evaluation(Interprete
             TRY(target.define_property_or_throw(property_key, { .value = method_value, .writable = true, .enumerable = false, .configurable = true }));
             break;
         case ClassMethod::Kind::Getter:
-            update_function_name(method_value, String::formatted("get {}", get_function_name(global_object, key)));
+            update_function_name(method_value, String::formatted("get {}", TRY(get_function_name(global_object, key))));
             TRY(target.define_property_or_throw(property_key, { .get = &method_function, .enumerable = true, .configurable = true }));
             break;
         case ClassMethod::Kind::Setter:
-            update_function_name(method_value, String::formatted("set {}", get_function_name(global_object, key)));
+            update_function_name(method_value, String::formatted("set {}", TRY(get_function_name(global_object, key))));
             TRY(target.define_property_or_throw(property_key, { .set = &method_function, .enumerable = true, .configurable = true }));
             break;
         default:
@@ -2346,7 +2346,7 @@ Value ObjectExpression::execute(Interpreter& interpreter, GlobalObject& global_o
         if (value.is_function() && property.is_method())
             static_cast<ECMAScriptFunctionObject&>(value.as_function()).set_home_object(object);
 
-        String name = get_function_name(global_object, key);
+        auto name = TRY_OR_DISCARD(get_function_name(global_object, key));
         if (property.type() == ObjectProperty::Type::Getter) {
             name = String::formatted("get {}", name);
         } else if (property.type() == ObjectProperty::Type::Setter) {
@@ -2640,9 +2640,7 @@ Value TemplateLiteral::execute(Interpreter& interpreter, GlobalObject& global_ob
         auto expr = expression.execute(interpreter, global_object);
         if (interpreter.exception())
             return {};
-        auto string = expr.to_string(global_object);
+        auto string = TRY_OR_DISCARD(expr.to_string(global_object));
-        if (interpreter.exception())
-            return {};
         string_builder.append(string);
     }
 

Userland/Libraries/LibJS/Runtime/AbstractOperations.cpp

@@ -929,10 +929,7 @@ ThrowCompletionOr<String> get_substitution(GlobalObject& global_object, Utf16Vie
                 auto& value = captures[*capture_position - 1];
 
                 if (!value.is_undefined()) {
-                    auto value_string = value.to_string(global_object);
+                    auto value_string = TRY(value.to_string(global_object));
-                    if (auto* exception = vm.exception())
-                        return throw_completion(exception->value());
-
                     result.append(value_string);
                 }
 
@@ -960,10 +957,7 @@ ThrowCompletionOr<String> get_substitution(GlobalObject& global_object, Utf16Vie
                 auto capture = TRY(named_captures.as_object().get(group_name));
 
                 if (!capture.is_undefined()) {
-                    auto capture_string = capture.to_string(global_object);
+                    auto capture_string = TRY(capture.to_string(global_object));
-                    if (auto* exception = vm.exception())
-                        return throw_completion(exception->value());
-
                     result.append(capture_string);
                 }
 

Userland/Libraries/LibJS/Runtime/AggregateErrorConstructor.cpp

@@ -45,9 +45,7 @@ Value AggregateErrorConstructor::construct(FunctionObject& new_target)
     auto* aggregate_error = TRY_OR_DISCARD(ordinary_create_from_constructor<AggregateError>(global_object, new_target, &GlobalObject::aggregate_error_prototype));
 
     if (!vm.argument(1).is_undefined()) {
-        auto message = vm.argument(1).to_string(global_object);
+        auto message = TRY_OR_DISCARD(vm.argument(1).to_string(global_object));
-        if (vm.exception())
-            return {};
         MUST(aggregate_error->create_non_enumerable_data_property_or_throw(vm.names.message, js_string(vm, message)));
     }
 

Userland/Libraries/LibJS/Runtime/ArrayPrototype.cpp

@@ -457,9 +457,7 @@ JS_DEFINE_NATIVE_FUNCTION(ArrayPrototype::to_locale_string)
         if (value.is_nullish())
             continue;
         auto locale_string_result = TRY_OR_DISCARD(value.invoke(global_object, vm.names.toLocaleString));
-        auto string = locale_string_result.to_string(global_object);
+        auto string = TRY_OR_DISCARD(locale_string_result.to_string(global_object));
-        if (vm.exception())
-            return {};
         builder.append(string);
     }
     return js_string(vm, builder.to_string());
@@ -484,11 +482,8 @@ JS_DEFINE_NATIVE_FUNCTION(ArrayPrototype::join)
 
     auto length = TRY_OR_DISCARD(length_of_array_like(global_object, *this_object));
     String separator = ",";
-    if (!vm.argument(0).is_undefined()) {
+    if (!vm.argument(0).is_undefined())
-        separator = vm.argument(0).to_string(global_object);
+        separator = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
-            return {};
-    }
     StringBuilder builder;
     for (size_t i = 0; i < length; ++i) {
         if (i > 0)
@@ -496,9 +491,7 @@ JS_DEFINE_NATIVE_FUNCTION(ArrayPrototype::join)
         auto value = TRY_OR_DISCARD(this_object->get(i));
         if (value.is_nullish())
             continue;
-        auto string = value.to_string(global_object);
+        auto string = TRY_OR_DISCARD(value.to_string(global_object));
-        if (vm.exception())
-            return {};
         builder.append(string);
     }
 

Userland/Libraries/LibJS/Runtime/DateConstructor.cpp

@@ -319,9 +319,7 @@ JS_DEFINE_NATIVE_FUNCTION(DateConstructor::parse)
     if (!vm.argument_count())
         return js_nan();
 
-    auto date_string = vm.argument(0).to_string(global_object);
+    auto date_string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
 
     return parse_date_string(date_string);
 }

Userland/Libraries/LibJS/Runtime/ErrorConstructor.cpp

@@ -42,9 +42,7 @@ Value ErrorConstructor::construct(FunctionObject& new_target)
     auto* error = TRY_OR_DISCARD(ordinary_create_from_constructor<Error>(global_object, new_target, &GlobalObject::error_prototype));
 
     if (!vm.argument(0).is_undefined()) {
-        auto message = vm.argument(0).to_string(global_object);
+        auto message = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
-            return {};
         MUST(error->create_non_enumerable_data_property_or_throw(vm.names.message, js_string(vm, message)));
     }
 
@@ -89,9 +87,7 @@ Value ErrorConstructor::construct(FunctionObject& new_target)
             global_object, new_target, &GlobalObject::snake_name##_prototype));                                  \
                                                                                                                  \
         if (!vm.argument(0).is_undefined()) {                                                                    \
-            auto message = vm.argument(0).to_string(global_object);                                              \
+            auto message = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));                              \
-            if (vm.exception())                                                                                  \
-                return {};                                                                                       \
             MUST(error->create_non_enumerable_data_property_or_throw(vm.names.message, js_string(vm, message))); \
         }                                                                                                        \
                                                                                                                  \

Userland/Libraries/LibJS/Runtime/ErrorPrototype.cpp

@@ -41,19 +41,13 @@ JS_DEFINE_NATIVE_FUNCTION(ErrorPrototype::to_string)
 
     String name = "Error";
     auto name_property = TRY_OR_DISCARD(this_object.get(vm.names.name));
-    if (!name_property.is_undefined()) {
+    if (!name_property.is_undefined())
-        name = name_property.to_string(global_object);
+        name = TRY_OR_DISCARD(name_property.to_string(global_object));
-        if (vm.exception())
-            return {};
-    }
 
     String message = "";
     auto message_property = TRY_OR_DISCARD(this_object.get(vm.names.message));
-    if (!message_property.is_undefined()) {
+    if (!message_property.is_undefined())
-        message = message_property.to_string(global_object);
+        message = TRY_OR_DISCARD(message_property.to_string(global_object));
-        if (vm.exception())
-            return {};
-    }
 
     if (name.is_empty())
         return js_string(vm, message);

Userland/Libraries/LibJS/Runtime/FunctionConstructor.cpp

@@ -41,24 +41,16 @@ RefPtr<FunctionExpression> FunctionConstructor::create_dynamic_function_node(Glo
     auto& vm = global_object.vm();
     String parameters_source = "";
     String body_source = "";
-    if (vm.argument_count() == 1) {
+    if (vm.argument_count() == 1)
-        body_source = vm.argument(0).to_string(global_object);
+        body_source = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
-            return {};
-    }
     if (vm.argument_count() > 1) {
         Vector<String> parameters;
-        for (size_t i = 0; i < vm.argument_count() - 1; ++i) {
+        for (size_t i = 0; i < vm.argument_count() - 1; ++i)
-            parameters.append(vm.argument(i).to_string(global_object));
+            parameters.append(TRY_OR_DISCARD(vm.argument(i).to_string(global_object)));
-            if (vm.exception())
-                return {};
-        }
         StringBuilder parameters_builder;
         parameters_builder.join(',', parameters);
         parameters_source = parameters_builder.build();
-        body_source = vm.argument(vm.argument_count() - 1).to_string(global_object);
+        body_source = TRY_OR_DISCARD(vm.argument(vm.argument_count() - 1).to_string(global_object));
-        if (vm.exception())
-            return {};
     }
     auto is_generator = kind == FunctionKind::Generator;
     auto source = String::formatted("function{} anonymous({}\n) {{\n{}\n}}", is_generator ? "*" : "", parameters_source, body_source);

Userland/Libraries/LibJS/Runtime/GlobalObject.cpp

@@ -347,9 +347,7 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_float)
 {
     if (vm.argument(0).is_number())
         return vm.argument(0);
-    auto input_string = vm.argument(0).to_string(global_object);
+    auto input_string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto trimmed_string = input_string.trim_whitespace(TrimMode::Left);
     for (size_t length = trimmed_string.length(); length > 0; --length) {
         // This can't throw, so no exception check is fine.
@@ -363,9 +361,7 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_float)
 // 19.2.5 parseInt ( string, radix ), https://tc39.es/ecma262/#sec-parseint-string-radix
 JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_int)
 {
-    auto input_string = vm.argument(0).to_string(global_object);
+    auto input_string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
 
     // FIXME: There's a bunch of unnecessary string copying here.
     double sign = 1;
@@ -500,9 +496,7 @@ static String decode(JS::GlobalObject& global_object, const String& string, Stri
 // 19.2.6.4 encodeURI ( uri ), https://tc39.es/ecma262/#sec-encodeuri-uri
 JS_DEFINE_NATIVE_FUNCTION(GlobalObject::encode_uri)
 {
-    auto uri_string = vm.argument(0).to_string(global_object);
+    auto uri_string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto encoded = encode(global_object, uri_string, ";/?:@&=+$,abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.!~*'()#"sv);
     if (vm.exception())
         return {};
@@ -512,9 +506,7 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::encode_uri)
 // 19.2.6.2 decodeURI ( encodedURI ), https://tc39.es/ecma262/#sec-decodeuri-encodeduri
 JS_DEFINE_NATIVE_FUNCTION(GlobalObject::decode_uri)
 {
-    auto uri_string = vm.argument(0).to_string(global_object);
+    auto uri_string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto decoded = decode(global_object, uri_string, ";/?:@&=+$,#"sv);
     if (vm.exception())
         return {};
@@ -524,9 +516,7 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::decode_uri)
 // 19.2.6.5 encodeURIComponent ( uriComponent ), https://tc39.es/ecma262/#sec-encodeuricomponent-uricomponent
 JS_DEFINE_NATIVE_FUNCTION(GlobalObject::encode_uri_component)
 {
-    auto uri_string = vm.argument(0).to_string(global_object);
+    auto uri_string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto encoded = encode(global_object, uri_string, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.!~*'()"sv);
     if (vm.exception())
         return {};
@@ -536,9 +526,7 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::encode_uri_component)
 // 19.2.6.3 decodeURIComponent ( encodedURIComponent ), https://tc39.es/ecma262/#sec-decodeuricomponent-encodeduricomponent
 JS_DEFINE_NATIVE_FUNCTION(GlobalObject::decode_uri_component)
 {
-    auto uri_string = vm.argument(0).to_string(global_object);
+    auto uri_string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto decoded = decode(global_object, uri_string, ""sv);
     if (vm.exception())
         return {};
@@ -548,9 +536,7 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::decode_uri_component)
 // B.2.1.1 escape ( string ), https://tc39.es/ecma262/#sec-escape-string
 JS_DEFINE_NATIVE_FUNCTION(GlobalObject::escape)
 {
-    auto string = vm.argument(0).to_string(global_object);
+    auto string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     StringBuilder escaped;
     for (auto code_point : Utf8View(string)) {
         if (code_point < 256) {
@@ -568,9 +554,7 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::escape)
 // B.2.1.2 unescape ( string ), https://tc39.es/ecma262/#sec-unescape-string
 JS_DEFINE_NATIVE_FUNCTION(GlobalObject::unescape)
 {
-    auto string = vm.argument(0).to_string(global_object);
+    auto string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     ssize_t length = string.length();
     StringBuilder unescaped(length);
     for (auto k = 0; k < length; ++k) {

Userland/Libraries/LibJS/Runtime/Intl/AbstractOperations.cpp

@@ -246,9 +246,7 @@ ThrowCompletionOr<Vector<String>> canonicalize_locale_list(GlobalObject& global_
             // iv. Else,
             else {
                 // 1. Let tag be ? ToString(kValue).
-                tag = key_value.to_string(global_object);
+                tag = TRY(key_value.to_string(global_object));
-                if (auto* exception = vm.exception())
-                    return throw_completion(exception->value());
             }
 
             // v. If IsStructurallyValidLanguageTag(tag) is false, throw a RangeError exception.

Userland/Libraries/LibJS/Runtime/Intl/DisplayNamesPrototype.cpp

@@ -44,9 +44,7 @@ JS_DEFINE_NATIVE_FUNCTION(DisplayNamesPrototype::of)
         return {};
 
     // 3. Let code be ? ToString(code).
-    auto code_string = code.to_string(global_object);
+    auto code_string = TRY_OR_DISCARD(code.to_string(global_object));
-    if (vm.exception())
-        return {};
     code = js_string(vm, move(code_string));
 
     // 4. Let code be ? CanonicalCodeForDisplayNames(displayNames.[[Type]], code).

Userland/Libraries/LibJS/Runtime/Intl/LocaleConstructor.cpp

@@ -292,9 +292,7 @@ Value LocaleConstructor::construct(FunctionObject& new_target)
     // 9. Else,
     else {
         // a. Let tag be ? ToString(tag).
-        tag = tag_value.to_string(global_object);
+        tag = TRY_OR_DISCARD(tag_value.to_string(global_object));
-        if (vm.exception())
-            return {};
     }
 
     // 10. Set options to ? CoerceOptionsToObject(options).
@@ -343,7 +341,7 @@ Value LocaleConstructor::construct(FunctionObject& new_target)
     // 24. If kn is not undefined, set kn to ! ToString(kn).
     // 25. Set opt.[[kn]] to kn.
     if (!kn.is_undefined())
-        opt.kn = kn.to_string(global_object);
+        opt.kn = TRY_OR_DISCARD(kn.to_string(global_object));
 
     // 26. Let numberingSystem be ? GetOption(options, "numberingSystem", "string", undefined, undefined).
     // 27. If numberingSystem is not undefined, then

Userland/Libraries/LibJS/Runtime/JSONObject.cpp

@@ -65,14 +65,11 @@ String JSONObject::stringify_impl(GlobalObject& global_object, Value value, Valu
                     if (replacer_value.is_string()) {
                         item = replacer_value.as_string().string();
                     } else if (replacer_value.is_number()) {
-                        item = replacer_value.to_string(global_object);
+                        item = MUST(replacer_value.to_string(global_object));
                     } else if (replacer_value.is_object()) {
                         auto& value_object = replacer_value.as_object();
-                        if (is<StringObject>(value_object) || is<NumberObject>(value_object)) {
+                        if (is<StringObject>(value_object) || is<NumberObject>(value_object))
-                            item = replacer_value.to_string(global_object);
+                            item = TRY_OR_DISCARD(replacer_value.to_string(global_object));
-                            if (vm.exception())
-                                return {};
-                        }
                     }
                     if (!item.is_null() && !list.contains_slow(item)) {
                         list.append(item);
@@ -178,7 +175,7 @@ String JSONObject::serialize_json_property(GlobalObject& global_object, Stringif
         return quote_json_string(value.as_string().string());
     if (value.is_number()) {
         if (value.is_finite_number())
-            return value.to_string(global_object);
+            return MUST(value.to_string(global_object));
         return "null";
     }
     if (value.is_bigint()) {
@@ -392,9 +389,7 @@ String JSONObject::quote_json_string(String string)
 // 25.5.1 JSON.parse ( text [ , reviver ] ), https://tc39.es/ecma262/#sec-json.parse
 JS_DEFINE_NATIVE_FUNCTION(JSONObject::parse)
 {
-    auto string = vm.argument(0).to_string(global_object);
+    auto string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto reviver = vm.argument(1);
 
     auto json = JsonValue::from_string(string);

Userland/Libraries/LibJS/Runtime/NumberPrototype.cpp

@@ -78,11 +78,11 @@ JS_DEFINE_NATIVE_FUNCTION(NumberPrototype::to_fixed)
     }
 
     if (!number_value.is_finite_number())
-        return js_string(vm, number_value.to_string(global_object));
+        return js_string(vm, TRY_OR_DISCARD(number_value.to_string(global_object)));
 
     auto number = number_value.as_double();
     if (fabs(number) >= 1e+21)
-        return js_string(vm, number_value.to_string(global_object));
+        return js_string(vm, MUST(number_value.to_string(global_object)));
 
     return js_string(vm, String::formatted("{:0.{1}}", number, static_cast<size_t>(fraction_digits)));
 }

Userland/Libraries/LibJS/Runtime/PropertyName.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/FlyString.h>
+#include <LibJS/Runtime/Completion.h>
 #include <LibJS/Runtime/StringOrSymbol.h>
 
 namespace JS {
@@ -33,10 +34,7 @@ public:
             return value.as_symbol();
         if (value.is_integral_number() && value.as_double() >= 0 && value.as_double() < NumericLimits<u32>::max())
             return value.as_u32();
-        auto string = value.to_string(global_object);
+        return TRY_OR_DISCARD(value.to_string(global_object));
-        if (string.is_null())
-            return {};
-        return string;
     }
 
     PropertyName() { }

Userland/Libraries/LibJS/Runtime/RegExpObject.cpp

@@ -148,9 +148,7 @@ RegExpObject* RegExpObject::regexp_initialize(GlobalObject& global_object, Value
     if (flags.is_undefined()) {
         f = String::empty();
     } else {
-        f = flags.to_string(global_object);
+        f = TRY_OR_DISCARD(flags.to_string(global_object));
-        if (vm.exception())
-            return {};
     }
 
     String original_pattern;
@@ -160,10 +158,7 @@ RegExpObject* RegExpObject::regexp_initialize(GlobalObject& global_object, Value
         original_pattern = String::empty();
         parsed_pattern = String::empty();
     } else {
-        original_pattern = pattern.to_string(global_object);
+        original_pattern = TRY_OR_DISCARD(pattern.to_string(global_object));
-        if (vm.exception())
-            return {};
-
         bool unicode = f.find('u').has_value();
         parsed_pattern = parse_regex_pattern(original_pattern, unicode);
     }

Userland/Libraries/LibJS/Runtime/RegExpPrototype.cpp

@@ -377,14 +377,10 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::to_string)
         return {};
 
     auto source_attr = TRY_OR_DISCARD(regexp_object->get(vm.names.source));
-    auto pattern = source_attr.to_string(global_object);
+    auto pattern = TRY_OR_DISCARD(source_attr.to_string(global_object));
-    if (vm.exception())
-        return {};
 
     auto flags_attr = TRY_OR_DISCARD(regexp_object->get(vm.names.flags));
-    auto flags = flags_attr.to_string(global_object);
+    auto flags = TRY_OR_DISCARD(flags_attr.to_string(global_object));
-    if (vm.exception())
-        return {};
 
     return js_string(vm, String::formatted("/{}/{}", pattern, flags));
 }
@@ -434,9 +430,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_match)
         if (!result_object)
             return {};
         auto match_object = TRY_OR_DISCARD(result_object->get(0));
-        auto match_str = match_object.to_string(global_object);
+        auto match_str = TRY_OR_DISCARD(match_object.to_string(global_object));
-        if (vm.exception())
-            return {};
 
         TRY_OR_DISCARD(array->create_data_property_or_throw(n, js_string(vm, match_str)));
 
@@ -460,9 +454,8 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_match_all)
 
     auto* constructor = TRY_OR_DISCARD(species_constructor(global_object, *regexp_object, *global_object.regexp_constructor()));
 
-    auto flags = TRY_OR_DISCARD(regexp_object->get(vm.names.flags)).to_string(global_object);
+    auto flags_value = TRY_OR_DISCARD(regexp_object->get(vm.names.flags));
-    if (vm.exception())
+    auto flags = TRY_OR_DISCARD(flags_value.to_string(global_object));
-        return {};
 
     bool global = flags.find('g').has_value();
     bool unicode = flags.find('u').has_value();
@@ -501,13 +494,8 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_replace)
     auto string_view = string.view();
 
     if (!replace_value.is_function()) {
-        auto replace_string = replace_value.to_string(global_object);
+        auto replace_string = TRY_OR_DISCARD(replace_value.to_string(global_object));
-        if (vm.exception())
-            return {};
-
         replace_value = js_string(vm, move(replace_string));
-        if (vm.exception())
-            return {};
     }
 
     bool global = TRY_OR_DISCARD(regexp_object->get(vm.names.global)).to_boolean();
@@ -537,9 +525,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_replace)
             break;
 
         auto match_object = TRY_OR_DISCARD(result_object->get(0));
-        String match_str = match_object.to_string(global_object);
+        auto match_str = TRY_OR_DISCARD(match_object.to_string(global_object));
-        if (vm.exception())
-            return {};
 
         if (match_str.is_empty())
             TRY_OR_DISCARD(increment_last_index(global_object, *regexp_object, string_view, unicode));
@@ -569,15 +555,8 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_replace)
         MarkedValueList captures(vm.heap());
         for (size_t n = 1; n <= n_captures; ++n) {
             auto capture = TRY_OR_DISCARD(result.get(n));
-            if (!capture.is_undefined()) {
+            if (!capture.is_undefined())
-                auto capture_string = capture.to_string(global_object);
+                capture = js_string(vm, TRY_OR_DISCARD(capture.to_string(global_object)));
-                if (vm.exception())
-                    return {};
-
-                capture = Value(js_string(vm, capture_string));
-                if (vm.exception())
-                    return {};
-            }
 
             captures.append(move(capture));
         }
@@ -597,10 +576,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_replace)
             }
 
             auto replace_result = TRY_OR_DISCARD(vm.call(replace_value.as_function(), js_undefined(), move(replacer_args)));
-
+            replacement = TRY_OR_DISCARD(replace_result.to_string(global_object));
-            replacement = replace_result.to_string(global_object);
-            if (vm.exception())
-                return {};
         } else {
             auto named_captures_object = js_undefined();
             if (!named_captures.is_undefined()) {
@@ -677,9 +653,8 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_split)
 
     auto* constructor = TRY_OR_DISCARD(species_constructor(global_object, *regexp_object, *global_object.regexp_constructor()));
 
-    auto flags = TRY_OR_DISCARD(regexp_object->get(vm.names.flags)).to_string(global_object);
+    auto flags_value = TRY_OR_DISCARD(regexp_object->get(vm.names.flags));
-    if (vm.exception())
+    auto flags = TRY_OR_DISCARD(flags_value.to_string(global_object));
-        return {};
 
     bool unicode = flags.find('u').has_value();
     auto new_flags = flags.find('y').has_value() ? move(flags) : String::formatted("{}y", flags);

Userland/Libraries/LibJS/Runtime/RegExpStringIteratorPrototype.cpp

@@ -58,10 +58,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpStringIteratorPrototype::next)
     if (!match_object)
         return {};
     auto match_string_value = TRY_OR_DISCARD(match_object->get(0));
-    auto match_string = match_string_value.to_string(global_object);
+    auto match_string = TRY_OR_DISCARD(match_string_value.to_string(global_object));
-    if (vm.exception())
-        return {};
-
     if (match_string.is_empty()) {
         auto last_index = TRY_OR_DISCARD(iterator->regexp_object().get(vm.names.lastIndex)).to_length(global_object);
         if (vm.exception())

Userland/Libraries/LibJS/Runtime/StringConstructor.cpp

@@ -94,9 +94,8 @@ JS_DEFINE_NATIVE_FUNCTION(StringConstructor::raw)
     StringBuilder builder;
     for (size_t i = 0; i < literal_segments; ++i) {
         auto next_key = String::number(i);
-        auto next_segment = TRY_OR_DISCARD(raw->get(next_key)).to_string(global_object);
+        auto next_segment_value = TRY_OR_DISCARD(raw->get(next_key));
-        if (vm.exception())
+        auto next_segment = TRY_OR_DISCARD(next_segment_value.to_string(global_object));
-            return {};
 
         builder.append(next_segment);
 
@@ -105,9 +104,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringConstructor::raw)
 
         if (i < number_of_substituions) {
             auto next = vm.argument(i + 1);
-            auto next_sub = next.to_string(global_object);
+            auto next_sub = TRY_OR_DISCARD(next.to_string(global_object));
-            if (vm.exception())
-                return {};
             builder.append(next_sub);
         }
     }

Userland/Libraries/LibJS/Runtime/StringPrototype.cpp

@@ -31,7 +31,7 @@ namespace JS {
 static Optional<String> ak_string_from(VM& vm, GlobalObject& global_object)
 {
     auto this_value = TRY_OR_DISCARD(require_object_coercible(global_object, vm.this_value(global_object)));
-    return this_value.to_string(global_object);
+    return TRY_OR_DISCARD(this_value.to_string(global_object));
 }
 
 static Utf16String utf16_string_from(VM& vm, GlobalObject& global_object)
@@ -564,9 +564,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::concat)
     StringBuilder builder;
     builder.append(*string);
     for (size_t i = 0; i < vm.argument_count(); ++i) {
-        auto string_argument = vm.argument(i).to_string(global_object);
+        auto string_argument = TRY_OR_DISCARD(vm.argument(i).to_string(global_object));
-        if (vm.exception())
-            return {};
         builder.append(string_argument);
     }
     return js_string(vm, builder.to_string());
@@ -846,9 +844,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::at)
 JS_DEFINE_NATIVE_FUNCTION(StringPrototype::symbol_iterator)
 {
     auto this_object = TRY_OR_DISCARD(require_object_coercible(global_object, vm.this_value(global_object)));
-    auto string = this_object.to_string(global_object);
+    auto string = TRY_OR_DISCARD(this_object.to_string(global_object));
-    if (vm.exception())
-        return {};
     return StringIterator::create(global_object, string);
 }
 
@@ -882,9 +878,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::match_all)
         if (is_regexp) {
             auto flags = TRY_OR_DISCARD(regexp.as_object().get("flags"));
             auto flags_object = TRY_OR_DISCARD(require_object_coercible(global_object, flags));
-            auto flags_string = flags_object.to_string(global_object);
+            auto flags_string = TRY_OR_DISCARD(flags_object.to_string(global_object));
-            if (vm.exception())
-                return {};
             if (!flags_string.contains("g")) {
                 vm.throw_exception<TypeError>(global_object, ErrorType::StringNonGlobalRegExp);
                 return {};
@@ -941,10 +935,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::replace)
 
     if (replace_value.is_function()) {
         auto result = TRY_OR_DISCARD(vm.call(replace_value.as_function(), js_undefined(), js_string(vm, search_string), Value(position.value()), js_string(vm, string)));
-
+        replacement = TRY_OR_DISCARD(result.to_string(global_object));
-        replacement = result.to_string(global_object);
-        if (vm.exception())
-            return {};
     } else {
         replacement = TRY_OR_DISCARD(get_substitution(global_object, search_string.view(), string.view(), *position, {}, js_undefined(), replace_value));
     }
@@ -970,9 +961,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::replace_all)
         if (is_regexp) {
             auto flags = TRY_OR_DISCARD(search_value.as_object().get(vm.names.flags));
             auto flags_object = TRY_OR_DISCARD(require_object_coercible(global_object, flags));
-            auto flags_string = flags_object.to_string(global_object);
+            auto flags_string = TRY_OR_DISCARD(flags_object.to_string(global_object));
-            if (vm.exception())
-                return {};
             if (!flags_string.contains("g")) {
                 vm.throw_exception<TypeError>(global_object, ErrorType::StringNonGlobalRegExp);
                 return {};
@@ -1021,10 +1010,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::replace_all)
 
         if (replace_value.is_function()) {
             auto result = TRY_OR_DISCARD(vm.call(replace_value.as_function(), js_undefined(), js_string(vm, search_string), Value(position), js_string(vm, string)));
-
+            replacement = TRY_OR_DISCARD(result.to_string(global_object));
-            replacement = result.to_string(global_object);
-            if (vm.exception())
-                return {};
         } else {
             replacement = TRY_OR_DISCARD(get_substitution(global_object, search_string.view(), string.view(), position, {}, js_undefined(), replace_value));
         }
@@ -1066,16 +1052,12 @@ static Value create_html(GlobalObject& global_object, Value string, const String
 {
     auto& vm = global_object.vm();
     TRY_OR_DISCARD(require_object_coercible(global_object, string));
-    auto str = string.to_string(global_object);
+    auto str = TRY_OR_DISCARD(string.to_string(global_object));
-    if (vm.exception())
-        return {};
     StringBuilder builder;
     builder.append('<');
     builder.append(tag);
     if (!attribute.is_empty()) {
-        auto value_string = value.to_string(global_object);
+        auto value_string = TRY_OR_DISCARD(value.to_string(global_object));
-        if (vm.exception())
-            return {};
         builder.append(' ');
         builder.append(attribute);
         builder.append("=\"");
@@ -1176,9 +1158,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::locale_compare)
     if (!string.has_value())
         return {};
 
-    auto that_string = vm.argument(0).to_string(global_object);
+    auto that_string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
 
     // FIXME: Actually compare the string not just according to their bits.
     if (string == that_string)

Userland/Libraries/LibJS/Runtime/SymbolConstructor.cpp

@@ -44,7 +44,7 @@ Value SymbolConstructor::call()
 {
     if (vm().argument(0).is_undefined())
         return js_symbol(heap(), {}, false);
-    return js_symbol(heap(), vm().argument(0).to_string(global_object()), false);
+    return js_symbol(heap(), TRY_OR_DISCARD(vm().argument(0).to_string(global_object())), false);
 }
 
 // 20.4.1.1 Symbol ( [ description ] ), https://tc39.es/ecma262/#sec-symbol-description
@@ -57,7 +57,7 @@ Value SymbolConstructor::construct(FunctionObject&)
 // 20.4.2.2 Symbol.for ( key ), https://tc39.es/ecma262/#sec-symbol.for
 JS_DEFINE_NATIVE_FUNCTION(SymbolConstructor::for_)
 {
-    String description = vm.argument(0).to_string(global_object);
+    auto description = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
     return global_object.vm().get_global_symbol(description);
 }
 

Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp

@@ -297,12 +297,8 @@ ThrowCompletionOr<Value> calendar_era(GlobalObject& global_object, Object& calen
     auto result = TRY(Value(&calendar).invoke(global_object, vm.names.era, &date_like));
 
     // 3. If result is not undefined, set result to ? ToString(result).
-    if (!result.is_undefined()) {
+    if (!result.is_undefined())
-        auto result_string = result.to_string(global_object);
+        result = js_string(vm, TRY(result.to_string(global_object)));
-        if (auto* exception = vm.exception())
-            return throw_completion(exception->value());
-        result = js_string(vm, move(result_string));
-    }
 
     // 4. Return result.
     return result;
@@ -362,9 +358,7 @@ ThrowCompletionOr<Object*> to_temporal_calendar(GlobalObject& global_object, Val
     }
 
     // 2. Let identifier be ? ToString(temporalCalendarLike).
-    auto identifier = temporal_calendar_like.to_string(global_object);
+    auto identifier = TRY(temporal_calendar_like.to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 3. If ! IsBuiltinCalendar(identifier) is false, then
     if (!is_builtin_calendar(identifier)) {
@@ -510,21 +504,15 @@ String format_calendar_annotation(StringView id, StringView show_calendar)
 // 12.1.28 CalendarEquals ( one, two ), https://tc39.es/proposal-temporal/#sec-temporal-calendarequals
 ThrowCompletionOr<bool> calendar_equals(GlobalObject& global_object, Object& one, Object& two)
 {
-    auto& vm = global_object.vm();
-
     // 1. If one and two are the same Object value, return true.
     if (&one == &two)
         return true;
 
     // 2. Let calendarOne be ? ToString(one).
-    auto calendar_one = Value(&one).to_string(global_object);
+    auto calendar_one = TRY(Value(&one).to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 3. Let calendarTwo be ? ToString(two).
-    auto calendar_two = Value(&two).to_string(global_object);
+    auto calendar_two = TRY(Value(&two).to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 4. If calendarOne is calendarTwo, return true.
     if (calendar_one == calendar_two)
@@ -543,14 +531,10 @@ ThrowCompletionOr<Object*> consolidate_calendars(GlobalObject& global_object, Ob
         return &two;
 
     // 2. Let calendarOne be ? ToString(one).
-    auto calendar_one = Value(&one).to_string(global_object);
+    auto calendar_one = TRY(Value(&one).to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 3. Let calendarTwo be ? ToString(two).
-    auto calendar_two = Value(&two).to_string(global_object);
+    auto calendar_two = TRY(Value(&two).to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 4. If calendarOne is calendarTwo, return two.
     if (calendar_one == calendar_two)

Userland/Libraries/LibJS/Runtime/Temporal/CalendarConstructor.cpp

@@ -49,9 +49,7 @@ Value CalendarConstructor::construct(FunctionObject& new_target)
     auto& global_object = this->global_object();
 
     // 2. Set id to ? ToString(id).
-    auto identifier = vm.argument(0).to_string(global_object);
+    auto identifier = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
 
     // 3. If ! IsBuiltinCalendar(id) is false, then
     if (!is_builtin_calendar(identifier)) {

Userland/Libraries/LibJS/Runtime/Temporal/CalendarPrototype.cpp

@@ -69,7 +69,7 @@ JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::id_getter)
     auto calendar = vm.this_value(global_object);
 
     // 2. Return ? ToString(calendar).
-    return js_string(vm, calendar.to_string(global_object));
+    return js_string(vm, TRY_OR_DISCARD(calendar.to_string(global_object)));
 }
 
 // 12.4.4 Temporal.Calendar.prototype.dateFromFields ( fields [ , options ] ), https://tc39.es/proposal-temporal/#sec-temporal.calendar.prototype.datefromfields
@@ -637,7 +637,7 @@ JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::to_json)
     auto calendar = vm.this_value(global_object);
 
     // 2. Return ? ToString(calendar).
-    return js_string(vm, calendar.to_string(global_object));
+    return js_string(vm, TRY_OR_DISCARD(calendar.to_string(global_object)));
 }
 
 // 15.6.2.6 Temporal.Calendar.prototype.era ( temporalDateLike ), https://tc39.es/proposal-temporal/#sec-temporal.calendar.prototype.era

Userland/Libraries/LibJS/Runtime/Temporal/Duration.cpp

@@ -34,8 +34,6 @@ Duration::Duration(double years, double months, double weeks, double days, doubl
 // 7.5.1 ToTemporalDuration ( item ), https://tc39.es/proposal-temporal/#sec-temporal-totemporalduration
 ThrowCompletionOr<Duration*> to_temporal_duration(GlobalObject& global_object, Value item)
 {
-    auto& vm = global_object.vm();
-
     TemporalDuration result;
 
     // 1. If Type(item) is Object, then
@@ -51,9 +49,7 @@ ThrowCompletionOr<Duration*> to_temporal_duration(GlobalObject& global_object, V
     // 2. Else,
     else {
         // a. Let string be ? ToString(item).
-        auto string = item.to_string(global_object);
+        auto string = TRY(item.to_string(global_object));
-        if (auto* exception = vm.exception())
-            return throw_completion(exception->value());
 
         // b. Let result be ? ParseTemporalDurationString(string).
         result = TRY(parse_temporal_duration_string(global_object, string));
@@ -451,9 +447,7 @@ ThrowCompletionOr<TemporalDuration> to_limited_temporal_duration(GlobalObject& g
     // 1. If Type(temporalDurationLike) is not Object, then
     if (!temporal_duration_like.is_object()) {
         // a. Let str be ? ToString(temporalDurationLike).
-        auto str = temporal_duration_like.to_string(global_object);
+        auto str = TRY(temporal_duration_like.to_string(global_object));
-        if (auto* exception = vm.exception())
-            return throw_completion(exception->value());
 
         // b. Let duration be ? ParseTemporalDurationString(str).
         duration = TRY(parse_temporal_duration_string(global_object, str));

Userland/Libraries/LibJS/Runtime/Temporal/Instant.cpp

@@ -72,8 +72,6 @@ ThrowCompletionOr<Instant*> create_temporal_instant(GlobalObject& global_object,
 // 8.5.3 ToTemporalInstant ( item ), https://tc39.es/proposal-temporal/#sec-temporal-totemporalinstant
 ThrowCompletionOr<Instant*> to_temporal_instant(GlobalObject& global_object, Value item)
 {
-    auto& vm = global_object.vm();
-
     // 1. If Type(item) is Object, then
     if (item.is_object()) {
         // a. If item has an [[InitializedTemporalInstant]] internal slot, then
@@ -92,9 +90,7 @@ ThrowCompletionOr<Instant*> to_temporal_instant(GlobalObject& global_object, Val
     }
 
     // 2. Let string be ? ToString(item).
-    auto string = item.to_string(global_object);
+    auto string = TRY(item.to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 3. Let epochNanoseconds be ? ParseTemporalInstant(string).
     auto* epoch_nanoseconds = TRY(parse_temporal_instant(global_object, string));

Userland/Libraries/LibJS/Runtime/Temporal/PlainDate.cpp

@@ -125,9 +125,7 @@ ThrowCompletionOr<PlainDate*> to_temporal_date(GlobalObject& global_object, Valu
     (void)TRY(to_temporal_overflow(global_object, *options));
 
     // 5. Let string be ? ToString(item).
-    auto string = item.to_string(global_object);
+    auto string = TRY(item.to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 6. Let result be ? ParseTemporalDateString(string).
     auto result = TRY(parse_temporal_date_string(global_object, string));
@@ -516,8 +514,6 @@ String pad_iso_year(i32 y)
 // 3.5.8 TemporalDateToString ( temporalDate, showCalendar ), https://tc39.es/proposal-temporal/#sec-temporal-temporaldatetostring
 ThrowCompletionOr<String> temporal_date_to_string(GlobalObject& global_object, PlainDate& temporal_date, StringView show_calendar)
 {
-    auto& vm = global_object.vm();
-
     // 1. Assert: Type(temporalDate) is Object.
     // 2. Assert: temporalDate has an [[InitializedTemporalDate]] internal slot.
 
@@ -531,9 +527,7 @@ ThrowCompletionOr<String> temporal_date_to_string(GlobalObject& global_object, P
     auto day = String::formatted("{:02}", temporal_date.iso_day());
 
     // 6. Let calendarID be ? ToString(temporalDate.[[Calendar]]).
-    auto calendar_id = Value(&temporal_date.calendar()).to_string(global_object);
+    auto calendar_id = TRY(Value(&temporal_date.calendar()).to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 7. Let calendar be ! FormatCalendarAnnotation(calendarID, showCalendar).
     auto calendar = format_calendar_annotation(calendar_id, show_calendar);

Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTime.cpp

@@ -187,9 +187,7 @@ ThrowCompletionOr<PlainDateTime*> to_temporal_date_time(GlobalObject& global_obj
         (void)TRY(to_temporal_overflow(global_object, *options));
 
         // b. Let string be ? ToString(item).
-        auto string = item.to_string(global_object);
+        auto string = TRY(item.to_string(global_object));
-        if (auto* exception = vm.exception())
-            return throw_completion(exception->value());
 
         // c. Let result be ? ParseTemporalDateTimeString(string).
         result = TRY(parse_temporal_date_time_string(global_object, string));
@@ -273,8 +271,6 @@ ThrowCompletionOr<PlainDateTime*> create_temporal_date_time(GlobalObject& global
 // 5.5.7 TemporalDateTimeToString ( isoYear, isoMonth, isoDay, hour, minute, second, millisecond, microsecond, nanosecond, calendar, precision, showCalendar ), , https://tc39.es/proposal-temporal/#sec-temporal-temporaldatetimetostring
 ThrowCompletionOr<String> temporal_date_time_to_string(GlobalObject& global_object, i32 iso_year, u8 iso_month, u8 iso_day, u8 hour, u8 minute, u8 second, u16 millisecond, u16 microsecond, u16 nanosecond, Value calendar, Variant<StringView, u8> const& precision, StringView show_calendar)
 {
-    auto& vm = global_object.vm();
-
     // 1. Assert: isoYear, isoMonth, isoDay, hour, minute, second, millisecond, microsecond, and nanosecond are integers.
 
     // 2. Let year be ! PadISOYear(isoYear).
@@ -287,9 +283,7 @@ ThrowCompletionOr<String> temporal_date_time_to_string(GlobalObject& global_obje
     auto seconds = format_seconds_string_part(second, millisecond, microsecond, nanosecond, precision);
 
     // 8. Let calendarID be ? ToString(calendar).
-    auto calendar_id = calendar.to_string(global_object);
+    auto calendar_id = TRY(calendar.to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 9. Let calendarString be ! FormatCalendarAnnotation(calendarID, showCalendar).
     auto calendar_string = format_calendar_annotation(calendar_id, show_calendar);

Userland/Libraries/LibJS/Runtime/Temporal/PlainMonthDay.cpp

@@ -154,8 +154,6 @@ ThrowCompletionOr<PlainMonthDay*> create_temporal_month_day(GlobalObject& global
 // 10.5.3 TemporalMonthDayToString ( monthDay, showCalendar ), https://tc39.es/proposal-temporal/#sec-temporal-temporalmonthdaytostring
 ThrowCompletionOr<String> temporal_month_day_to_string(GlobalObject& global_object, PlainMonthDay& month_day, StringView show_calendar)
 {
-    auto& vm = global_object.vm();
-
     // 1. Assert: Type(monthDay) is Object.
     // 2. Assert: monthDay has an [[InitializedTemporalMonthDay]] internal slot.
 
@@ -165,9 +163,7 @@ ThrowCompletionOr<String> temporal_month_day_to_string(GlobalObject& global_obje
     auto result = String::formatted("{:02}-{:02}", month_day.iso_month(), month_day.iso_day());
 
     // 6. Let calendarID be ? ToString(monthDay.[[Calendar]]).
-    auto calendar_id = Value(&month_day.calendar()).to_string(global_object);
+    auto calendar_id = TRY(Value(&month_day.calendar()).to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 7. If calendarID is not "iso8601", then
     if (calendar_id != "iso8601"sv) {

Userland/Libraries/LibJS/Runtime/Temporal/PlainTime.cpp

@@ -84,9 +84,7 @@ ThrowCompletionOr<PlainTime*> to_temporal_time(GlobalObject& global_object, Valu
         auto* calendar = TRY(get_temporal_calendar_with_iso_default(global_object, item_object));
 
         // e. If ? ToString(calendar) is not "iso8601", then
-        auto calendar_identifier = Value(calendar).to_string(global_object);
+        auto calendar_identifier = TRY(Value(calendar).to_string(global_object));
-        if (auto* exception = vm.exception())
-            return throw_completion(exception->value());
         if (calendar_identifier != "iso8601"sv) {
             // i. Throw a RangeError exception.
             return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidCalendarIdentifier, calendar_identifier);
@@ -101,9 +99,7 @@ ThrowCompletionOr<PlainTime*> to_temporal_time(GlobalObject& global_object, Valu
     // 4. Else,
     else {
         // a. Let string be ? ToString(item).
-        auto string = item.to_string(global_object);
+        auto string = TRY(item.to_string(global_object));
-        if (auto* exception = vm.exception())
-            return throw_completion(exception->value());
 
         // b. Let result be ? ParseTemporalTimeString(string).
         result = TRY(parse_temporal_time_string(global_object, string));

Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonth.cpp

@@ -68,9 +68,7 @@ ThrowCompletionOr<PlainYearMonth*> to_temporal_year_month(GlobalObject& global_o
     (void)TRY(to_temporal_overflow(global_object, *options));
 
     // 5. Let string be ? ToString(item).
-    auto string = item.to_string(global_object);
+    auto string = TRY(item.to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 6. Let result be ? ParseTemporalYearMonthString(string).
     auto result = TRY(parse_temporal_year_month_string(global_object, string));
@@ -236,8 +234,6 @@ ThrowCompletionOr<PlainYearMonth*> create_temporal_year_month(GlobalObject& glob
 // 9.5.8 TemporalYearMonthToString ( yearMonth, showCalendar ), https://tc39.es/proposal-temporal/#sec-temporal-temporalyearmonthtostring
 ThrowCompletionOr<String> temporal_year_month_to_string(GlobalObject& global_object, PlainYearMonth& year_month, StringView show_calendar)
 {
-    auto& vm = global_object.vm();
-
     // 1. Assert: Type(yearMonth) is Object.
     // 2. Assert: yearMonth has an [[InitializedTemporalYearMonth]] internal slot.
 
@@ -247,9 +243,7 @@ ThrowCompletionOr<String> temporal_year_month_to_string(GlobalObject& global_obj
     auto result = String::formatted("{}-{:02}", pad_iso_year(year_month.iso_year()), year_month.iso_month());
 
     // 6. Let calendarID be ? ToString(yearMonth.[[Calendar]]).
-    auto calendar_id = Value(&year_month.calendar()).to_string(global_object);
+    auto calendar_id = TRY(Value(&year_month.calendar()).to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 7. If calendarID is not "iso8601", then
     if (calendar_id != "iso8601") {

Userland/Libraries/LibJS/Runtime/Temporal/TimeZone.cpp

@@ -338,9 +338,7 @@ ThrowCompletionOr<Object*> to_temporal_time_zone(GlobalObject& global_object, Va
     }
 
     // 2. Let identifier be ? ToString(temporalTimeZoneLike).
-    auto identifier = temporal_time_zone_like.to_string(global_object);
+    auto identifier = TRY(temporal_time_zone_like.to_string(global_object));
-    if (auto* exception = vm.exception())
-        return throw_completion(exception->value());
 
     // 3. Let result be ? ParseTemporalTimeZone(identifier).
     auto result = TRY(parse_temporal_time_zone(global_object, identifier));

Userland/Libraries/LibJS/Runtime/Temporal/TimeZoneConstructor.cpp

@@ -49,9 +49,7 @@ Value TimeZoneConstructor::construct(FunctionObject& new_target)
     auto& global_object = this->global_object();
 
     // 2. Set identifier to ? ToString(identifier).
-    auto identifier = vm.argument(0).to_string(global_object);
+    auto identifier = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
 
     String canonical;
 

Userland/Libraries/LibJS/Runtime/Temporal/TimeZonePrototype.cpp

@@ -45,7 +45,7 @@ JS_DEFINE_NATIVE_FUNCTION(TimeZonePrototype::id_getter)
     auto time_zone = vm.this_value(global_object);
 
     // 2. Return ? ToString(timeZone).
-    return js_string(vm, time_zone.to_string(global_object));
+    return js_string(vm, TRY_OR_DISCARD(time_zone.to_string(global_object)));
 }
 
 // 11.4.4 Temporal.TimeZone.prototype.getOffsetNanosecondsFor ( instant ), https://tc39.es/proposal-temporal/#sec-temporal.timezone.prototype.getoffsetnanosecondsfor
@@ -121,7 +121,7 @@ JS_DEFINE_NATIVE_FUNCTION(TimeZonePrototype::to_json)
     auto time_zone = vm.this_value(global_object);
 
     // 2. Return ? ToString(timeZone).
-    return js_string(vm, time_zone.to_string(global_object));
+    return js_string(vm, TRY_OR_DISCARD(time_zone.to_string(global_object)));
 }
 
 }

Userland/Libraries/LibJS/Runtime/TypedArrayPrototype.cpp

@@ -594,11 +594,8 @@ JS_DEFINE_NATIVE_FUNCTION(TypedArrayPrototype::join)
         return {};
     auto length = typed_array->array_length();
     String separator = ",";
-    if (!vm.argument(0).is_undefined()) {
+    if (!vm.argument(0).is_undefined())
-        separator = vm.argument(0).to_string(global_object);
+        separator = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
-            return {};
-    }
 
     StringBuilder builder;
     for (size_t i = 0; i < length; ++i) {
@@ -607,9 +604,7 @@ JS_DEFINE_NATIVE_FUNCTION(TypedArrayPrototype::join)
         auto value = TRY_OR_DISCARD(typed_array->get(i));
         if (value.is_nullish())
             continue;
-        auto string = value.to_string(global_object);
+        auto string = TRY_OR_DISCARD(value.to_string(global_object));
-        if (vm.exception())
-            return {};
         builder.append(string);
     }
 
@@ -1487,9 +1482,7 @@ JS_DEFINE_NATIVE_FUNCTION(TypedArrayPrototype::to_locale_string)
         if (value.is_nullish())
             continue;
         auto locale_string_result = TRY_OR_DISCARD(value.invoke(global_object, vm.names.toLocaleString));
-        auto string = locale_string_result.to_string(global_object);
+        auto string = TRY_OR_DISCARD(locale_string_result.to_string(global_object));
-        if (vm.exception())
-            return {};
         builder.append(string);
     }
     return js_string(vm, builder.to_string());

Userland/Libraries/LibJS/Runtime/Value.cpp

@@ -17,6 +17,7 @@
 #include <LibJS/Runtime/BigIntObject.h>
 #include <LibJS/Runtime/BooleanObject.h>
 #include <LibJS/Runtime/BoundFunction.h>
+#include <LibJS/Runtime/Completion.h>
 #include <LibJS/Runtime/Error.h>
 #include <LibJS/Runtime/FunctionObject.h>
 #include <LibJS/Runtime/GlobalObject.h>
@@ -326,22 +327,21 @@ PrimitiveString* Value::to_primitive_string(GlobalObject& global_object)
 {
     if (is_string())
         return &as_string();
-    auto string = to_string(global_object);
+    auto string = TRY_OR_DISCARD(to_string(global_object));
-    if (global_object.vm().exception())
-        return nullptr;
     return js_string(global_object.heap(), string);
 }
 
 // 7.1.17 ToString ( argument ), https://tc39.es/ecma262/#sec-tostring
-String Value::to_string(GlobalObject& global_object) const
+ThrowCompletionOr<String> Value::to_string(GlobalObject& global_object) const
 {
+    auto& vm = global_object.vm();
     switch (m_type) {
     case Type::Undefined:
-        return "undefined";
+        return { "undefined"sv };
     case Type::Null:
-        return "null";
+        return { "null"sv };
     case Type::Boolean:
-        return m_value.as_bool ? "true" : "false";
+        return { m_value.as_bool ? "true"sv : "false"sv };
     case Type::Int32:
         return String::number(m_value.as_i32);
     case Type::Double:
@@ -349,14 +349,13 @@ String Value::to_string(GlobalObject& global_object) const
     case Type::String:
         return m_value.as_string->string();
     case Type::Symbol:
-        global_object.vm().throw_exception<TypeError>(global_object, ErrorType::Convert, "symbol", "string");
+        return vm.throw_completion<TypeError>(global_object, ErrorType::Convert, "symbol", "string");
-        return {};
     case Type::BigInt:
         return m_value.as_bigint->big_integer().to_base(10);
     case Type::Object: {
         auto primitive_value = to_primitive(global_object, PreferredType::String);
-        if (global_object.vm().exception())
+        if (auto* exception = vm.exception())
-            return {};
+            return throw_completion(exception->value());
         return primitive_value.to_string(global_object);
     }
     default:
@@ -369,10 +368,7 @@ Utf16String Value::to_utf16_string(GlobalObject& global_object) const
     if (m_type == Type::String)
         return m_value.as_string->utf16_string();
 
-    auto utf8_string = to_string(global_object);
+    auto utf8_string = TRY_OR_DISCARD(to_string(global_object));
-    if (global_object.vm().exception())
-        return {};
-
     return Utf16String(utf8_string);
 }
 
@@ -596,7 +592,7 @@ StringOrSymbol Value::to_property_key(GlobalObject& global_object) const
         return {};
     if (key.is_symbol())
         return &key.as_symbol();
-    return key.to_string(global_object);
+    return TRY_OR_DISCARD(key.to_string(global_object));
 }
 
 i32 Value::to_i32_slow_case(GlobalObject& global_object) const
@@ -1100,12 +1096,8 @@ Value add(GlobalObject& global_object, Value lhs, Value rhs)
         }
     }
     if (lhs_primitive.is_string() || rhs_primitive.is_string()) {
-        auto lhs_string = lhs_primitive.to_string(global_object);
+        auto lhs_string = TRY_OR_DISCARD(lhs_primitive.to_string(global_object));
-        if (vm.exception())
+        auto rhs_string = TRY_OR_DISCARD(rhs_primitive.to_string(global_object));
-            return {};
-        auto rhs_string = rhs_primitive.to_string(global_object);
-        if (vm.exception())
-            return {};
         StringBuilder builder(lhs_string.length() + rhs_string.length());
         builder.append(lhs_string);
         builder.append(rhs_string);

Userland/Libraries/LibJS/Runtime/Value.h

@@ -303,7 +303,7 @@ public:
 
     u64 encoded() const { return m_value.encoded; }
 
-    String to_string(GlobalObject&) const;
+    ThrowCompletionOr<String> to_string(GlobalObject&) const;
     Utf16String to_utf16_string(GlobalObject&) const;
     PrimitiveString* to_primitive_string(GlobalObject&);
     Value to_primitive(GlobalObject&, PreferredType preferred_type = PreferredType::Default) const;

Userland/Libraries/LibWeb/Bindings/CSSNamespace.cpp

@@ -38,9 +38,7 @@ JS_DEFINE_NATIVE_FUNCTION(CSSNamespace::escape)
         return {};
     }
 
-    auto identifier = vm.argument(0).to_string(global_object);
+    auto identifier = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
 
     return JS::js_string(vm, Web::CSS::serialize_an_identifier(identifier));
 }
@@ -55,17 +53,13 @@ JS_DEFINE_NATIVE_FUNCTION(CSSNamespace::supports)
 
     if (vm.argument_count() >= 2) {
         // When the supports(property, value) method is invoked with two arguments property and value:
-        String property_name = vm.argument(0).to_string(global_object);
+        auto property_name = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
-            return {};
 
         // If property is an ASCII case-insensitive match for any defined CSS property that the UA supports,
         // and value successfully parses according to that property’s grammar, return true.
         auto property = CSS::property_id_from_string(property_name);
         if (property != CSS::PropertyID::Invalid) {
-            auto value_string = vm.argument(1).to_string(global_object);
+            auto value_string = TRY_OR_DISCARD(vm.argument(1).to_string(global_object));
-            if (vm.exception())
-                return {};
             if (parse_css_value({}, value_string, property))
                 return JS::Value(true);
         }
@@ -79,9 +73,7 @@ JS_DEFINE_NATIVE_FUNCTION(CSSNamespace::supports)
         return JS::Value(false);
     } else {
         // When the supports(conditionText) method is invoked with a single conditionText argument:
-        String supports_text = vm.argument(0).to_string(global_object);
+        auto supports_text = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
-            return {};
 
         // If conditionText, parsed and evaluated as a <supports-condition>, would return true, return true.
         if (auto supports = parse_css_supports({}, supports_text); supports && supports->matches())

Userland/Libraries/LibWeb/Bindings/CSSStyleDeclarationWrapperCustom.cpp

@@ -48,9 +48,7 @@ JS::ThrowCompletionOr<bool> CSSStyleDeclarationWrapper::internal_set(JS::Propert
     if (property_id == CSS::PropertyID::Invalid)
         return Base::internal_set(name, value, receiver);
 
-    auto css_text = value.to_string(global_object());
+    auto css_text = TRY(value.to_string(global_object()));
-    if (auto* exception = vm().exception())
-        return JS::throw_completion(exception->value());
 
     impl().set_property(property_id, css_text);
     return true;

Userland/Libraries/LibWeb/Bindings/LocationObject.cpp

@@ -53,9 +53,7 @@ JS_DEFINE_NATIVE_FUNCTION(LocationObject::href_getter)
 JS_DEFINE_NATIVE_FUNCTION(LocationObject::href_setter)
 {
     auto& window = static_cast<WindowObject&>(global_object);
-    auto new_href = vm.argument(0).to_string(global_object);
+    auto new_href = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto href_url = window.impl().associated_document().parse_url(new_href);
     if (!href_url.is_valid()) {
         vm.throw_exception<JS::URIError>(global_object, String::formatted("Invalid URL '{}'", new_href));
@@ -133,9 +131,7 @@ JS_DEFINE_NATIVE_FUNCTION(LocationObject::reload)
 JS_DEFINE_NATIVE_FUNCTION(LocationObject::replace)
 {
     auto& window = static_cast<WindowObject&>(global_object);
-    auto url = vm.argument(0).to_string(global_object);
+    auto url = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     // FIXME: This needs spec compliance work.
     window.impl().did_call_location_replace({}, move(url));
     return JS::js_undefined();

Userland/Libraries/LibWeb/Bindings/WindowObject.cpp

@@ -190,11 +190,8 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::alert)
     if (!impl)
         return {};
     String message = "";
-    if (vm.argument_count()) {
+    if (vm.argument_count())
-        message = vm.argument(0).to_string(global_object);
+        message = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
-            return {};
-    }
     impl->alert(message);
     return JS::js_undefined();
 }
@@ -205,11 +202,8 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::confirm)
     if (!impl)
         return {};
     String message = "";
-    if (!vm.argument(0).is_undefined()) {
+    if (!vm.argument(0).is_undefined())
-        message = vm.argument(0).to_string(global_object);
+        message = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
-            return {};
-    }
     return JS::Value(impl->confirm(message));
 }
 
@@ -220,16 +214,10 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::prompt)
         return {};
     String message = "";
     String default_ = "";
-    if (!vm.argument(0).is_undefined()) {
+    if (!vm.argument(0).is_undefined())
-        message = vm.argument(0).to_string(global_object);
+        message = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
+    if (!vm.argument(1).is_undefined())
-            return {};
+        default_ = TRY_OR_DISCARD(vm.argument(1).to_string(global_object));
-    }
-    if (!vm.argument(1).is_undefined()) {
-        default_ = vm.argument(1).to_string(global_object);
-        if (vm.exception())
-            return {};
-    }
     auto response = impl->prompt(message, default_);
     if (response.is_null())
         return JS::js_null();
@@ -252,9 +240,7 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::set_interval)
     if (vm.argument(0).is_function()) {
         callback = &vm.argument(0).as_function();
     } else {
-        auto script_source = vm.argument(0).to_string(global_object);
+        auto script_source = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
-            return {};
         // FIXME: This needs more work once we have a environment settings object.
         // The spec wants us to use a task for the "run function or script string" part,
         // using a NativeFunction for the latter is a workaround so that we can reuse the
@@ -293,9 +279,7 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::set_timeout)
     if (vm.argument(0).is_function()) {
         callback = &vm.argument(0).as_function();
     } else {
-        auto script_source = vm.argument(0).to_string(global_object);
+        auto script_source = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-        if (vm.exception())
-            return {};
         // FIXME: This needs more work once we have a environment settings object.
         // The spec wants us to use a task for the "run function or script string" part,
         // using a NativeFunction for the latter is a workaround so that we can reuse the
@@ -415,9 +399,7 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::atob)
         vm.throw_exception<JS::TypeError>(global_object, JS::ErrorType::BadArgCountOne, "atob");
         return {};
     }
-    auto string = vm.argument(0).to_string(global_object);
+    auto string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto decoded = decode_base64(StringView(string));
 
     // decode_base64() returns a byte string. LibJS uses UTF-8 for strings. Use Latin1Decoder to convert bytes 128-255 to UTF-8.
@@ -435,9 +417,7 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::btoa)
         vm.throw_exception<JS::TypeError>(global_object, JS::ErrorType::BadArgCountOne, "btoa");
         return {};
     }
-    auto string = vm.argument(0).to_string(global_object);
+    auto string = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
 
     Vector<u8> byte_string;
     byte_string.ensure_capacity(string.length());
@@ -593,9 +573,7 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::match_media)
     auto* impl = impl_from(vm, global_object);
     if (!impl)
         return {};
-    auto media = vm.argument(0).to_string(global_object);
+    auto media = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     return wrap(global_object, impl->match_media(move(media)));
 }
 
@@ -660,9 +638,7 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::scroll)
 
         auto behavior_string_value = TRY_OR_DISCARD(options->get("behavior"));
         if (!behavior_string_value.is_undefined())
-            behavior_string = behavior_string_value.to_string(global_object);
+            behavior_string = TRY_OR_DISCARD(behavior_string_value.to_string(global_object));
-        if (vm.exception())
-            return {};
         if (behavior_string != "smooth" && behavior_string != "auto") {
             vm.throw_exception<JS::TypeError>(global_object, "Behavior is not one of 'smooth' or 'auto'");
             return {};
@@ -737,9 +713,7 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::scroll_by)
     top = top + current_scroll_position.y();
 
     auto behavior_string_value = TRY_OR_DISCARD(options->get("behavior"));
-    auto behavior_string = behavior_string_value.is_undefined() ? "auto" : behavior_string_value.to_string(global_object);
+    auto behavior_string = behavior_string_value.is_undefined() ? "auto" : TRY_OR_DISCARD(behavior_string_value.to_string(global_object));
-    if (vm.exception())
-        return {};
     if (behavior_string != "smooth" && behavior_string != "auto") {
         vm.throw_exception<JS::TypeError>(global_object, "Behavior is not one of 'smooth' or 'auto'");
         return {};

Userland/Utilities/js.cpp

@@ -890,9 +890,7 @@ static bool parse_and_run(JS::Interpreter& interpreter, StringView const& source
 
 static JS::Value load_file_impl(JS::VM& vm, JS::GlobalObject& global_object)
 {
-    auto filename = vm.argument(0).to_string(global_object);
+    auto filename = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto file = Core::File::construct(filename);
     if (!file->open(Core::OpenMode::ReadOnly)) {
         vm.throw_exception<JS::Error>(global_object, String::formatted("Failed to open '{}': {}", filename, file->error_string()));
@@ -914,9 +912,7 @@ static JS::Value load_file_impl(JS::VM& vm, JS::GlobalObject& global_object)
 
 static JS::Value load_json_impl(JS::VM& vm, JS::GlobalObject& global_object)
 {
-    auto filename = vm.argument(0).to_string(global_object);
+    auto filename = TRY_OR_DISCARD(vm.argument(0).to_string(global_object));
-    if (vm.exception())
-        return {};
     auto file = Core::File::construct(filename);
     if (!file->open(Core::OpenMode::ReadOnly)) {
         vm.throw_exception<JS::Error>(global_object, String::formatted("Failed to open '{}': {}", filename, file->error_string()));