LibJS: Convert create_mutable_binding() to ThrowCompletionOr

Also add spec step comments to it while we're here.

Userland/Libraries/LibJS/AST.cpp

@@ -545,7 +545,7 @@ Value ForStatement::execute(Interpreter& interpreter, GlobalObject& global_objec
                 if (declaration.declaration_kind() == DeclarationKind::Const) {
                     loop_environment->create_immutable_binding(global_object, name, true);
                 } else {
-                    loop_environment->create_mutable_binding(global_object, name, false);
+                    MUST(loop_environment->create_mutable_binding(global_object, name, false));
                     let_declarations.append(name);
                 }
                 return IterationDecision::Continue;
@@ -571,7 +571,7 @@ Value ForStatement::execute(Interpreter& interpreter, GlobalObject& global_objec
         VERIFY(outer);
         auto* this_iteration_env = new_declarative_environment(*outer);
         for (auto& name : let_declarations) {
-            this_iteration_env->create_mutable_binding(global_object, name, false);
+            MUST(this_iteration_env->create_mutable_binding(global_object, name, false));
             auto last_value = last_iteration_env->get_binding_value(global_object, name, true);
             if (auto* exception = interpreter.exception())
                 return throw_completion(exception->value());
@@ -685,7 +685,7 @@ struct ForInOfHeadState {
                 if (for_declaration.declaration_kind() == DeclarationKind::Const)
                     iteration_environment->create_immutable_binding(global_object, name, false);
                 else
-                    iteration_environment->create_mutable_binding(global_object, name, true);
+                    MUST(iteration_environment->create_mutable_binding(global_object, name, true));
             });
             interpreter.vm().running_execution_context().lexical_environment = iteration_environment;
 
@@ -766,7 +766,7 @@ static ThrowCompletionOr<ForInOfHeadState> for_in_of_head_execute(Interpreter& i
             state.lhs_kind = ForInOfHeadState::LexicalBinding;
             new_environment = new_declarative_environment(*interpreter.lexical_environment());
             variable_declaration.for_each_bound_name([&](auto const& name) {
-                new_environment->create_mutable_binding(global_object, name, false);
+                MUST(new_environment->create_mutable_binding(global_object, name, false));
             });
         }
 
@@ -2770,11 +2770,11 @@ Value TryStatement::execute(Interpreter& interpreter, GlobalObject& global_objec
 
             m_handler->parameter().visit(
                 [&](FlyString const& parameter) {
-                    catch_scope->create_mutable_binding(global_object, parameter, false);
+                    MUST(catch_scope->create_mutable_binding(global_object, parameter, false));
                 },
                 [&](NonnullRefPtr<BindingPattern> const& pattern) {
                     pattern->for_each_bound_name([&](auto& name) {
-                        catch_scope->create_mutable_binding(global_object, name, false);
+                        MUST(catch_scope->create_mutable_binding(global_object, name, false));
                     });
                 });
 
@@ -3191,7 +3191,7 @@ void ScopeNode::block_declaration_instantiation(GlobalObject& global_object, Env
                 environment->create_immutable_binding(global_object, name, true);
             } else {
                 if (!MUST(environment->has_binding(name)))
-                    environment->create_mutable_binding(global_object, name, false);
+                    MUST(environment->create_mutable_binding(global_object, name, false));
             }
         });
 
@@ -3329,7 +3329,7 @@ ThrowCompletionOr<void> Program::global_declaration_instantiation(Interpreter& i
             if (declaration.is_constant_declaration())
                 global_environment.create_immutable_binding(global_object, name, true);
             else
-                global_environment.create_mutable_binding(global_object, name, false);
+                (void)global_environment.create_mutable_binding(global_object, name, false);
 
             if (interpreter.exception())
                 return IterationDecision::Break;

Userland/Libraries/LibJS/Runtime/AbstractOperations.cpp

@@ -629,7 +629,7 @@ ThrowCompletionOr<void> eval_declaration_instantiation(VM& vm, GlobalObject& glo
                         return IterationDecision::Break;
                 } else {
                     if (!MUST(variable_environment->has_binding(function_name))) {
-                        variable_environment->create_mutable_binding(global_object, function_name, true);
+                        MUST(variable_environment->create_mutable_binding(global_object, function_name, true));
                         variable_environment->initialize_binding(global_object, function_name, js_undefined());
                         VERIFY(!vm.exception());
                     }
@@ -680,7 +680,7 @@ ThrowCompletionOr<void> eval_declaration_instantiation(VM& vm, GlobalObject& glo
             if (declaration.is_constant_declaration())
                 lexical_environment->create_immutable_binding(global_object, name, true);
             else
-                lexical_environment->create_mutable_binding(global_object, name, false);
+                (void)lexical_environment->create_mutable_binding(global_object, name, false);
             if (vm.exception())
                 return IterationDecision::Break;
             return IterationDecision::Continue;
@@ -703,9 +703,7 @@ ThrowCompletionOr<void> eval_declaration_instantiation(VM& vm, GlobalObject& glo
             auto binding_exists = MUST(variable_environment->has_binding(declaration.name()));
 
             if (!binding_exists) {
-                variable_environment->create_mutable_binding(global_object, declaration.name(), true);
-                if (auto* exception = vm.exception())
-                    return throw_completion(exception->value());
+                TRY(variable_environment->create_mutable_binding(global_object, declaration.name(), true));
                 variable_environment->initialize_binding(global_object, declaration.name(), function);
             } else {
                 variable_environment->set_mutable_binding(global_object, declaration.name(), function, false);
@@ -724,9 +722,7 @@ ThrowCompletionOr<void> eval_declaration_instantiation(VM& vm, GlobalObject& glo
             auto binding_exists = MUST(variable_environment->has_binding(var_name));
 
             if (!binding_exists) {
-                variable_environment->create_mutable_binding(global_object, var_name, true);
-                if (auto* exception = vm.exception())
-                    return throw_completion(exception->value());
+                TRY(variable_environment->create_mutable_binding(global_object, var_name, true));
                 variable_environment->initialize_binding(global_object, var_name, js_undefined());
                 if (auto* exception = vm.exception())
                     return throw_completion(exception->value());

Userland/Libraries/LibJS/Runtime/DeclarativeEnvironment.cpp

@@ -46,8 +46,9 @@ ThrowCompletionOr<bool> DeclarativeEnvironment::has_binding(FlyString const& nam
 }
 
 // 9.1.1.1.2 CreateMutableBinding ( N, D ), https://tc39.es/ecma262/#sec-declarative-environment-records-createmutablebinding-n-d
-void DeclarativeEnvironment::create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted)
+ThrowCompletionOr<void> DeclarativeEnvironment::create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted)
 {
+    // 2. Create a mutable binding in envRec for N and record that it is uninitialized. If D is true, record that the newly created binding may be deleted by a subsequent DeleteBinding call.
     m_bindings.append(Binding {
         .value = {},
         .strict = false,
@@ -56,7 +57,12 @@ void DeclarativeEnvironment::create_mutable_binding(GlobalObject&, FlyString con
         .initialized = false,
     });
     auto result = m_names.set(name, m_bindings.size() - 1);
+
+    // 1. Assert: envRec does not already have a binding for N.
     VERIFY(result == AK::HashSetResult::InsertedNewEntry);
+
+    // 3. Return NormalCompletion(empty).
+    return {};
 }
 
 // 9.1.1.1.3 CreateImmutableBinding ( N, S ), https://tc39.es/ecma262/#sec-declarative-environment-records-createimmutablebinding-n-s
@@ -93,7 +99,7 @@ void DeclarativeEnvironment::set_mutable_binding(GlobalObject& global_object, Fl
             global_object.vm().throw_exception<ReferenceError>(global_object, ErrorType::UnknownIdentifier, name);
             return;
         }
-        create_mutable_binding(global_object, name, true);
+        (void)create_mutable_binding(global_object, name, true);
         initialize_binding(global_object, name, value);
         return;
     }

Userland/Libraries/LibJS/Runtime/DeclarativeEnvironment.h

@@ -23,7 +23,7 @@ public:
     virtual ~DeclarativeEnvironment() override;
 
     virtual ThrowCompletionOr<bool> has_binding(FlyString const& name, Optional<size_t>* = nullptr) const override;
-    virtual void create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted) override;
+    virtual ThrowCompletionOr<void> create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted) override;
     virtual void create_immutable_binding(GlobalObject&, FlyString const& name, bool strict) override;
     virtual void initialize_binding(GlobalObject&, FlyString const& name, Value) override;
     virtual void set_mutable_binding(GlobalObject&, FlyString const& name, Value, bool strict) override;

Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp

@@ -360,7 +360,7 @@ ThrowCompletionOr<void> ECMAScriptFunctionObject::function_declaration_instantia
         if (MUST(environment->has_binding(parameter_name)))
             continue;
 
-        environment->create_mutable_binding(global_object(), parameter_name, false);
+        MUST(environment->create_mutable_binding(global_object(), parameter_name, false));
         if (has_duplicates)
             environment->initialize_binding(global_object(), parameter_name, js_undefined());
         VERIFY(!vm.exception());
@@ -376,7 +376,7 @@ ThrowCompletionOr<void> ECMAScriptFunctionObject::function_declaration_instantia
         if (is_strict_mode())
             environment->create_immutable_binding(global_object(), vm.names.arguments.as_string(), false);
         else
-            environment->create_mutable_binding(global_object(), vm.names.arguments.as_string(), false);
+            MUST(environment->create_mutable_binding(global_object(), vm.names.arguments.as_string(), false));
 
         environment->initialize_binding(global_object(), vm.names.arguments.as_string(), arguments_object);
         parameter_names.set(vm.names.arguments.as_string());
@@ -445,7 +445,7 @@ ThrowCompletionOr<void> ECMAScriptFunctionObject::function_declaration_instantia
         if (scope_body) {
             scope_body->for_each_var_declared_name([&](auto const& name) {
                 if (!parameter_names.contains(name) && instantiated_var_names.set(name) == AK::HashSetResult::InsertedNewEntry) {
-                    environment->create_mutable_binding(global_object(), name, false);
+                    MUST(environment->create_mutable_binding(global_object(), name, false));
                     environment->initialize_binding(global_object(), name, js_undefined());
                 }
             });
@@ -459,7 +459,7 @@ ThrowCompletionOr<void> ECMAScriptFunctionObject::function_declaration_instantia
             scope_body->for_each_var_declared_name([&](auto const& name) {
                 if (instantiated_var_names.set(name) != AK::HashSetResult::InsertedNewEntry)
                     return IterationDecision::Continue;
-                var_environment->create_mutable_binding(global_object(), name, false);
+                MUST(var_environment->create_mutable_binding(global_object(), name, false));
 
                 Value initial_value;
                 if (!parameter_names.contains(name) || function_names.contains(name))
@@ -482,8 +482,7 @@ ThrowCompletionOr<void> ECMAScriptFunctionObject::function_declaration_instantia
                 return IterationDecision::Continue;
             // The spec says 'initializedBindings' here but that does not exist and it then adds it to 'instantiatedVarNames' so it probably means 'instantiatedVarNames'.
             if (!instantiated_var_names.contains(function_name) && function_name != vm.names.arguments.as_string()) {
-                var_environment->create_mutable_binding(global_object(), function_name, false);
-                VERIFY(!vm.exception());
+                MUST(var_environment->create_mutable_binding(global_object(), function_name, false));
                 var_environment->initialize_binding(global_object(), function_name, js_undefined());
                 instantiated_var_names.set(function_name);
             }
@@ -527,7 +526,7 @@ ThrowCompletionOr<void> ECMAScriptFunctionObject::function_declaration_instantia
             if (declaration.is_constant_declaration())
                 lex_environment->create_immutable_binding(global_object(), name, true);
             else
-                lex_environment->create_mutable_binding(global_object(), name, false);
+                MUST(lex_environment->create_mutable_binding(global_object(), name, false));
             return IterationDecision::Continue;
         });
     });

Userland/Libraries/LibJS/Runtime/Environment.h

@@ -34,7 +34,7 @@ public:
     virtual Object* with_base_object() const { return nullptr; }
 
     virtual ThrowCompletionOr<bool> has_binding([[maybe_unused]] FlyString const& name, [[maybe_unused]] Optional<size_t>* out_index = nullptr) const { return false; }
-    virtual void create_mutable_binding(GlobalObject&, [[maybe_unused]] FlyString const& name, [[maybe_unused]] bool can_be_deleted) { }
+    virtual ThrowCompletionOr<void> create_mutable_binding(GlobalObject&, [[maybe_unused]] FlyString const& name, [[maybe_unused]] bool can_be_deleted) { return {}; }
     virtual void create_immutable_binding(GlobalObject&, [[maybe_unused]] FlyString const& name, [[maybe_unused]] bool strict) { }
     virtual void initialize_binding(GlobalObject&, [[maybe_unused]] FlyString const& name, Value) { }
     virtual void set_mutable_binding(GlobalObject&, [[maybe_unused]] FlyString const& name, Value, [[maybe_unused]] bool strict) { }

Userland/Libraries/LibJS/Runtime/GlobalEnvironment.cpp

@@ -52,13 +52,15 @@ ThrowCompletionOr<bool> GlobalEnvironment::has_binding(FlyString const& name, Op
 }
 
 // 9.1.1.4.2 CreateMutableBinding ( N, D ), https://tc39.es/ecma262/#sec-global-environment-records-createmutablebinding-n-d
-void GlobalEnvironment::create_mutable_binding(GlobalObject& global_object, FlyString const& name, bool can_be_deleted)
+ThrowCompletionOr<void> GlobalEnvironment::create_mutable_binding(GlobalObject& global_object, FlyString const& name, bool can_be_deleted)
 {
-    if (MUST(m_declarative_record->has_binding(name))) {
-        global_object.vm().throw_exception<TypeError>(global_object, ErrorType::FixmeAddAnErrorString);
-        return;
-    }
-    m_declarative_record->create_mutable_binding(global_object, name, can_be_deleted);
+    // 1. Let DclRec be envRec.[[DeclarativeRecord]].
+    // 2. If DclRec.HasBinding(N) is true, throw a TypeError exception.
+    if (MUST(m_declarative_record->has_binding(name)))
+        return vm().throw_completion<TypeError>(global_object, ErrorType::FixmeAddAnErrorString);
+
+    // 3. Return DclRec.CreateMutableBinding(N, D).
+    return m_declarative_record->create_mutable_binding(global_object, name, can_be_deleted);
 }
 
 // 9.1.1.4.3 CreateImmutableBinding ( N, S ), https://tc39.es/ecma262/#sec-global-environment-records-createimmutablebinding-n-s
@@ -179,8 +181,8 @@ void GlobalEnvironment::create_global_var_binding(FlyString const& name, bool ca
         return;
     auto extensible = extensible_or_error.release_value();
     if (!has_property && extensible) {
-        m_object_record->create_mutable_binding(m_object_record->global_object(), name, can_be_deleted);
-        if (vm.exception())
+        auto result = m_object_record->create_mutable_binding(m_object_record->global_object(), name, can_be_deleted);
+        if (result.is_error())
             return;
         m_object_record->initialize_binding(m_object_record->global_object(), name, js_undefined());
         if (vm.exception())

Userland/Libraries/LibJS/Runtime/GlobalEnvironment.h

@@ -20,7 +20,7 @@ public:
     virtual ThrowCompletionOr<Value> get_this_binding(GlobalObject&) const final;
 
     virtual ThrowCompletionOr<bool> has_binding(FlyString const& name, Optional<size_t>* = nullptr) const override;
-    virtual void create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted) override;
+    virtual ThrowCompletionOr<void> create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted) override;
     virtual void create_immutable_binding(GlobalObject&, FlyString const& name, bool strict) override;
     virtual void initialize_binding(GlobalObject&, FlyString const& name, Value) override;
     virtual void set_mutable_binding(GlobalObject&, FlyString const& name, Value, bool strict) override;

Userland/Libraries/LibJS/Runtime/ObjectEnvironment.cpp

@@ -60,11 +60,12 @@ ThrowCompletionOr<bool> ObjectEnvironment::has_binding(FlyString const& name, Op
 }
 
 // 9.1.1.2.2 CreateMutableBinding ( N, D ), https://tc39.es/ecma262/#sec-object-environment-records-createmutablebinding-n-d
-void ObjectEnvironment::create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted)
+ThrowCompletionOr<void> ObjectEnvironment::create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted)
 {
     // 1. Let bindingObject be envRec.[[BindingObject]].
     // 2. Return ? DefinePropertyOrThrow(bindingObject, N, PropertyDescriptor { [[Value]]: undefined, [[Writable]]: true, [[Enumerable]]: true, [[Configurable]]: D }).
-    MUST(m_binding_object.define_property_or_throw(name, { .value = js_undefined(), .writable = true, .enumerable = true, .configurable = can_be_deleted }));
+    TRY(m_binding_object.define_property_or_throw(name, { .value = js_undefined(), .writable = true, .enumerable = true, .configurable = can_be_deleted }));
+    return {};
 }
 
 // 9.1.1.2.3 CreateImmutableBinding ( N, S ), https://tc39.es/ecma262/#sec-object-environment-records-createimmutablebinding-n-s

Userland/Libraries/LibJS/Runtime/ObjectEnvironment.h

@@ -21,7 +21,7 @@ public:
     ObjectEnvironment(Object& binding_object, IsWithEnvironment, Environment* outer_environment);
 
     virtual ThrowCompletionOr<bool> has_binding(FlyString const& name, Optional<size_t>* = nullptr) const override;
-    virtual void create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted) override;
+    virtual ThrowCompletionOr<void> create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted) override;
     virtual void create_immutable_binding(GlobalObject&, FlyString const& name, bool strict) override;
     virtual void initialize_binding(GlobalObject&, FlyString const& name, Value) override;
     virtual void set_mutable_binding(GlobalObject&, FlyString const& name, Value, bool strict) override;