LibJS: RAII in js????

.prettierignore

@@ -2,3 +2,9 @@ Base/home/anon/Source/js
 Userland/Libraries/LibJS/Tests/invalid-lhs-in-assignment.js
 Userland/Libraries/LibJS/Tests/unicode-identifier-escape.js
 Userland/Libraries/LibJS/Tests/modules/failing.mjs
+
+# FIXME: Remove once prettier is updated to support using declarations.
+Userland/Libraries/LibJS/Tests/builtins/DisposableStack/DisposableStack.prototype.@@dispose.js
+Userland/Libraries/LibJS/Tests/modules/top-level-dispose.mjs
+Userland/Libraries/LibJS/Tests/using-declaration.js
+Userland/Libraries/LibJS/Tests/using-for-loops.js

Userland/Libraries/LibJS/AST.h

@@ -922,6 +922,8 @@ class ForStatement final : public IterationStatement {
     virtual Bytecode::CodeGenerationErrorOr<void> generate_labelled_evaluation(Bytecode::Generator&, Vector<DeprecatedFlyString> const&) const override;
 
 private:
+    Completion for_body_evaluation(Interpreter&, Vector<DeprecatedFlyString> const&, size_t per_iteration_bindings_size) const;
+
     RefPtr<ASTNode> m_init;
     RefPtr<Expression> m_test;
     RefPtr<Expression> m_update;
@@ -1719,6 +1721,29 @@ class VariableDeclaration final : public Declaration {
     NonnullRefPtrVector<VariableDeclarator> m_declarations;
 };
 
+class UsingDeclaration final : public Declaration {
+public:
+    UsingDeclaration(SourceRange source_range, NonnullRefPtrVector<VariableDeclarator> declarations)
+        : Declaration(move(source_range))
+        , m_declarations(move(declarations))
+    {
+    }
+
+    virtual Completion execute(Interpreter&) const override;
+    virtual void dump(int indent) const override;
+
+    virtual ThrowCompletionOr<void> for_each_bound_name(ThrowCompletionOrVoidCallback<DeprecatedFlyString const&>&& callback) const override;
+
+    virtual bool is_constant_declaration() const override { return true; };
+
+    virtual bool is_lexical_declaration() const override { return true; }
+
+    NonnullRefPtrVector<VariableDeclarator> const& declarations() const { return m_declarations; }
+
+private:
+    NonnullRefPtrVector<VariableDeclarator> m_declarations;
+};
+
 class ObjectProperty final : public ASTNode {
 public:
     enum class Type : u8 {

Userland/Libraries/LibJS/CMakeLists.txt

@@ -75,6 +75,9 @@ set(SOURCES
     Runtime/DateConstructor.cpp
     Runtime/DatePrototype.cpp
     Runtime/DeclarativeEnvironment.cpp
+    Runtime/DisposableStack.cpp
+    Runtime/DisposableStackConstructor.cpp
+    Runtime/DisposableStackPrototype.cpp
     Runtime/ECMAScriptFunctionObject.cpp
     Runtime/Environment.cpp
     Runtime/Error.cpp
@@ -193,6 +196,9 @@ set(SOURCES
     Runtime/StringIteratorPrototype.cpp
     Runtime/StringObject.cpp
     Runtime/StringPrototype.cpp
+    Runtime/SuppressedError.cpp
+    Runtime/SuppressedErrorConstructor.cpp
+    Runtime/SuppressedErrorPrototype.cpp
     Runtime/Symbol.cpp
     Runtime/SymbolConstructor.cpp
     Runtime/SymbolObject.cpp

Userland/Libraries/LibJS/Forward.h

@@ -27,6 +27,7 @@
     __JS_ENUMERATE(BooleanObject, boolean, BooleanPrototype, BooleanConstructor, void)                                                         \
     __JS_ENUMERATE(DataView, data_view, DataViewPrototype, DataViewConstructor, void)                                                          \
     __JS_ENUMERATE(Date, date, DatePrototype, DateConstructor, void)                                                                           \
+    __JS_ENUMERATE(DisposableStack, disposable_stack, DisposableStackPrototype, DisposableStackConstructor, void)                              \
     __JS_ENUMERATE(Error, error, ErrorPrototype, ErrorConstructor, void)                                                                       \
     __JS_ENUMERATE(FinalizationRegistry, finalization_registry, FinalizationRegistryPrototype, FinalizationRegistryConstructor, void)          \
     __JS_ENUMERATE(FunctionObject, function, FunctionPrototype, FunctionConstructor, void)                                                     \
@@ -39,6 +40,7 @@
     __JS_ENUMERATE(Set, set, SetPrototype, SetConstructor, void)                                                                               \
     __JS_ENUMERATE(ShadowRealm, shadow_realm, ShadowRealmPrototype, ShadowRealmConstructor, void)                                              \
     __JS_ENUMERATE(StringObject, string, StringPrototype, StringConstructor, void)                                                             \
+    __JS_ENUMERATE(SuppressedError, suppressed_error, SuppressedErrorPrototype, SuppressedErrorConstructor, void)                              \
     __JS_ENUMERATE(SymbolObject, symbol, SymbolPrototype, SymbolConstructor, void)                                                             \
     __JS_ENUMERATE(WeakMap, weak_map, WeakMapPrototype, WeakMapConstructor, void)                                                              \
     __JS_ENUMERATE(WeakRef, weak_ref, WeakRefPrototype, WeakRefConstructor, void)                                                              \
@@ -132,7 +134,8 @@
     __JS_ENUMERATE(unscopables, unscopables)                 \
     __JS_ENUMERATE(species, species)                         \
     __JS_ENUMERATE(toPrimitive, to_primitive)                \
-    __JS_ENUMERATE(toStringTag, to_string_tag)
+    __JS_ENUMERATE(toStringTag, to_string_tag)               \
+    __JS_ENUMERATE(dispose, dispose)
 
 #define JS_ENUMERATE_REGEXP_FLAGS                \
     __JS_ENUMERATE(hasIndices, has_indices, d)   \