Implement Private Runtime Environments (#2929)

boa_ast/src/function/class.rs

@@ -538,9 +538,6 @@ impl VisitWith for ClassElement {
 pub struct PrivateName {
     /// The `[[Description]]` internal slot of the private name.
     description: Sym,
-
-    /// The indices of the private name are included to ensure that private names are unique.
-    pub(crate) indices: (usize, usize),
 }
 
 impl PrivateName {
@@ -548,10 +545,7 @@ impl PrivateName {
     #[inline]
     #[must_use]
     pub const fn new(description: Sym) -> Self {
-        Self {
-            description,
-            indices: (0, 0),
-        }
+        Self { description }
     }
 
     /// Get the description of the private name.

boa_ast/src/operations.rs

@@ -6,14 +6,18 @@ use core::ops::ControlFlow;
 use std::convert::Infallible;
 
 use boa_interner::{Interner, Sym};
-use rustc_hash::{FxHashMap, FxHashSet};
+use rustc_hash::FxHashSet;
 
 use crate::{
     declaration::{Binding, ExportDeclaration, ImportDeclaration, VarDeclaration, Variable},
-    expression::{access::SuperPropertyAccess, Await, Identifier, SuperCall, Yield},
+    expression::{
+        access::{PrivatePropertyAccess, SuperPropertyAccess},
+        operator::BinaryInPrivate,
+        Await, Identifier, SuperCall, Yield,
+    },
     function::{
         ArrowFunction, AsyncArrowFunction, AsyncFunction, AsyncGenerator, Class, ClassElement,
-        Function, Generator, PrivateName,
+        Function, Generator,
     },
     property::{MethodDefinition, PropertyDefinition},
     statement::{
@@ -21,7 +25,7 @@ use crate::{
         LabelledItem,
     },
     try_break,
-    visitor::{NodeRef, VisitWith, Visitor, VisitorMut},
+    visitor::{NodeRef, VisitWith, Visitor},
     Declaration, Expression, ModuleItem, Statement, StatementList, StatementListItem,
 };
 
@@ -835,108 +839,105 @@ pub fn top_level_var_declared_names(stmts: &StatementList) -> FxHashSet<Identifi
     names
 }
 
-/// Resolves the private names of a class and all of the contained classes and private identifiers.
-pub fn class_private_name_resolver(node: &mut Class, top_level_class_index: usize) -> bool {
-    /// Visitor used by the function to search for an identifier with the name `arguments`.
-    #[derive(Debug, Clone)]
-    struct ClassPrivateNameResolver {
-        private_environments_stack: Vec<FxHashMap<Sym, PrivateName>>,
-        top_level_class_index: usize,
-    }
+/// Returns `true` if all private identifiers in a node are valid.
+///
+/// This is equivalent to the [`AllPrivateIdentifiersValid`][spec] syntax operation in the spec.
+///
+/// [spec]: https://tc39.es/ecma262/#sec-static-semantics-allprivateidentifiersvalid
+#[must_use]
+#[inline]
+pub fn all_private_identifiers_valid<'a, N>(node: &'a N, private_names: Vec<Sym>) -> bool
+where
+    &'a N: Into<NodeRef<'a>>,
+{
+    AllPrivateIdentifiersValidVisitor(private_names)
+        .visit(node.into())
+        .is_continue()
+}
 
-    impl<'ast> VisitorMut<'ast> for ClassPrivateNameResolver {
-        type BreakTy = ();
+struct AllPrivateIdentifiersValidVisitor(Vec<Sym>);
 
-        #[inline]
-        fn visit_class_mut(&mut self, node: &'ast mut Class) -> ControlFlow<Self::BreakTy> {
-            let mut names = FxHashMap::default();
-
-            for element in node.elements.iter_mut() {
-                match element {
-                    ClassElement::PrivateMethodDefinition(name, _)
-                    | ClassElement::PrivateStaticMethodDefinition(name, _)
-                    | ClassElement::PrivateFieldDefinition(name, _)
-                    | ClassElement::PrivateStaticFieldDefinition(name, _) => {
-                        name.indices = (
-                            self.top_level_class_index,
-                            self.private_environments_stack.len(),
-                        );
-                        names.insert(name.description(), *name);
-                    }
-                    _ => {}
+impl<'ast> Visitor<'ast> for AllPrivateIdentifiersValidVisitor {
+    type BreakTy = ();
+
+    fn visit_class(&mut self, node: &'ast Class) -> ControlFlow<Self::BreakTy> {
+        if let Some(node) = node.super_ref() {
+            try_break!(self.visit(node));
+        }
+
+        let mut names = self.0.clone();
+        for element in node.elements() {
+            match element {
+                ClassElement::PrivateMethodDefinition(name, _)
+                | ClassElement::PrivateStaticMethodDefinition(name, _)
+                | ClassElement::PrivateFieldDefinition(name, _)
+                | ClassElement::PrivateStaticFieldDefinition(name, _) => {
+                    names.push(name.description());
                 }
+                _ => {}
             }
+        }
 
-            self.private_environments_stack.push(names);
+        let mut visitor = Self(names);
 
-            for element in node.elements.iter_mut() {
-                match element {
-                    ClassElement::MethodDefinition(name, method)
-                    | ClassElement::StaticMethodDefinition(name, method) => {
-                        try_break!(self.visit_property_name_mut(name));
-                        try_break!(self.visit_method_definition_mut(method));
-                    }
-                    ClassElement::PrivateMethodDefinition(_, method)
-                    | ClassElement::PrivateStaticMethodDefinition(_, method) => {
-                        try_break!(self.visit_method_definition_mut(method));
-                    }
-                    ClassElement::FieldDefinition(name, expression)
-                    | ClassElement::StaticFieldDefinition(name, expression) => {
-                        try_break!(self.visit_property_name_mut(name));
-                        if let Some(expression) = expression {
-                            try_break!(self.visit_expression_mut(expression));
-                        }
-                    }
-                    ClassElement::PrivateFieldDefinition(_, expression)
-                    | ClassElement::PrivateStaticFieldDefinition(_, expression) => {
-                        if let Some(expression) = expression {
-                            try_break!(self.visit_expression_mut(expression));
-                        }
+        if let Some(node) = node.constructor() {
+            try_break!(visitor.visit(node));
+        }
+
+        for element in node.elements() {
+            match element {
+                ClassElement::MethodDefinition(name, method)
+                | ClassElement::StaticMethodDefinition(name, method) => {
+                    try_break!(visitor.visit(name));
+                    try_break!(visitor.visit(method));
+                }
+                ClassElement::FieldDefinition(name, expression)
+                | ClassElement::StaticFieldDefinition(name, expression) => {
+                    try_break!(visitor.visit(name));
+                    if let Some(expression) = expression {
+                        try_break!(visitor.visit(expression));
                     }
-                    ClassElement::StaticBlock(statement_list) => {
-                        try_break!(self.visit_statement_list_mut(statement_list));
+                }
+                ClassElement::PrivateMethodDefinition(_, method)
+                | ClassElement::PrivateStaticMethodDefinition(_, method) => {
+                    try_break!(visitor.visit(method));
+                }
+                ClassElement::PrivateFieldDefinition(_, expression)
+                | ClassElement::PrivateStaticFieldDefinition(_, expression) => {
+                    if let Some(expression) = expression {
+                        try_break!(visitor.visit(expression));
                     }
                 }
+                ClassElement::StaticBlock(statement_list) => {
+                    try_break!(visitor.visit(statement_list));
+                }
             }
-
-            if let Some(function) = &mut node.constructor {
-                try_break!(self.visit_function_mut(function));
-            }
-
-            self.private_environments_stack.pop();
-
-            ControlFlow::Continue(())
         }
 
-        #[inline]
-        fn visit_private_name_mut(
-            &mut self,
-            node: &'ast mut PrivateName,
-        ) -> ControlFlow<Self::BreakTy> {
-            let mut found = false;
-
-            for environment in self.private_environments_stack.iter().rev() {
-                if let Some(n) = environment.get(&node.description()) {
-                    found = true;
-                    node.indices = n.indices;
-                    break;
-                }
-            }
+        ControlFlow::Continue(())
+    }
 
-            if found {
-                ControlFlow::Continue(())
-            } else {
-                ControlFlow::Break(())
-            }
+    fn visit_private_property_access(
+        &mut self,
+        node: &'ast PrivatePropertyAccess,
+    ) -> ControlFlow<Self::BreakTy> {
+        if self.0.contains(&node.field().description()) {
+            self.visit(node.target())
+        } else {
+            ControlFlow::Break(())
         }
     }
 
-    let mut visitor = ClassPrivateNameResolver {
-        private_environments_stack: Vec::new(),
-        top_level_class_index,
-    };
-
-    visitor.visit_class_mut(node).is_continue()
+    fn visit_binary_in_private(
+        &mut self,
+        node: &'ast BinaryInPrivate,
+    ) -> ControlFlow<Self::BreakTy> {
+        if self.0.contains(&node.lhs().description()) {
+            self.visit(node.rhs())
+        } else {
+            ControlFlow::Break(())
+        }
+    }
 }
 
 /// Errors that can occur when checking labels.

boa_engine/src/builtins/function/mod.rs

@@ -12,15 +12,15 @@
 //! [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function
 
 use crate::{
-    builtins::BuiltInObject,
+    builtins::{BuiltInBuilder, BuiltInConstructor, BuiltInObject, IntrinsicObject},
     bytecompiler::FunctionCompiler,
     context::intrinsics::{Intrinsics, StandardConstructor, StandardConstructors},
-    environments::EnvironmentStack,
+    environments::{EnvironmentStack, PrivateEnvironment},
     error::JsNativeError,
     js_string,
     native_function::NativeFunction,
     object::{internal_methods::get_prototype_from_constructor, JsObject, Object, ObjectData},
-    object::{JsFunction, PrivateElement},
+    object::{JsFunction, PrivateElement, PrivateName},
     property::{Attribute, PropertyDescriptor, PropertyKey},
     realm::Realm,
     string::utf16,
@@ -30,21 +30,22 @@ use crate::{
     Context, JsArgs, JsResult, JsString, JsValue,
 };
 use boa_ast::{
-    function::{FormalParameterList, PrivateName},
-    operations::{bound_names, contains, lexically_declared_names, ContainsSymbol},
+    function::FormalParameterList,
+    operations::{
+        all_private_identifiers_valid, bound_names, contains, lexically_declared_names,
+        ContainsSymbol,
+    },
     StatementList,
 };
 use boa_gc::{self, custom_trace, Finalize, Gc, Trace};
 use boa_interner::Sym;
 use boa_parser::{Parser, Source};
 use boa_profiler::Profiler;
-use thin_vec::ThinVec;
-
 use std::{fmt, io::Read};
-
-use super::{BuiltInBuilder, BuiltInConstructor, IntrinsicObject};
+use thin_vec::ThinVec;
 
 pub(crate) mod arguments;
+
 #[cfg(test)]
 mod tests;
 
@@ -308,6 +309,13 @@ impl Function {
         Self { kind, realm }
     }
 
+    /// Push a private environment to the function.
+    pub(crate) fn push_private_environment(&mut self, environment: Gc<PrivateEnvironment>) {
+        if let FunctionKind::Ordinary { environments, .. } = &mut self.kind {
+            environments.push_private(environment);
+        }
+    }
+
     /// Returns true if the function object is a derived constructor.
     pub(crate) const fn is_derived_constructor(&self) -> bool {
         if let FunctionKind::Ordinary {
@@ -368,9 +376,9 @@ impl Function {
     }
 
     /// Pushes a private value to the `[[Fields]]` internal slot if present.
-    pub(crate) fn push_field_private(&mut self, key: PrivateName, value: JsFunction) {
+    pub(crate) fn push_field_private(&mut self, name: PrivateName, value: JsFunction) {
         if let FunctionKind::Ordinary { fields, .. } = &mut self.kind {
-            fields.push(ClassFieldDefinition::Private(key, value));
+            fields.push(ClassFieldDefinition::Private(name, value));
         }
     }
 
@@ -705,6 +713,18 @@ impl BuiltInFunctionObject {
                 }
             }
 
+            if !all_private_identifiers_valid(&parameters, Vec::new()) {
+                return Err(JsNativeError::syntax()
+                    .with_message("invalid private identifier usage")
+                    .into());
+            }
+
+            if !all_private_identifiers_valid(&body, Vec::new()) {
+                return Err(JsNativeError::syntax()
+                    .with_message("invalid private identifier usage")
+                    .into());
+            }
+
             let code = FunctionCompiler::new()
                 .name(Sym::ANONYMOUS)
                 .generator(generator)

boa_engine/src/bytecompiler/class.rs

@@ -100,6 +100,23 @@ impl ByteCompiler<'_, '_> {
         self.emit_opcode(Opcode::SetClassPrototype);
         self.emit_opcode(Opcode::Swap);
 
+        let count_label = self.emit_opcode_with_operand(Opcode::PushPrivateEnvironment);
+        let mut count = 0;
+        for element in class.elements() {
+            match element {
+                ClassElement::PrivateMethodDefinition(name, _)
+                | ClassElement::PrivateStaticMethodDefinition(name, _)
+                | ClassElement::PrivateFieldDefinition(name, _)
+                | ClassElement::PrivateStaticFieldDefinition(name, _) => {
+                    count += 1;
+                    let index = self.get_or_insert_private_name(*name);
+                    self.emit_u32(index);
+                }
+                _ => {}
+            }
+        }
+        self.patch_jump_with_target(count_label, count);
+
         // TODO: set function name for getter and setters
         for element in class.elements() {
             match element {
@@ -536,6 +553,8 @@ impl ByteCompiler<'_, '_> {
             self.emit_opcode(Opcode::PopEnvironment);
         }
 
+        self.emit_opcode(Opcode::PopPrivateEnvironment);
+
         if !expression {
             self.emit_binding(
                 BindingOpcode::InitVar,

boa_engine/src/bytecompiler/declarations.rs

@@ -7,8 +7,9 @@ use boa_ast::{
     declaration::{Binding, LexicalDeclaration, VariableList},
     function::FormalParameterList,
     operations::{
-        bound_names, lexically_scoped_declarations, top_level_lexically_declared_names,
-        top_level_var_declared_names, top_level_var_scoped_declarations, VarScopedDeclaration,
+        all_private_identifiers_valid, bound_names, lexically_scoped_declarations,
+        top_level_lexically_declared_names, top_level_var_declared_names,
+        top_level_var_scoped_declarations, VarScopedDeclaration,
     },
     visitor::NodeRef,
     Declaration, StatementList, StatementListItem,
@@ -428,9 +429,17 @@ impl ByteCompiler<'_, '_> {
         // 5. Let pointer be privateEnv.
         // 6. Repeat, while pointer is not null,
         //     a. For each Private Name binding of pointer.[[Names]], do
-        //         i. If privateIdentifiers does not contain binding.[[Description]], append binding.[[Description]] to privateIdentifiers.
+        //         i. If privateIdentifiers does not contain binding.[[Description]],
+        //            append binding.[[Description]] to privateIdentifiers.
         //     b. Set pointer to pointer.[[OuterPrivateEnvironment]].
+        let private_identifiers = self.context.vm.environments.private_name_descriptions();
+
         // 7. If AllPrivateIdentifiersValid of body with argument privateIdentifiers is false, throw a SyntaxError exception.
+        if !all_private_identifiers_valid(body, private_identifiers) {
+            return Err(JsNativeError::syntax()
+                .with_message("invalid private identifier")
+                .into());
+        }
 
         // 8. Let functionsToInitialize be a new empty List.
         let mut functions_to_initialize = Vec::new();

boa_engine/src/environments/mod.rs

@@ -31,7 +31,7 @@ pub(crate) use {
     compile::CompileTimeEnvironment,
     runtime::{
         BindingLocator, DeclarativeEnvironment, Environment, EnvironmentStack, FunctionSlots,
-        ThisBindingStatus,
+        PrivateEnvironment, ThisBindingStatus,
     },
 };
 

boa_engine/src/environments/runtime/mod.rs

@@ -1,17 +1,24 @@
 use crate::{
-    environments::CompileTimeEnvironment, error::JsNativeError, object::JsObject, Context,
-    JsResult, JsString, JsSymbol, JsValue,
+    environments::CompileTimeEnvironment,
+    error::JsNativeError,
+    object::{JsObject, PrivateName},
+    Context, JsResult, JsString, JsSymbol, JsValue,
 };
 use boa_ast::expression::Identifier;
 use boa_gc::{empty_trace, Finalize, Gc, GcRefCell, Trace};
+use boa_interner::Sym;
 use rustc_hash::FxHashSet;
 
 mod declarative;
+mod private;
 
 use self::declarative::ModuleEnvironment;
-pub(crate) use self::declarative::{
-    DeclarativeEnvironment, DeclarativeEnvironmentKind, FunctionEnvironment, FunctionSlots,
-    LexicalEnvironment, ThisBindingStatus,
+pub(crate) use self::{
+    declarative::{
+        DeclarativeEnvironment, DeclarativeEnvironmentKind, FunctionEnvironment, FunctionSlots,
+        LexicalEnvironment, ThisBindingStatus,
+    },
+    private::PrivateEnvironment,
 };
 
 /// The environment stack holds all environments at runtime.
@@ -21,6 +28,8 @@ pub(crate) use self::declarative::{
 #[derive(Clone, Debug, Trace, Finalize)]
 pub(crate) struct EnvironmentStack {
     stack: Vec<Environment>,
+
+    private_stack: Vec<Gc<PrivateEnvironment>>,
 }
 
 /// A runtime environment.
@@ -56,6 +65,7 @@ impl EnvironmentStack {
         ));
         Self {
             stack: vec![Environment::Declarative(global)],
+            private_stack: Vec::new(),
         }
     }
 
@@ -457,6 +467,51 @@ impl EnvironmentStack {
             env.set(binding_index, value);
         }
     }
+
+    /// Push a private environment to the private environment stack.
+    pub(crate) fn push_private(&mut self, environment: Gc<PrivateEnvironment>) {
+        self.private_stack.push(environment);
+    }
+
+    /// Pop a private environment from the private environment stack.
+    pub(crate) fn pop_private(&mut self) {
+        self.private_stack.pop();
+    }
+
+    /// `ResolvePrivateIdentifier ( privEnv, identifier )`
+    ///
+    /// More information:
+    ///  - [ECMAScript specification][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-resolve-private-identifier
+    pub(crate) fn resolve_private_identifier(&self, identifier: Sym) -> Option<PrivateName> {
+        // 1. Let names be privEnv.[[Names]].
+        // 2. For each Private Name pn of names, do
+        //     a. If pn.[[Description]] is identifier, then
+        //         i. Return pn.
+        // 3. Let outerPrivEnv be privEnv.[[OuterPrivateEnvironment]].
+        // 4. Assert: outerPrivEnv is not null.
+        // 5. Return ResolvePrivateIdentifier(outerPrivEnv, identifier).
+        for environment in self.private_stack.iter().rev() {
+            if environment.descriptions().contains(&identifier) {
+                return Some(PrivateName::new(identifier, environment.id()));
+            }
+        }
+        None
+    }
+
+    /// Return all private name descriptions in all private environments.
+    pub(crate) fn private_name_descriptions(&self) -> Vec<Sym> {
+        let mut names = Vec::new();
+        for environment in self.private_stack.iter().rev() {
+            for name in environment.descriptions() {
+                if !names.contains(name) {
+                    names.push(*name);
+                }
+            }
+        }
+        names
+    }
 }
 
 /// A binding locator contains all information about a binding that is needed to resolve it at runtime.

boa_engine/src/environments/runtime/private.rs

@@ -0,0 +1,34 @@
+use boa_gc::{empty_trace, Finalize, Trace};
+use boa_interner::Sym;
+
+/// Private runtime environment.
+#[derive(Clone, Debug, Finalize)]
+pub(crate) struct PrivateEnvironment {
+    /// The unique identifier of the private names.
+    id: usize,
+
+    /// The `[[Description]]` internal slot of the private names.
+    descriptions: Vec<Sym>,
+}
+
+// Safety: PrivateEnvironment does not contain any objects that need to be traced.
+unsafe impl Trace for PrivateEnvironment {
+    empty_trace!();
+}
+
+impl PrivateEnvironment {
+    /// Creates a new `PrivateEnvironment`.
+    pub(crate) fn new(id: usize, descriptions: Vec<Sym>) -> Self {
+        Self { id, descriptions }
+    }
+
+    /// Gets the id of this private environment.
+    pub(crate) const fn id(&self) -> usize {
+        self.id
+    }
+
+    /// Gets the descriptions of this private environment.
+    pub(crate) fn descriptions(&self) -> &[Sym] {
+        &self.descriptions
+    }
+}

boa_engine/src/object/jsobject.rs

@@ -5,7 +5,7 @@
 use super::{
     internal_methods::{InternalObjectMethods, ARRAY_EXOTIC_INTERNAL_METHODS},
     shape::{shared_shape::SharedShape, Shape},
-    JsPrototype, NativeObject, Object, PropertyMap,
+    JsPrototype, NativeObject, Object, PrivateName, PropertyMap,
 };
 use crate::{
     context::intrinsics::Intrinsics,
@@ -17,6 +17,7 @@ use crate::{
     Context, JsResult, JsValue,
 };
 use boa_gc::{self, Finalize, Gc, GcRefCell, Trace};
+use boa_interner::Sym;
 use std::{
     cell::RefCell,
     collections::HashMap,
@@ -944,6 +945,12 @@ Cannot both specify accessors and a value or writable attribute",
     pub(crate) const fn inner(&self) -> &Gc<VTableObject> {
         &self.inner
     }
+
+    /// Create a new private name with this object as the unique identifier.
+    pub(crate) fn private_name(&self, description: Sym) -> PrivateName {
+        let ptr: *const _ = self.as_ref();
+        PrivateName::new(description, ptr as usize)
+    }
 }
 
 impl AsRef<GcRefCell<Object>> for JsObject {

boa_engine/src/object/mod.rs

@@ -2,7 +2,7 @@
 //!
 //! For the builtin object wrappers, please see [`object::builtins`][builtins] for implementors.
 
-use boa_ast::function::PrivateName;
+use boa_interner::Sym;
 pub use jsobject::{RecursionLimiter, Ref, RefMut};
 pub use operations::IntegrityLevel;
 pub use property_map::*;
@@ -164,6 +164,23 @@ unsafe impl Trace for Object {
     });
 }
 
+/// A Private Name.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct PrivateName {
+    /// The `[[Description]]` internal slot of the private name.
+    description: Sym,
+
+    /// The unique identifier of the private name.
+    id: usize,
+}
+
+impl PrivateName {
+    /// Create a new private name.
+    pub(crate) const fn new(description: Sym, id: usize) -> Self {
+        Self { description, id }
+    }
+}
+
 /// The representation of private object elements.
 #[derive(Clone, Debug, Trace, Finalize)]
 pub enum PrivateElement {

boa_engine/src/object/operations.rs

@@ -2,16 +2,13 @@ use crate::{
     builtins::{function::ClassFieldDefinition, Array},
     context::intrinsics::{StandardConstructor, StandardConstructors},
     error::JsNativeError,
-    object::{JsObject, PrivateElement, PROTOTYPE},
+    object::{JsFunction, JsObject, PrivateElement, PrivateName, CONSTRUCTOR, PROTOTYPE},
     property::{PropertyDescriptor, PropertyDescriptorBuilder, PropertyKey, PropertyNameKind},
     realm::Realm,
     string::utf16,
     value::Type,
     Context, JsResult, JsSymbol, JsValue,
 };
-use boa_ast::function::PrivateName;
-
-use super::{JsFunction, CONSTRUCTOR};
 
 /// Object integrity level.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]

boa_engine/src/vm/code_block.rs

@@ -391,6 +391,11 @@ impl CodeBlock {
                     interner.resolve_expect(self.private_names[operand as usize].description()),
                 )
             }
+            Opcode::PushPrivateEnvironment => {
+                let count = self.read::<u32>(*pc);
+                *pc += size_of::<u32>() * (count as usize + 1);
+                String::new()
+            }
             Opcode::Pop
             | Opcode::PopIfThrown
             | Opcode::Dup
@@ -505,6 +510,7 @@ impl CodeBlock {
             | Opcode::PushObjectEnvironment
             | Opcode::IsObject
             | Opcode::SetNameByLocator
+            | Opcode::PopPrivateEnvironment
             | Opcode::Nop => String::new(),
         }
     }

boa_engine/src/vm/flowgraph/mod.rs

@@ -478,6 +478,12 @@ impl CodeBlock {
                         );
                     }
                 }
+                Opcode::PushPrivateEnvironment => {
+                    let count = self.read::<u32>(pc);
+                    pc += size_of::<u32>() * (count as usize + 1);
+                    graph.add_node(previous_pc, NodeShape::None, label.into(), Color::None);
+                    graph.add_edge(previous_pc, pc, None, Color::None, EdgeStyle::Line);
+                }
                 Opcode::Pop
                 | Opcode::PopIfThrown
                 | Opcode::Dup
@@ -588,7 +594,8 @@ impl CodeBlock {
                 | Opcode::IsObject
                 | Opcode::SetNameByLocator
                 | Opcode::Nop
-                | Opcode::PushObjectEnvironment => {
+                | Opcode::PushObjectEnvironment
+                | Opcode::PopPrivateEnvironment => {
                     graph.add_node(previous_pc, NodeShape::None, label.into(), Color::None);
                     graph.add_edge(previous_pc, pc, None, Color::None, EdgeStyle::Line);
                 }

boa_engine/src/vm/opcode/binary_ops/mod.rs

@@ -122,12 +122,18 @@ impl Operation for InPrivate {
                 ))
                 .into());
         };
+
+        let name = context
+            .vm
+            .environments
+            .resolve_private_identifier(name.description())
+            .expect("private name must be in environment");
+
         if rhs.private_element_find(&name, true, true).is_some() {
             context.vm.push(true);
         } else {
             context.vm.push(false);
         }
-
         Ok(CompletionType::Normal)
     }
 }

boa_engine/src/vm/opcode/get/private.rs

@@ -19,6 +19,13 @@ impl Operation for GetPrivateField {
         let name = context.vm.frame().code_block.private_names[index as usize];
         let value = context.vm.pop();
         let base_obj = value.to_object(context)?;
+
+        let name = context
+            .vm
+            .environments
+            .resolve_private_identifier(name.description())
+            .expect("private name must be in environment");
+
         let result = base_obj.private_get(&name, context)?;
         context.vm.push(result);
         Ok(CompletionType::Normal)

boa_engine/src/vm/opcode/mod.rs

@@ -1619,6 +1619,20 @@ generate_impl! {
         /// Stack: count * (cooked_value, raw_value) **=>** template
         TemplateCreate,
 
+        /// Push a private environment.
+        ///
+        /// Operands: count: `u32`, count * private_name_index: `u32`
+        ///
+        /// Stack: class **=>** class
+        PushPrivateEnvironment,
+
+        /// Pop a private environment.
+        ///
+        /// Operands:
+        ///
+        /// Stack: **=>**
+        PopPrivateEnvironment,
+
         /// No-operation instruction, does nothing.
         ///
         /// Operands:

boa_engine/src/vm/opcode/push/class/field.rs

@@ -74,12 +74,13 @@ impl Operation for PushClassFieldPrivate {
             .expect("class must be function object");
         field_function.set_home_object(class_object.clone());
         field_function.set_class_object(class_object.clone());
+
         class_object
             .borrow_mut()
             .as_function_mut()
             .expect("class must be function object")
             .push_field_private(
-                name,
+                class_object.private_name(name.description()),
                 JsFunction::from_object_unchecked(field_function_object.clone()),
             );
         Ok(CompletionType::Normal)

boa_engine/src/vm/opcode/push/class/private.rs

@@ -36,11 +36,15 @@ impl Operation for PushClassPrivateMethod {
 
         let class = context.vm.pop();
         let class_object = class.as_object().expect("class must be function object");
+
         class_object
             .borrow_mut()
             .as_function_mut()
             .expect("class must be function object")
-            .push_private_method(name, PrivateElement::Method(method_object.clone()));
+            .push_private_method(
+                class_object.private_name(name.description()),
+                PrivateElement::Method(method_object.clone()),
+            );
 
         let mut method_object_mut = method_object.borrow_mut();
         let function = method_object_mut
@@ -69,12 +73,13 @@ impl Operation for PushClassPrivateGetter {
         let getter_object = getter.as_callable().expect("getter must be callable");
         let class = context.vm.pop();
         let class_object = class.as_object().expect("class must be function object");
+
         class_object
             .borrow_mut()
             .as_function_mut()
             .expect("class must be function object")
             .push_private_method(
-                name,
+                class_object.private_name(name.description()),
                 PrivateElement::Accessor {
                     getter: Some(getter_object.clone()),
                     setter: None,
@@ -107,12 +112,13 @@ impl Operation for PushClassPrivateSetter {
         let setter_object = setter.as_callable().expect("getter must be callable");
         let class = context.vm.pop();
         let class_object = class.as_object().expect("class must be function object");
+
         class_object
             .borrow_mut()
             .as_function_mut()
             .expect("class must be function object")
             .push_private_method(
-                name,
+                class_object.private_name(name.description()),
                 PrivateElement::Accessor {
                     getter: None,
                     setter: Some(setter_object.clone()),

boa_engine/src/vm/opcode/push/environment.rs

@@ -1,7 +1,9 @@
 use crate::{
+    environments::PrivateEnvironment,
     vm::{opcode::Operation, CompletionType},
     Context, JsResult,
 };
+use boa_gc::Gc;
 
 /// `PushDeclarativeEnvironment` implements the Opcode Operation for `Opcode::PushDeclarativeEnvironment`
 ///
@@ -74,3 +76,60 @@ impl Operation for PushObjectEnvironment {
         Ok(CompletionType::Normal)
     }
 }
+
+/// `PushPrivateEnvironment` implements the Opcode Operation for `Opcode::PushPrivateEnvironment`
+///
+/// Operation:
+///  - Push a private environment.
+#[derive(Debug, Clone, Copy)]
+pub(crate) struct PushPrivateEnvironment;
+
+impl Operation for PushPrivateEnvironment {
+    const NAME: &'static str = "PushPrivateEnvironment";
+    const INSTRUCTION: &'static str = "INST - PushPrivateEnvironment";
+
+    fn execute(context: &mut Context<'_>) -> JsResult<CompletionType> {
+        let class_value = context.vm.pop();
+        let class = class_value.to_object(context)?;
+
+        let count = context.vm.read::<u32>();
+        let mut names = Vec::with_capacity(count as usize);
+        for _ in 0..count {
+            let index = context.vm.read::<u32>();
+            let name = context.vm.frame().code_block.private_names[index as usize];
+            names.push(name.description());
+        }
+
+        let ptr: *const _ = class.as_ref();
+        let environment = Gc::new(PrivateEnvironment::new(ptr as usize, names));
+
+        class
+            .borrow_mut()
+            .as_function_mut()
+            .expect("class object must be function")
+            .push_private_environment(environment.clone());
+        context.vm.environments.push_private(environment);
+
+        context.vm.push(class_value);
+
+        Ok(CompletionType::Normal)
+    }
+}
+
+/// `PopPrivateEnvironment` implements the Opcode Operation for `Opcode::PopPrivateEnvironment`
+///
+/// Operation:
+///  - Pop a private environment.
+#[derive(Debug, Clone, Copy)]
+pub(crate) struct PopPrivateEnvironment;
+
+impl Operation for PopPrivateEnvironment {
+    const NAME: &'static str = "PopPrivateEnvironment";
+    const INSTRUCTION: &'static str = "INST - PopPrivateEnvironment";
+
+    fn execute(context: &mut Context<'_>) -> JsResult<CompletionType> {
+        context.vm.environments.pop_private();
+
+        Ok(CompletionType::Normal)
+    }
+}

boa_engine/src/vm/opcode/set/private.rs

@@ -23,6 +23,13 @@ impl Operation for SetPrivateField {
         let value = context.vm.pop();
         let object = context.vm.pop();
         let base_obj = object.to_object(context)?;
+
+        let name = context
+            .vm
+            .environments
+            .resolve_private_identifier(name.description())
+            .expect("private name must be in environment");
+
         base_obj.private_set(&name, value.clone(), context)?;
         context.vm.push(value);
         Ok(CompletionType::Normal)
@@ -48,9 +55,11 @@ impl Operation for DefinePrivateField {
         let object = object
             .as_object()
             .expect("class prototype must be an object");
-        object
-            .borrow_mut()
-            .append_private_element(name, PrivateElement::Field(value));
+
+        object.borrow_mut().append_private_element(
+            object.private_name(name.description()),
+            PrivateElement::Field(value),
+        );
 
         Ok(CompletionType::Normal)
     }
@@ -88,9 +97,11 @@ impl Operation for SetPrivateMethod {
         let object = object
             .as_object()
             .expect("class prototype must be an object");
-        object
-            .borrow_mut()
-            .append_private_element(name, PrivateElement::Method(value.clone()));
+
+        object.borrow_mut().append_private_element(
+            object.private_name(name.description()),
+            PrivateElement::Method(value.clone()),
+        );
         let mut value_mut = value.borrow_mut();
         let function = value_mut
             .as_function_mut()
@@ -123,7 +134,7 @@ impl Operation for SetPrivateSetter {
             .expect("class prototype must be an object");
 
         object.borrow_mut().append_private_element(
-            name,
+            object.private_name(name.description()),
             PrivateElement::Accessor {
                 getter: None,
                 setter: Some(value.clone()),
@@ -161,7 +172,7 @@ impl Operation for SetPrivateGetter {
             .expect("class prototype must be an object");
 
         object.borrow_mut().append_private_element(
-            name,
+            object.private_name(name.description()),
             PrivateElement::Accessor {
                 getter: Some(value.clone()),
                 setter: None,

boa_parser/src/parser/cursor/mod.rs

@@ -25,12 +25,6 @@ pub(super) enum SemicolonResult<'s> {
 pub(super) struct Cursor<R> {
     buffered_lexer: BufferedLexer<R>,
 
-    /// Tracks the number of nested private environments that the cursor is in.
-    private_environment_nested_index: usize,
-
-    /// Tracks the number of private environments on the root level of the code that is parsed.
-    private_environment_root_index: usize,
-
     /// Tracks if the cursor is in a arrow function declaration.
     arrow: bool,
 
@@ -53,8 +47,6 @@ where
     pub(super) fn new(reader: R) -> Self {
         Self {
             buffered_lexer: Lexer::new(reader).into(),
-            private_environment_nested_index: 0,
-            private_environment_root_index: 0,
             arrow: false,
             json_parse: false,
             identifier: 0,
@@ -150,34 +142,6 @@ where
         self.json_parse = json_parse;
     }
 
-    /// Push a new private environment.
-    #[inline]
-    pub(super) fn push_private_environment(&mut self) {
-        if !self.in_class() {
-            self.private_environment_root_index += 1;
-        }
-
-        self.private_environment_nested_index += 1;
-    }
-
-    /// Pop a private environment.
-    #[inline]
-    pub(super) fn pop_private_environment(&mut self) {
-        self.private_environment_nested_index -= 1;
-    }
-
-    /// Returns the current private environment root index.
-    #[inline]
-    pub(super) const fn private_environment_root_index(&self) -> usize {
-        self.private_environment_root_index
-    }
-
-    /// Returns if the cursor is in a class.
-    #[inline]
-    pub(super) const fn in_class(&self) -> bool {
-        self.private_environment_nested_index != 0
-    }
-
     /// Set the identifier of the cursor.
     #[inline]
     pub(super) fn set_identifier(&mut self, identifier: u32) {

boa_parser/src/parser/expression/left_hand_side/call.rs

@@ -112,12 +112,6 @@ where
                         }
                         TokenKind::NullLiteral => SimplePropertyAccess::new(lhs, Sym::NULL).into(),
                         TokenKind::PrivateIdentifier(name) => {
-                            if !cursor.in_class() {
-                                return Err(Error::general(
-                                    "Private identifier outside of class",
-                                    token.span().start(),
-                                ));
-                            }
                             PrivatePropertyAccess::new(lhs, PrivateName::new(*name)).into()
                         }
                         _ => {

boa_parser/src/parser/expression/left_hand_side/member.rs

@@ -201,12 +201,6 @@ where
                         }
                         TokenKind::NullLiteral => SimplePropertyAccess::new(lhs, Sym::NULL).into(),
                         TokenKind::PrivateIdentifier(name) => {
-                            if !cursor.in_class() {
-                                return Err(Error::general(
-                                    "Private identifier outside of class",
-                                    token.span().start(),
-                                ));
-                            }
                             PrivatePropertyAccess::new(lhs, PrivateName::new(*name)).into()
                         }
                         _ => {

boa_parser/src/parser/expression/left_hand_side/optional/mod.rs

@@ -60,8 +60,7 @@ where
     type Output = Optional;
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
-        fn parse_const_access<R: Read>(
-            cursor: &mut Cursor<R>,
+        fn parse_const_access(
             token: &Token,
             interner: &mut Interner,
         ) -> ParseResult<OptionalOperationKind> {
@@ -84,13 +83,6 @@ where
                     field: PropertyAccessField::Const(Sym::NULL),
                 },
                 TokenKind::PrivateIdentifier(name) => {
-                    if !cursor.in_class() {
-                        return Err(Error::general(
-                            "Private identifier outside of class",
-                            token.span().start(),
-                        ));
-                    }
-
                     OptionalOperationKind::PrivatePropertyAccess {
                         field: PrivateName::new(*name),
                     }
@@ -121,7 +113,7 @@ where
                     cursor.advance(interner);
                     let field = cursor.next(interner).or_abrupt()?;
 
-                    let item = parse_const_access(cursor, &field, interner)?;
+                    let item = parse_const_access(&field, interner)?;
 
                     items.push(OptionalOperation::new(item, false));
                     continue;
@@ -162,7 +154,7 @@ where
                 }
                 _ => {
                     let token = cursor.next(interner)?.expect("token disappeared");
-                    parse_const_access(cursor, &token, interner)?
+                    parse_const_access(&token, interner)?
                 }
             };
 

boa_parser/src/parser/expression/mod.rs

@@ -567,7 +567,6 @@ where
 
         if self.allow_in.0 {
             let token = cursor.peek(0, interner).or_abrupt()?;
-            let span = token.span();
             if let TokenKind::PrivateIdentifier(identifier) = token.kind() {
                 let identifier = *identifier;
                 let token = cursor.peek(1, interner).or_abrupt()?;
@@ -582,13 +581,6 @@ where
                         cursor.advance(interner);
                         cursor.advance(interner);
 
-                        if !cursor.in_class() {
-                            return Err(Error::general(
-                                "Private identifier outside of class",
-                                span.start(),
-                            ));
-                        }
-
                         let rhs =
                             ShiftExpression::new(self.name, self.allow_yield, self.allow_await)
                                 .parse(cursor, interner)?;

boa_parser/src/parser/mod.rs

@@ -22,9 +22,9 @@ use boa_ast::{
     expression::Identifier,
     function::FormalParameterList,
     operations::{
-        check_labels, contains, contains_invalid_object_literal, lexically_declared_names,
-        top_level_lexically_declared_names, top_level_var_declared_names, var_declared_names,
-        ContainsSymbol,
+        all_private_identifiers_valid, check_labels, contains, contains_invalid_object_literal,
+        lexically_declared_names, top_level_lexically_declared_names, top_level_var_declared_names,
+        var_declared_names, ContainsSymbol,
     },
     ModuleItemList, Position, StatementList,
 };
@@ -340,6 +340,16 @@ where
                     Position::new(1, 1),
                 ));
             }
+
+            // It is a Syntax Error if AllPrivateIdentifiersValid of StatementList with
+            // argument « » is false unless the source text containing ScriptBody is
+            // eval code that is being processed by a direct eval.
+            if !all_private_identifiers_valid(&body, Vec::new()) {
+                return Err(Error::general(
+                    "invalid private identifier usage",
+                    Position::new(1, 1),
+                ));
+            }
         }
 
         if let Err(error) = check_labels(&body) {

boa_parser/src/parser/statement/declaration/hoistable/class_decl/mod.rs

@@ -17,8 +17,7 @@ use crate::{
 use ast::{
     function::PrivateName,
     operations::{
-        check_labels, class_private_name_resolver, contains_invalid_object_literal,
-        lexically_declared_names, var_declared_names,
+        check_labels, contains_invalid_object_literal, lexically_declared_names, var_declared_names,
     },
 };
 use boa_ast::{
@@ -182,16 +181,12 @@ where
                 self.has_binding_identifier,
             ))
         } else {
-            cursor.push_private_environment();
-
             let body_start = cursor.peek(0, interner).or_abrupt()?.span().start();
             let (constructor, elements) =
                 ClassBody::new(self.name, self.allow_yield, self.allow_await)
                     .parse(cursor, interner)?;
             cursor.expect(Punctuator::CloseBlock, "class tail", interner)?;
 
-            cursor.pop_private_environment();
-
             if super_ref.is_none() {
                 if let Some(constructor) = &constructor {
                     if contains(constructor, ContainsSymbol::SuperCall) {
@@ -203,24 +198,13 @@ where
                 }
             }
 
-            let mut class = Class::new(
+            Ok(Class::new(
                 self.name,
                 super_ref,
                 constructor,
                 elements.into(),
                 self.has_binding_identifier,
-            );
-
-            if !cursor.in_class()
-                && !class_private_name_resolver(&mut class, cursor.private_environment_root_index())
-            {
-                return Err(Error::lex(LexError::Syntax(
-                    "invalid private name usage".into(),
-                    body_start,
-                )));
-            }
-
-            Ok(class)
+            ))
         }
     }
 }

boa_parser/src/parser/statement/mod.rs

@@ -47,7 +47,7 @@ use crate::{
     Error,
 };
 use ast::{
-    operations::{check_labels, contains_invalid_object_literal},
+    operations::{all_private_identifiers_valid, check_labels, contains_invalid_object_literal},
     Position,
 };
 use boa_ast::{
@@ -929,7 +929,17 @@ where
             list.push(item);
         }
 
-        Ok(list.into())
+        let list = list.into();
+
+        // It is a Syntax Error if AllPrivateIdentifiersValid of ModuleItemList with argument « » is false.
+        if !all_private_identifiers_valid(&list, Vec::new()) {
+            return Err(Error::general(
+                "invalid private identifier usage",
+                Position::new(1, 1),
+            ));
+        }
+
+        Ok(list)
     }
 }