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//! # Declarative Records
//!
//! Each declarative Environment Record is associated with an ECMAScript program scope containing variable,
//! `constant`, `let`, `class`, `module`, `import`, and/or function declarations.
//! A declarative Environment Record binds the set of identifiers defined by the declarations contained within its scope.
//! More info: [ECMA-262 sec-declarative-environment-records](https://tc39.es/ecma262/#sec-declarative-environment-records)
use crate::{
environment::{
environment_record_trait::EnvironmentRecordTrait,
lexical_environment::{Environment, EnvironmentType},
},
gc::{Finalize, Trace},
object::JsObject,
BoaProfiler, Context, JsResult, JsValue,
};
use gc::{Gc, GcCell};
use rustc_hash::FxHashMap;
/// Declarative Bindings have a few properties for book keeping purposes, such as mutability (const vs let).
/// Can it be deleted? and strict mode.
///
/// So we need to create a struct to hold these values.
/// From this point onwards, a binding is referring to one of these structures.
#[derive(Trace, Finalize, Debug, Clone)]
pub struct DeclarativeEnvironmentRecordBinding {
pub value: Option<JsValue>,
pub can_delete: bool,
pub mutable: bool,
pub strict: bool,
}
/// A declarative Environment Record binds the set of identifiers defined by the
/// declarations contained within its scope.
#[derive(Debug, Trace, Finalize, Clone)]
pub struct DeclarativeEnvironmentRecord {
pub env_rec: GcCell<FxHashMap<Box<str>, DeclarativeEnvironmentRecordBinding>>,
pub outer_env: Option<Environment>,
}
impl DeclarativeEnvironmentRecord {
pub fn new(env: Option<Environment>) -> DeclarativeEnvironmentRecord {
let _timer = BoaProfiler::global().start_event("new_declarative_environment", "env");
DeclarativeEnvironmentRecord {
env_rec: GcCell::new(FxHashMap::default()),
outer_env: env,
}
}
}
impl EnvironmentRecordTrait for DeclarativeEnvironmentRecord {
/// `9.1.1.1.1 HasBinding ( N )`
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-declarative-environment-records-hasbinding-n
fn has_binding(&self, name: &str, _context: &mut Context) -> JsResult<bool> {
// 1. If envRec has a binding for the name that is the value of N, return true.
// 2. Return false.
Ok(self.env_rec.borrow().contains_key(name))
}
/// `9.1.1.1.2 CreateMutableBinding ( N, D )`
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-declarative-environment-records-createmutablebinding-n-d
fn create_mutable_binding(
&self,
name: &str,
deletion: bool,
allow_name_reuse: bool,
_context: &mut Context,
) -> JsResult<()> {
// 1. Assert: envRec does not already have a binding for N.
if !allow_name_reuse {
assert!(
!self.env_rec.borrow().contains_key(name),
"Identifier {} has already been declared",
name
);
}
// 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.
self.env_rec.borrow_mut().insert(
name.into(),
DeclarativeEnvironmentRecordBinding {
value: None,
can_delete: deletion,
mutable: true,
strict: false,
},
);
// 3. Return NormalCompletion(empty).
Ok(())
}
/// `9.1.1.1.3 CreateImmutableBinding ( N, S )`
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-declarative-environment-records-createimmutablebinding-n-s
fn create_immutable_binding(
&self,
name: &str,
strict: bool,
_context: &mut Context,
) -> JsResult<()> {
// 1. Assert: envRec does not already have a binding for N.
assert!(
!self.env_rec.borrow().contains_key(name),
"Identifier {} has already been declared",
name
);
// 2. Create an immutable binding in envRec for N and record that it is uninitialized.
// If S is true, record that the newly created binding is a strict binding.
self.env_rec.borrow_mut().insert(
name.into(),
DeclarativeEnvironmentRecordBinding {
value: None,
can_delete: true,
mutable: false,
strict,
},
);
// 3. Return NormalCompletion(empty).
Ok(())
}
/// `9.1.1.1.4 InitializeBinding ( N, V )`
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-declarative-environment-records-initializebinding-n-v
fn initialize_binding(
&self,
name: &str,
value: JsValue,
_context: &mut Context,
) -> JsResult<()> {
if let Some(ref mut record) = self.env_rec.borrow_mut().get_mut(name) {
if record.value.is_none() {
// 2. Set the bound value for N in envRec to V.
// 3. Record that the binding for N in envRec has been initialized.
record.value = Some(value);
// 4. Return NormalCompletion(empty).
return Ok(());
}
}
// 1. Assert: envRec must have an uninitialized binding for N.
panic!("record must have binding for {}", name);
}
/// `9.1.1.1.5 SetMutableBinding ( N, V, S )`
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-declarative-environment-records-setmutablebinding-n-v-s
#[allow(clippy::else_if_without_else)]
fn set_mutable_binding(
&self,
name: &str,
value: JsValue,
mut strict: bool,
context: &mut Context,
) -> JsResult<()> {
// 1. If envRec does not have a binding for N, then
if self.env_rec.borrow().get(name).is_none() {
// a. If S is true, throw a ReferenceError exception.
if strict {
return Err(context.construct_reference_error(format!("{} not found", name)));
}
// b. Perform envRec.CreateMutableBinding(N, true).
self.create_mutable_binding(name, true, false, context)?;
// c. Perform envRec.InitializeBinding(N, V).
self.initialize_binding(name, value, context)?;
// d. Return NormalCompletion(empty).
return Ok(());
}
let (binding_strict, binding_value_is_none, binding_mutable) = {
let env_rec = self.env_rec.borrow();
let binding = env_rec.get(name).unwrap();
(binding.strict, binding.value.is_none(), binding.mutable)
};
// 2. If the binding for N in envRec is a strict binding, set S to true.
if binding_strict {
strict = true;
}
// 3. If the binding for N in envRec has not yet been initialized, throw a ReferenceError exception.
if binding_value_is_none {
return Err(
context.construct_reference_error(format!("{} has not been initialized", name))
);
// 4. Else if the binding for N in envRec is a mutable binding, change its bound value to V.
} else if binding_mutable {
let mut env_rec = self.env_rec.borrow_mut();
let binding = env_rec.get_mut(name).unwrap();
binding.value = Some(value);
// 5. Else,
// a. Assert: This is an attempt to change the value of an immutable binding.
// b. If S is true, throw a TypeError exception.
} else if strict {
return Err(context
.construct_type_error(format!("Cannot mutate an immutable binding {}", name)));
}
// 6. Return NormalCompletion(empty).
Ok(())
}
/// `9.1.1.1.6 GetBindingValue ( N, S )`
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-declarative-environment-records-getbindingvalue-n-s
fn get_binding_value(
&self,
name: &str,
_strict: bool,
context: &mut Context,
) -> JsResult<JsValue> {
// 1. Assert: envRec has a binding for N.
// 2. If the binding for N in envRec is an uninitialized binding, throw a ReferenceError exception.
// 3. Return the value currently bound to N in envRec.
if let Some(binding) = self.env_rec.borrow().get(name) {
if let Some(ref val) = binding.value {
Ok(val.clone())
} else {
context.throw_reference_error(format!("{} is an uninitialized binding", name))
}
} else {
panic!("Cannot get binding value for {}", name);
}
}
/// `9.1.1.1.7 DeleteBinding ( N )`
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-declarative-environment-records-deletebinding-n
fn delete_binding(&self, name: &str, _context: &mut Context) -> JsResult<bool> {
// 1. Assert: envRec has a binding for the name that is the value of N.
// 2. If the binding for N in envRec cannot be deleted, return false.
// 3. Remove the binding for N from envRec.
// 4. Return true.
match self.env_rec.borrow().get(name) {
Some(binding) => {
if binding.can_delete {
self.env_rec.borrow_mut().remove(name);
Ok(true)
} else {
Ok(false)
}
}
None => panic!("env_rec has no binding for {}", name),
}
}
/// `9.1.1.1.8 HasThisBinding ( )`
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-declarative-environment-records-hasthisbinding
fn has_this_binding(&self) -> bool {
// 1. Return false.
false
}
fn get_this_binding(&self, _context: &mut Context) -> JsResult<JsValue> {
Ok(JsValue::undefined())
}
/// `9.1.1.1.9 HasSuperBinding ( )`
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-declarative-environment-records-hassuperbinding
fn has_super_binding(&self) -> bool {
// 1. Return false.
false
}
/// `9.1.1.1.10 WithBaseObject ( )`
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-declarative-environment-records-withbaseobject
fn with_base_object(&self) -> Option<JsObject> {
None
}
fn get_outer_environment_ref(&self) -> Option<&Environment> {
self.outer_env.as_ref()
}
fn set_outer_environment(&mut self, env: Environment) {
self.outer_env = Some(env);
}
fn get_environment_type(&self) -> EnvironmentType {
EnvironmentType::Declarative
}
}
impl From<DeclarativeEnvironmentRecord> for Environment {
fn from(env: DeclarativeEnvironmentRecord) -> Environment {
Gc::new(Box::new(env))
}
}