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feat(erm): implement block-scoped disposal semantics for using declarations #5252

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feat(erm): implement block-scoped disposal semantics for using declarations #5252

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21 changes: 19 additions & 2 deletions core/ast/src/scope.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -103,9 +103,10 @@ pub(crate) struct Inner {
index: Cell<u32>,
bindings: RefCell<Vec<Binding>>,
function: bool,
// Has the `this` been accessed/escaped outside the function environment boundary.
this_escaped: Cell<bool>,

has_using_declarations: Cell<bool>,

context: Rc<ScopeContext>,
}

Expand All @@ -121,6 +122,7 @@ impl Scope {
bindings: RefCell::default(),
function: true,
this_escaped: Cell::new(false),
has_using_declarations: Cell::new(false),
context: Rc::default(),
}),
}
Expand All @@ -136,6 +138,7 @@ impl Scope {
bindings: RefCell::default(),
function,
this_escaped: Cell::new(false),
has_using_declarations: Cell::new(false),
context: parent.inner.context.clone(),
outer: Some(parent),
}),
Expand All @@ -145,14 +148,28 @@ impl Scope {
/// Checks if the scope has only local bindings.
#[must_use]
pub fn all_bindings_local(&self) -> bool {
// if self.inner.function && self.inn
if self.inner.has_using_declarations.get() {
return false;
}

self.inner
.bindings
.borrow()
.iter()
.all(|binding| !binding.escapes())
}

/// Mark the scope as having using declarations, to prevent `PushScope` optimization
pub fn set_has_using_declarations(&self) {
self.inner.has_using_declarations.set(true);
}

/// Returns true if using declarations exist in this scope
#[must_use]
pub fn has_using_declarations(&self) -> bool {
self.inner.has_using_declarations.get()
}

/// Marks all bindings in this scope as escaping.
pub fn escape_all_bindings(&self) {
for binding in self.inner.bindings.borrow_mut().iter_mut() {
Expand Down
68 changes: 58 additions & 10 deletions core/ast/src/scope_analyzer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -974,6 +974,14 @@ impl<'ast> VisitorMut<'ast> for BindingCollectorVisitor<'_> {
let scope = match &mut node.inner.init {
Some(ForLoopInitializer::Lexical(decl)) => {
let mut scope = Scope::new(self.scope.clone(), false);

if matches!(
decl.declaration,
LexicalDeclaration::Using(_) | LexicalDeclaration::AwaitUsing(_)
) {
scope.set_has_using_declarations();
}

let names = bound_names(&decl.declaration);
if decl.declaration.is_const() {
for name in &names {
Expand Down Expand Up @@ -1800,6 +1808,16 @@ fn global_declaration_instantiation(
env.create_immutable_binding(name, true);
}
}
Declaration::Lexical(
LexicalDeclaration::Using(declaration)
| LexicalDeclaration::AwaitUsing(declaration),
) => {
env.set_has_using_declarations();
for name in bound_names(declaration) {
let name = name.to_js_string(interner);
env.create_immutable_binding(name.clone(), true);
}
}
_ => {}
}
}
Expand Down Expand Up @@ -1832,6 +1850,18 @@ where

// 3. For each element d of declarations, do
for d in &declarations {
// Mark scope as containing `using` declarations so the bytecompiler
// does NOT optimize away PushScope/PopEnvironment — we need those
// opcodes to trigger block-scoped resource disposal.
if matches!(
d,
LexicallyScopedDeclaration::LexicalDeclaration(
LexicalDeclaration::Using(_) | LexicalDeclaration::AwaitUsing(_)
)
) {
scope.set_has_using_declarations();
}

// i. If IsConstantDeclaration of d is true, then
if let LexicallyScopedDeclaration::LexicalDeclaration(LexicalDeclaration::Const(d)) = d {
// a. For each element dn of the BoundNames of d, do
Expand Down Expand Up @@ -1861,7 +1891,7 @@ where
}
}

if scope.num_bindings() > 0 {
if scope.num_bindings() > 0 || scope.has_using_declarations() {
Some(scope)
} else {
None
Expand Down Expand Up @@ -2180,6 +2210,16 @@ fn function_declaration_instantiation(
lex_env.create_immutable_binding(name, true);
}
}
Declaration::Lexical(
LexicalDeclaration::Using(declaration)
| LexicalDeclaration::AwaitUsing(declaration),
) => {
lex_env.set_has_using_declarations();
for name in bound_names(declaration) {
let name = name.to_js_string(interner);
lex_env.create_immutable_binding(name.clone(), true);
}
}
_ => {}
}
}
Expand Down Expand Up @@ -2255,16 +2295,14 @@ fn module_instantiation(module: &Module, env: &Scope, interner: &Interner) {
drop(env.create_mutable_binding(name, false));
}
}
LexicallyScopedDeclaration::LexicalDeclaration(LexicalDeclaration::Using(u)) => {
for name in bound_names(u) {
let name = name.to_js_string(interner);
drop(env.create_mutable_binding(name, false));
}
}
LexicallyScopedDeclaration::LexicalDeclaration(LexicalDeclaration::AwaitUsing(au)) => {
for name in bound_names(au) {
LexicallyScopedDeclaration::LexicalDeclaration(
LexicalDeclaration::Using(declaration)
| LexicalDeclaration::AwaitUsing(declaration),
) => {
env.set_has_using_declarations();
for name in bound_names(declaration) {
let name = name.to_js_string(interner);
drop(env.create_mutable_binding(name, false));
env.create_immutable_binding(name.clone(), true);
}
}
LexicallyScopedDeclaration::AssignmentExpression(expr) => {
Expand Down Expand Up @@ -2498,6 +2536,16 @@ pub(crate) fn eval_declaration_instantiation_scope(
lex_env.create_immutable_binding(name, true);
}
}
Declaration::Lexical(
LexicalDeclaration::Using(declaration)
| LexicalDeclaration::AwaitUsing(declaration),
) => {
lex_env.set_has_using_declarations();
for name in bound_names(declaration) {
let name = name.to_js_string(interner);
lex_env.create_immutable_binding(name, true);
}
}
_ => {}
}
}
Expand Down
14 changes: 6 additions & 8 deletions core/engine/src/bytecompiler/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2259,9 +2259,7 @@ impl<'ctx> ByteCompiler<'ctx> {
self.bytecode.emit_store_undefined(value.variable());
}

// TODO(@abhinavs1920): Add resource to disposal stack
// For now, we just bind the variable like a let declaration
// Full implementation will add: AddDisposableResource opcode
self.bytecode.emit_add_disposable_resource(value.variable());

self.emit_binding(BindingOpcode::InitLexical, ident, &value);
self.register_allocator.dealloc(value);
Expand All @@ -2275,7 +2273,7 @@ impl<'ctx> ByteCompiler<'ctx> {
self.bytecode.emit_store_undefined(value.variable());
}

// TODO: Same as above
self.bytecode.emit_add_disposable_resource(value.variable());

self.compile_declaration_pattern(
pattern,
Expand All @@ -2300,9 +2298,8 @@ impl<'ctx> ByteCompiler<'ctx> {
self.bytecode.emit_store_undefined(value.variable());
}

// TODO: Add resource to async disposal stack
// For now, we just bind the variable like a let declaration
// Full implementation will add: AddAsyncDisposableResource opcode
self.bytecode
.emit_add_async_disposable_resource(value.variable());

self.emit_binding(BindingOpcode::InitLexical, ident, &value);
self.register_allocator.dealloc(value);
Expand All @@ -2316,7 +2313,8 @@ impl<'ctx> ByteCompiler<'ctx> {
self.bytecode.emit_store_undefined(value.variable());
}

// TODO: SAME
self.bytecode
.emit_add_async_disposable_resource(value.variable());
self.compile_declaration_pattern(
pattern,
BindingOpcode::InitLexical,
Expand Down
1 change: 1 addition & 0 deletions core/engine/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -105,6 +105,7 @@ pub mod value;
pub mod vm;

mod host_defined;
mod resource_management;
mod sys;

mod spanned_source_text;
Expand Down
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