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Fix destructive for-of loop assignments (#2803)
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This Pull Request changes the following:

- Fix the assignment of variables in destructive for-of initializers.
- Fix the environment handling in the compilation of `for-of/in` loops.
- Close iterators in destructive for-of loop assignments, when the code throws during the assignment.
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@raskad
raskad committed Apr 11, 2023
1 parent 2f580bb commit ff0a37f
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Showing 8 changed files with 254 additions and 53 deletions.
56 changes: 40 additions & 16 deletions boa_engine/src/bytecompiler/declaration/declaration_pattern.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -176,6 +176,7 @@ impl ByteCompiler<'_, '_> {
Pattern::Array(pattern) => {
self.emit_opcode(Opcode::ValueNotNullOrUndefined);
self.emit_opcode(Opcode::GetIterator);
self.emit_opcode(Opcode::IteratorClosePush);
match pattern.bindings().split_last() {
None => self.emit_opcode(Opcode::PushFalse),
Some((last, rest)) => {
Expand All @@ -185,6 +186,7 @@ impl ByteCompiler<'_, '_> {
self.compile_array_pattern_element(last, def, true);
}
}
self.emit_opcode(Opcode::IteratorClosePop);
self.iterator_close(false);
}
}
Expand All @@ -209,7 +211,7 @@ impl ByteCompiler<'_, '_> {
match element {
// ArrayBindingPattern : [ Elision ]
Elision => {
self.emit_opcode(Opcode::IteratorNext);
self.emit_opcode(Opcode::IteratorNextSetDone);
if with_done {
self.emit_opcode(Opcode::IteratorUnwrapNext);
}
Expand All @@ -220,7 +222,7 @@ impl ByteCompiler<'_, '_> {
ident,
default_init,
} => {
self.emit_opcode(Opcode::IteratorNext);
self.emit_opcode(Opcode::IteratorNextSetDone);
self.emit_opcode(unwrapping);
if let Some(init) = default_init {
let skip = self.emit_opcode_with_operand(Opcode::JumpIfNotUndefined);
Expand All @@ -230,20 +232,31 @@ impl ByteCompiler<'_, '_> {
self.emit_binding(def, *ident);
}
PropertyAccess { access } => {
self.emit_opcode(Opcode::IteratorNext);
self.emit_opcode(unwrapping);
self.access_set(
Access::Property { access },
false,
ByteCompiler::access_set_top_of_stack_expr_fn,
);
self.access_set(Access::Property { access }, false, |compiler, level| {
if level != 0 {
compiler.emit_opcode(Opcode::RotateLeft);
compiler.emit_u8(level + 2);
compiler.emit_opcode(Opcode::RotateLeft);
compiler.emit_u8(level + 2);
}
compiler.emit_opcode(Opcode::IteratorNextSetDone);
compiler.emit_opcode(unwrapping);
if level != 0 {
compiler.emit_opcode(Opcode::RotateLeft);
compiler.emit_u8(level + 3 + u8::from(with_done));
compiler.emit_opcode(Opcode::RotateLeft);
compiler.emit_u8(level + 3 + u8::from(with_done));
compiler.emit_opcode(Opcode::RotateLeft);
compiler.emit_u8(level + 1);
}
});
}
// BindingElement : BindingPattern Initializer[opt]
Pattern {
pattern,
default_init,
} => {
self.emit_opcode(Opcode::IteratorNext);
self.emit_opcode(Opcode::IteratorNextSetDone);
self.emit_opcode(unwrapping);

if let Some(init) = default_init {
Expand All @@ -263,12 +276,23 @@ impl ByteCompiler<'_, '_> {
}
}
PropertyAccessRest { access } => {
self.emit_opcode(Opcode::IteratorToArray);
self.access_set(
Access::Property { access },
false,
ByteCompiler::access_set_top_of_stack_expr_fn,
);
self.access_set(Access::Property { access }, false, |compiler, level| {
if level != 0 {
compiler.emit_opcode(Opcode::RotateLeft);
compiler.emit_u8(level + 2);
compiler.emit_opcode(Opcode::RotateLeft);
compiler.emit_u8(level + 2);
}
compiler.emit_opcode(Opcode::IteratorToArray);
if level != 0 {
compiler.emit_opcode(Opcode::RotateLeft);
compiler.emit_u8(level + 3);
compiler.emit_opcode(Opcode::RotateLeft);
compiler.emit_u8(level + 3);
compiler.emit_opcode(Opcode::RotateLeft);
compiler.emit_u8(level + 1);
}
});
if with_done {
self.emit_opcode(Opcode::PushTrue);
}
Expand Down
77 changes: 47 additions & 30 deletions boa_engine/src/bytecompiler/statement/loop.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -89,15 +89,19 @@ impl ByteCompiler<'_, '_> {
label: Option<Sym>,
configurable_globals: bool,
) {
let init_bound_names = bound_names(for_in_loop.initializer());
if init_bound_names.is_empty() {
let initializer_bound_names = match for_in_loop.initializer() {
IterableLoopInitializer::Let(declaration)
| IterableLoopInitializer::Const(declaration) => bound_names(declaration),
_ => Vec::new(),
};
if initializer_bound_names.is_empty() {
self.compile_expr(for_in_loop.target(), true);
} else {
self.push_compile_environment(false);
let push_env = self.emit_opcode_with_two_operands(Opcode::PushDeclarativeEnvironment);

for name in init_bound_names {
self.create_mutable_binding(name, false, false);
for name in &initializer_bound_names {
self.create_mutable_binding(*name, false, false);
}
self.compile_expr(for_in_loop.target(), true);

Expand All @@ -119,12 +123,17 @@ impl ByteCompiler<'_, '_> {
self.patch_jump_with_target(continue_label, start_address);
self.patch_jump_with_target(loop_start, start_address);

self.push_compile_environment(false);
let push_env = self.emit_opcode_with_two_operands(Opcode::PushDeclarativeEnvironment);
self.emit_opcode(Opcode::Pop); // pop the `done` value.
self.emit_opcode(Opcode::IteratorNext);
let exit = self.emit_opcode_with_operand(Opcode::IteratorUnwrapNextOrJump);

let iteration_environment = if initializer_bound_names.is_empty() {
None
} else {
self.push_compile_environment(false);
Some(self.emit_opcode_with_two_operands(Opcode::PushDeclarativeEnvironment))
};

match for_in_loop.initializer() {
IterableLoopInitializer::Identifier(ident) => {
self.create_mutable_binding(*ident, true, true);
Expand Down Expand Up @@ -176,19 +185,18 @@ impl ByteCompiler<'_, '_> {
}
},
IterableLoopInitializer::Pattern(pattern) => {
for ident in bound_names(pattern) {
self.create_mutable_binding(ident, true, true);
}
self.compile_declaration_pattern(pattern, BindingOpcode::InitVar);
self.compile_declaration_pattern(pattern, BindingOpcode::SetName);
}
}

self.compile_stmt(for_in_loop.body(), false, configurable_globals);

let env_info = self.pop_compile_environment();
self.patch_jump_with_target(push_env.0, env_info.num_bindings as u32);
self.patch_jump_with_target(push_env.1, env_info.index as u32);
self.emit_opcode(Opcode::PopEnvironment);
if let Some(iteration_environment) = iteration_environment {
let env_info = self.pop_compile_environment();
self.patch_jump_with_target(iteration_environment.0, env_info.num_bindings as u32);
self.patch_jump_with_target(iteration_environment.1, env_info.index as u32);
self.emit_opcode(Opcode::PopEnvironment);
}

self.emit(Opcode::Jump, &[start_address]);

Expand All @@ -197,7 +205,9 @@ impl ByteCompiler<'_, '_> {
self.patch_jump(cont_exit_label);
self.pop_loop_control_info();
self.emit_opcode(Opcode::LoopEnd);
self.iterator_close(false);
self.emit_opcode(Opcode::Pop);
self.emit_opcode(Opcode::Pop);
self.emit_opcode(Opcode::Pop);

self.patch_jump(early_exit);
}
Expand All @@ -208,15 +218,19 @@ impl ByteCompiler<'_, '_> {
label: Option<Sym>,
configurable_globals: bool,
) {
let init_bound_names = bound_names(for_of_loop.initializer());
if init_bound_names.is_empty() {
let initializer_bound_names = match for_of_loop.initializer() {
IterableLoopInitializer::Let(declaration)
| IterableLoopInitializer::Const(declaration) => bound_names(declaration),
_ => Vec::new(),
};
if initializer_bound_names.is_empty() {
self.compile_expr(for_of_loop.iterable(), true);
} else {
self.push_compile_environment(false);
let push_env = self.emit_opcode_with_two_operands(Opcode::PushDeclarativeEnvironment);

for name in init_bound_names {
self.create_mutable_binding(name, false, false);
for name in &initializer_bound_names {
self.create_mutable_binding(*name, false, false);
}
self.compile_expr(for_of_loop.iterable(), true);

Expand All @@ -241,9 +255,6 @@ impl ByteCompiler<'_, '_> {
self.patch_jump_with_target(loop_start, start_address);
self.patch_jump_with_target(cont_label, start_address);

self.push_compile_environment(false);
let push_env = self.emit_opcode_with_two_operands(Opcode::PushDeclarativeEnvironment);

self.emit_opcode(Opcode::Pop); // pop the `done` value.
self.emit_opcode(Opcode::IteratorNext);
if for_of_loop.r#await() {
Expand All @@ -252,6 +263,13 @@ impl ByteCompiler<'_, '_> {
}
let exit = self.emit_opcode_with_operand(Opcode::IteratorUnwrapNextOrJump);

let iteration_environment = if initializer_bound_names.is_empty() {
None
} else {
self.push_compile_environment(false);
Some(self.emit_opcode_with_two_operands(Opcode::PushDeclarativeEnvironment))
};

match for_of_loop.initializer() {
IterableLoopInitializer::Identifier(ref ident) => {
self.create_mutable_binding(*ident, true, true);
Expand Down Expand Up @@ -303,19 +321,18 @@ impl ByteCompiler<'_, '_> {
}
},
IterableLoopInitializer::Pattern(pattern) => {
for ident in bound_names(pattern) {
self.create_mutable_binding(ident, true, true);
}
self.compile_declaration_pattern(pattern, BindingOpcode::InitVar);
self.compile_declaration_pattern(pattern, BindingOpcode::SetName);
}
}

self.compile_stmt(for_of_loop.body(), false, configurable_globals);

let env_info = self.pop_compile_environment();
self.patch_jump_with_target(push_env.0, env_info.num_bindings as u32);
self.patch_jump_with_target(push_env.1, env_info.index as u32);
self.emit_opcode(Opcode::PopEnvironment);
if let Some(iteration_environment) = iteration_environment {
let env_info = self.pop_compile_environment();
self.patch_jump_with_target(iteration_environment.0, env_info.num_bindings as u32);
self.patch_jump_with_target(iteration_environment.1, env_info.index as u32);
self.emit_opcode(Opcode::PopEnvironment);
}

self.emit(Opcode::Jump, &[start_address]);

Expand Down
12 changes: 9 additions & 3 deletions boa_engine/src/vm/call_frame/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2,14 +2,16 @@
//!
//! This module will provides everything needed to implement the `CallFrame`

use crate::{object::JsObject, vm::CodeBlock};
use boa_gc::{Finalize, Gc, Trace};

mod abrupt_record;
mod env_stack;

use crate::{object::JsObject, vm::CodeBlock};
use boa_gc::{Finalize, Gc, Trace};
use thin_vec::ThinVec;

pub(crate) use abrupt_record::AbruptCompletionRecord;
pub(crate) use env_stack::EnvStackEntry;

/// A `CallFrame` holds the state of a function call.
#[derive(Clone, Debug, Finalize, Trace)]
pub struct CallFrame {
Expand All @@ -33,6 +35,9 @@ pub struct CallFrame {
// When an async generator is resumed, the generator object is needed
// to fulfill the steps 4.e-j in [AsyncGeneratorStart](https://tc39.es/ecma262/#sec-asyncgeneratorstart).
pub(crate) async_generator: Option<JsObject>,

// Iterators and their `[[Done]]` flags that must be closed when an abrupt completion is thrown.
pub(crate) iterators: ThinVec<(JsObject, bool)>,
}

/// ---- `CallFrame` creation methods ----
Expand All @@ -52,6 +57,7 @@ impl CallFrame {
arg_count: 0,
generator_resume_kind: GeneratorResumeKind::Normal,
async_generator: None,
iterators: ThinVec::new(),
}
}

Expand Down
3 changes: 3 additions & 0 deletions boa_engine/src/vm/code_block.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -448,9 +448,12 @@ impl CodeBlock {
| Opcode::GetIterator
| Opcode::GetAsyncIterator
| Opcode::IteratorNext
| Opcode::IteratorNextSetDone
| Opcode::IteratorUnwrapNext
| Opcode::IteratorUnwrapValue
| Opcode::IteratorToArray
| Opcode::IteratorClosePush
| Opcode::IteratorClosePop
| Opcode::RequireObjectCoercible
| Opcode::ValueNotNullOrUndefined
| Opcode::RestParameterInit
Expand Down
3 changes: 3 additions & 0 deletions boa_engine/src/vm/flowgraph/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -502,9 +502,12 @@ impl CodeBlock {
| Opcode::GetIterator
| Opcode::GetAsyncIterator
| Opcode::IteratorNext
| Opcode::IteratorNextSetDone
| Opcode::IteratorUnwrapNext
| Opcode::IteratorUnwrapValue
| Opcode::IteratorToArray
| Opcode::IteratorClosePush
| Opcode::IteratorClosePop
| Opcode::RequireObjectCoercible
| Opcode::ValueNotNullOrUndefined
| Opcode::RestParameterInit
Expand Down
16 changes: 16 additions & 0 deletions boa_engine/src/vm/opcode/control_flow/throw.rs
View file
Original file line number Diff line number Diff line change
@@ -1,7 +1,9 @@
use crate::{
js_string,
vm::{call_frame::AbruptCompletionRecord, opcode::Operation, CompletionType},
Context, JsError, JsNativeError, JsResult,
};
use thin_vec::ThinVec;

/// `Throw` implements the Opcode Operation for `Opcode::Throw`
///
Expand All @@ -20,6 +22,20 @@ impl Operation for Throw {
} else {
JsError::from_opaque(context.vm.pop())
};

// Close all iterators that are still open.
let mut iterators = ThinVec::new();
std::mem::swap(&mut iterators, &mut context.vm.frame_mut().iterators);
for (iterator, done) in iterators {
if done {
continue;
}
if let Ok(Some(f)) = iterator.get_method(js_string!("return"), context) {
drop(f.call(&iterator.into(), &[], context));
}
}
context.vm.err.take();

// 1. Find the viable catch and finally blocks
let current_address = context.vm.frame().pc;
let viable_catch_candidates = context
Expand Down
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