Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

16 files changed, 5233 insertions, 0 deletions

diff --git a/third_party/rust/jsparagus-emitter/.cargo-checksum.json b/third_party/rust/jsparagus-emitter/.cargo-checksum.json
new file mode 100644
index 0000000000..5a4fce48c8
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/.cargo-checksum.json
@@ -0,0 +1 @@
+{"files":{"Cargo.toml":"97ba372ad5ce5a4a16e8e2d0fd086b66e3383d6577b5c68de289e8767085b0a8","src/array_emitter.rs":"bbc6528321f1d11d7c86c4f2bfdcfc9dced8f0b8b1c30c9f0a5355f300d196b6","src/ast_emitter.rs":"050858e25f6bab6787771058afe504c66e74e9026e9ce873160bccc6366eca47","src/block_emitter.rs":"78965260d87a66c5324d6f3bdfea0f1938f8037f70adde148dbb2db599d1b2c0","src/compilation_info.rs":"b0d91b0f8d6940cb7087b474c3c814b758c8ce8d9027c415b76ad4af78be6140","src/control_structures.rs":"b32fbfff53bd378dcb45d63620006bea15c2fec1e7bc0bb163567dfe086e4931","src/dis.rs":"4a335d813fa965482ca0f20a7b9295a55ce7625b577d42bd8b33b156b81c6306","src/emitter.rs":"41a6a642d1970e625c264fc58bf245c6975b1e2d86707481ce4f942798c4b48a","src/emitter_scope.rs":"93c2b2a324ccb46b74adb2a28f56360a32652088e59c03641b4f1b608549dc78","src/expression_emitter.rs":"f8e02785dffb179bbe9fe58e45bbfccc08adc3ad0a071a0073bed0feedc8ed9a","src/function_declaration_emitter.rs":"0e6ae706ced215882f3a45b6e13f022ec1effa8edf1026b7ba7988810646982b","src/lib.rs":"f91576fb0f1e3cf444dd1d8ee25ee9bfd0b1e890e427a3863fdb6a4ad1611b61","src/object_emitter.rs":"998423b3d6ef8797fadef6763803627df72fde292b1b34d6a41b2e66a331a181","src/reference_op_emitter.rs":"e1507033c17318f59dbbdd1514d1bd1263f0c7d72530d0f2b2ab071d58b39f72","src/script_emitter.rs":"150a3d6330f40099ad1df8c52cd1831e3ef0fd4eecf44a20e3fff7acef2dd640"},"package":null}
\ No newline at end of file
diff --git a/third_party/rust/jsparagus-emitter/Cargo.toml b/third_party/rust/jsparagus-emitter/Cargo.toml
new file mode 100644
index 0000000000..0bc772dac6
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/Cargo.toml
@@ -0,0 +1,34 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+name = "jsparagus-emitter"
+version = "0.1.0"
+authors = ["khyperia <github@khyperia.com>"]
+license = "MIT/Apache-2.0"
+
+[dependencies]
+bumpalo = "3.4.0"
+byteorder = "1.3.2"
+indexmap = "2.0"
+
+[dependencies.jsparagus-ast]
+path = "../ast"
+
+[dependencies.jsparagus-scope]
+path = "../scope"
+
+[dependencies.jsparagus-stencil]
+path = "../stencil"
+
+[dev-dependencies.jsparagus-parser]
+path = "../parser"
diff --git a/third_party/rust/jsparagus-emitter/src/array_emitter.rs b/third_party/rust/jsparagus-emitter/src/array_emitter.rs
new file mode 100644
index 0000000000..b44137182e
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/array_emitter.rs
@@ -0,0 +1,176 @@
+use crate::ast_emitter::AstEmitter;
+use crate::emitter::EmitError;
+
+/// Struct for emitting bytecode for an array element.
+pub struct ArrayElementEmitter<'a, F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub state: &'a mut ArrayEmitterState,
+    pub elem: F,
+}
+
+impl<'a, F> ArrayElementEmitter<'a, F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack] ARRAY INDEX?
+
+        (self.elem)(emitter)?;
+        //              [stack] ARRAY INDEX? ELEM
+
+        match &mut self.state.0 {
+            ArrayEmitterStateInternal::BeforeSpread { ref mut index } => {
+                emitter.emit.init_elem_array(*index);
+                //      [stack] ARRAY
+
+                *index += 1;
+            }
+            ArrayEmitterStateInternal::AfterSpread => {
+                emitter.emit.init_elem_inc();
+                //      [stack] ARRAY INDEX+1
+            }
+        }
+
+        //              [stack] ARRAY INDEX?
+
+        Ok(())
+    }
+}
+
+/// Struct for emitting bytecode for an array element with hole.
+pub struct ArrayElisionEmitter<'a> {
+    pub state: &'a mut ArrayEmitterState,
+}
+
+impl<'a> ArrayElisionEmitter<'a> {
+    pub fn emit(self, emitter: &mut AstEmitter) {
+        //              [stack] ARRAY INDEX?
+
+        emitter.emit.hole();
+        //              [stack] ARRAY INDEX? HOLE
+
+        match &mut self.state.0 {
+            ArrayEmitterStateInternal::BeforeSpread { ref mut index } => {
+                emitter.emit.init_elem_array(*index);
+                //      [stack] ARRAY
+
+                *index += 1;
+            }
+            ArrayEmitterStateInternal::AfterSpread => {
+                emitter.emit.init_elem_inc();
+                //      [stack] ARRAY INDEX+1
+            }
+        }
+
+        //              [stack] ARRAY INDEX?
+    }
+}
+
+/// Struct for emitting bytecode for an array element with spread.
+pub struct ArraySpreadEmitter<'a, F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub state: &'a mut ArrayEmitterState,
+    pub elem: F,
+}
+
+impl<'a, F> ArraySpreadEmitter<'a, F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack] ARRAY INDEX?
+
+        match self.state.0 {
+            ArrayEmitterStateInternal::BeforeSpread { index } => {
+                emitter.emit.numeric(index as f64);
+            }
+            _ => {}
+        }
+        self.state.0 = ArrayEmitterStateInternal::AfterSpread;
+
+        //              [stack] ARRAY INDEX
+
+        Err(EmitError::NotImplemented("TODO: spread element"))
+    }
+}
+
+enum ArrayEmitterStateInternal {
+    BeforeSpread { index: u32 },
+    AfterSpread,
+}
+
+/// Opaque struct that can be created only by ArrayEmitter.
+/// This guarantees that Array*Emitter structs cannot be used outside
+/// of ArrayEmitter callback.
+pub struct ArrayEmitterState(ArrayEmitterStateInternal);
+
+impl ArrayEmitterState {
+    fn new() -> Self {
+        Self(ArrayEmitterStateInternal::BeforeSpread { index: 0 })
+    }
+}
+
+pub enum ArrayElementKind {
+    Normal,
+    Elision,
+    Spread,
+}
+
+/// Struct for emitting bytecode for an array expression.
+pub struct ArrayEmitter<'a, ElemT, ElemKindF, ElemF>
+where
+    ElemKindF: Fn(&ElemT) -> ArrayElementKind,
+    ElemF: Fn(&mut AstEmitter, &mut ArrayEmitterState, &'a ElemT) -> Result<(), EmitError>,
+{
+    pub elements: std::slice::Iter<'a, ElemT>,
+    pub elem_kind: ElemKindF,
+    pub elem: ElemF,
+}
+
+impl<'a, ElemT, ElemKindF, ElemF> ArrayEmitter<'a, ElemT, ElemKindF, ElemF>
+where
+    ElemKindF: Fn(&ElemT) -> ArrayElementKind,
+    ElemF: Fn(&mut AstEmitter, &mut ArrayEmitterState, &'a ElemT) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack]
+
+        // Initialize the array to its minimum possible length.
+        let min_length = self
+            .elements
+            .clone()
+            .map(|e| match (self.elem_kind)(e) {
+                ArrayElementKind::Normal => 1,
+                ArrayElementKind::Elision => 1,
+                ArrayElementKind::Spread => 0,
+            })
+            .sum::<u32>();
+
+        emitter.emit.new_array(min_length);
+        //              [stack] ARRAY
+
+        let mut state = ArrayEmitterState::new();
+        for element in self.elements {
+            (self.elem)(emitter, &mut state, element)?;
+            //          [stack] ARRAY INDEX?
+        }
+
+        match state.0 {
+            ArrayEmitterStateInternal::AfterSpread => {
+                //      [stack] ARRAY INDEX
+
+                emitter.emit.pop();
+                //      [stack] ARRAY
+            }
+            _ => {}
+        }
+
+        //              [stack] ARRAY
+
+        Ok(())
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/ast_emitter.rs b/third_party/rust/jsparagus-emitter/src/ast_emitter.rs
new file mode 100644
index 0000000000..287f5b8d35
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/ast_emitter.rs
@@ -0,0 +1,961 @@
+//! High-level bytecode emitter.
+//!
+//! Converts AST nodes to bytecode.
+
+use crate::array_emitter::*;
+use crate::block_emitter::BlockEmitter;
+use crate::compilation_info::CompilationInfo;
+use crate::emitter::{EmitError, EmitOptions, InstructionWriter};
+use crate::emitter_scope::{EmitterScopeStack, NameLocation};
+use crate::expression_emitter::*;
+use crate::function_declaration_emitter::{
+    AnnexBFunctionDeclarationEmitter, LazyFunctionEmitter, LexicalFunctionDeclarationEmitter,
+};
+use crate::object_emitter::*;
+use crate::reference_op_emitter::{
+    AssignmentEmitter, CallEmitter, DeclarationEmitter, ElemReferenceEmitter, GetElemEmitter,
+    GetNameEmitter, GetPropEmitter, GetSuperElemEmitter, GetSuperPropEmitter, NameReferenceEmitter,
+    NewEmitter, PropReferenceEmitter,
+};
+use crate::script_emitter::ScriptEmitter;
+use ast::source_atom_set::{CommonSourceAtomSetIndices, SourceAtomSetIndex};
+use ast::types::*;
+use stencil::opcode::Opcode;
+use stencil::regexp::RegExpItem;
+use stencil::result::EmitResult;
+use stencil::script::ScriptStencil;
+
+use crate::control_structures::{
+    BreakEmitter, CForEmitter, ContinueEmitter, ControlStructureStack, DoWhileEmitter,
+    ForwardJumpEmitter, JumpKind, LabelEmitter, WhileEmitter,
+};
+
+/// Emit a program, converting the AST directly to bytecode.
+pub fn emit_program<'alloc>(
+    ast: &Program,
+    options: &EmitOptions,
+    mut compilation_info: CompilationInfo<'alloc>,
+) -> Result<EmitResult<'alloc>, EmitError> {
+    let emitter = AstEmitter::new(options, &mut compilation_info);
+
+    let script = match ast {
+        Program::Script(script) => emitter.emit_script(script)?,
+        _ => {
+            return Err(EmitError::NotImplemented("TODO: modules"));
+        }
+    };
+
+    compilation_info.scripts.set_top_level(script);
+
+    Ok(EmitResult::new(
+        compilation_info.atoms.into(),
+        compilation_info.slices.into(),
+        compilation_info.scope_data_map.into(),
+        compilation_info.regexps.into(),
+        compilation_info.scripts.into(),
+        compilation_info.script_data_list.into(),
+    ))
+}
+
+pub struct AstEmitter<'alloc, 'opt> {
+    pub emit: InstructionWriter,
+    pub scope_stack: EmitterScopeStack,
+    pub options: &'opt EmitOptions,
+    pub compilation_info: &'opt mut CompilationInfo<'alloc>,
+    pub control_stack: ControlStructureStack,
+}
+
+impl<'alloc, 'opt> AstEmitter<'alloc, 'opt> {
+    fn new(
+        options: &'opt EmitOptions,
+        compilation_info: &'opt mut CompilationInfo<'alloc>,
+    ) -> Self {
+        Self {
+            emit: InstructionWriter::new(),
+            scope_stack: EmitterScopeStack::new(),
+            options,
+            compilation_info,
+            control_stack: ControlStructureStack::new(),
+        }
+    }
+
+    pub fn lookup_name(&mut self, name: SourceAtomSetIndex) -> NameLocation {
+        self.scope_stack.lookup_name(name)
+    }
+
+    pub fn lookup_name_in_var(&mut self, name: SourceAtomSetIndex) -> NameLocation {
+        self.scope_stack.lookup_name_in_var(name)
+    }
+
+    fn emit_script(mut self, ast: &Script) -> Result<ScriptStencil, EmitError> {
+        let scope_data_map = &self.compilation_info.scope_data_map;
+        let function_declarations = &self.compilation_info.function_declarations;
+
+        let scope_index = scope_data_map.get_global_index();
+        let scope_data = scope_data_map.get_global_at(scope_index);
+
+        let top_level_functions: Vec<&Function> = scope_data
+            .functions
+            .iter()
+            .map(|key| {
+                *function_declarations
+                    .get(key)
+                    .expect("function should exist")
+            })
+            .collect();
+
+        ScriptEmitter {
+            top_level_functions: top_level_functions.iter(),
+            top_level_function: |emitter, fun| emitter.emit_top_level_function_declaration(fun),
+            statements: ast.statements.iter(),
+            statement: |emitter, statement| emitter.emit_statement(statement),
+        }
+        .emit(&mut self)?;
+
+        let script = self.emit.into_stencil(
+            &mut self.compilation_info.script_data_list,
+            self.options.extent.clone(),
+        )?;
+
+        Ok(script)
+    }
+
+    fn emit_top_level_function_declaration(&mut self, fun: &Function) -> Result<(), EmitError> {
+        if fun.is_generator {
+            return Err(EmitError::NotImplemented("TODO: Generator"));
+        }
+        if fun.is_async {
+            return Err(EmitError::NotImplemented("TODO: Async function"));
+        }
+
+        let stencil_index = *self
+            .compilation_info
+            .function_stencil_indices
+            .get(fun)
+            .expect("ScriptStencil should be created");
+
+        // NOTE: GCIndex for the function is implicitly handled by
+        //       global_or_eval_decl_instantiation.
+        LazyFunctionEmitter { stencil_index }.emit(self);
+
+        Ok(())
+    }
+
+    fn emit_non_top_level_function_declaration(&mut self, fun: &Function) -> Result<(), EmitError> {
+        if fun.is_generator {
+            return Err(EmitError::NotImplemented("TODO: Generator"));
+        }
+        if fun.is_async {
+            return Err(EmitError::NotImplemented("TODO: Async function"));
+        }
+
+        let stencil_index = *self
+            .compilation_info
+            .function_stencil_indices
+            .get(fun)
+            .expect("ScriptStencil should be created");
+
+        let is_annex_b = self
+            .compilation_info
+            .function_declaration_properties
+            .is_annex_b(stencil_index);
+
+        let fun_index = LazyFunctionEmitter { stencil_index }.emit(self);
+
+        let name = self
+            .compilation_info
+            .scripts
+            .get(stencil_index)
+            .fun_name()
+            .expect("Function declaration should have name");
+
+        if is_annex_b {
+            AnnexBFunctionDeclarationEmitter { fun_index, name }.emit(self)?;
+        } else {
+            LexicalFunctionDeclarationEmitter { fun_index, name }.emit(self)?;
+        }
+
+        Ok(())
+    }
+
+    fn emit_statement(&mut self, ast: &Statement) -> Result<(), EmitError> {
+        match ast {
+            Statement::ClassDeclaration(_) => {
+                return Err(EmitError::NotImplemented("TODO: ClassDeclaration"));
+            }
+            Statement::BlockStatement { block, .. } => {
+                let scope_data_map = &self.compilation_info.scope_data_map;
+                let function_declarations = &self.compilation_info.function_declarations;
+
+                let scope_index = scope_data_map.get_index(block);
+                let scope_data = scope_data_map.get_lexical_at(scope_index);
+
+                let functions: Vec<&Function> = scope_data
+                    .functions
+                    .iter()
+                    .map(|key| {
+                        *function_declarations
+                            .get(key)
+                            .expect("function should exist")
+                    })
+                    .collect();
+
+                BlockEmitter {
+                    scope_index: self.compilation_info.scope_data_map.get_index(block),
+                    functions: functions.iter(),
+                    function: |emitter, fun| emitter.emit_non_top_level_function_declaration(fun),
+                    statements: block.statements.iter(),
+                    statement: |emitter, statement| emitter.emit_statement(statement),
+                }
+                .emit(self)?;
+            }
+            Statement::BreakStatement { label, .. } => {
+                BreakEmitter {
+                    label: label.as_ref().map(|x| x.value),
+                }
+                .emit(self);
+            }
+            Statement::ContinueStatement { label, .. } => {
+                ContinueEmitter {
+                    label: label.as_ref().map(|x| x.value),
+                }
+                .emit(self);
+            }
+            Statement::DebuggerStatement { .. } => {
+                self.emit.debugger();
+            }
+            Statement::DoWhileStatement { block, test, .. } => {
+                DoWhileEmitter {
+                    enclosing_emitter_scope_depth: self.scope_stack.current_depth(),
+                    block: |emitter| emitter.emit_statement(block),
+                    test: |emitter| emitter.emit_expression(test),
+                }
+                .emit(self)?;
+            }
+            Statement::EmptyStatement { .. } => (),
+            Statement::ExpressionStatement(ast) => {
+                ExpressionEmitter {
+                    expr: |emitter| emitter.emit_expression(ast),
+                }
+                .emit(self)?;
+            }
+            Statement::ForInStatement { .. } => {
+                return Err(EmitError::NotImplemented("TODO: ForInStatement"));
+            }
+            Statement::ForOfStatement { .. } => {
+                return Err(EmitError::NotImplemented("TODO: ForOfStatement"));
+            }
+            Statement::ForStatement {
+                init,
+                test,
+                update,
+                block,
+                ..
+            } => {
+                CForEmitter {
+                    enclosing_emitter_scope_depth: self.scope_stack.current_depth(),
+                    maybe_init: init,
+                    maybe_test: test,
+                    maybe_update: update,
+                    init: |emitter, val| match val {
+                        VariableDeclarationOrExpression::VariableDeclaration(ast) => {
+                            emitter.emit_variable_declaration_statement(ast)
+                        }
+                        VariableDeclarationOrExpression::Expression(expr) => {
+                            emitter.emit_expression(expr)?;
+                            emitter.emit.pop();
+                            Ok(())
+                        }
+                    },
+                    test: |emitter, expr| emitter.emit_expression(expr),
+                    update: |emitter, expr| {
+                        emitter.emit_expression(expr)?;
+                        emitter.emit.pop();
+                        Ok(())
+                    },
+                    block: |emitter| emitter.emit_statement(block),
+                }
+                .emit(self)?;
+            }
+            Statement::IfStatement(if_statement) => {
+                self.emit_if(if_statement)?;
+            }
+            Statement::LabelledStatement { label, body, .. } => {
+                LabelEmitter {
+                    enclosing_emitter_scope_depth: self.scope_stack.current_depth(),
+                    name: label.value,
+                    body: |emitter| emitter.emit_statement(body),
+                }
+                .emit(self)?;
+            }
+            Statement::ReturnStatement { .. } => {
+                return Err(EmitError::NotImplemented("TODO: ReturnStatement"));
+            }
+            Statement::SwitchStatement { .. } => {
+                return Err(EmitError::NotImplemented("TODO: SwitchStatement"));
+            }
+            Statement::SwitchStatementWithDefault { .. } => {
+                return Err(EmitError::NotImplemented(
+                    "TODO: SwitchStatementWithDefault",
+                ));
+            }
+            Statement::ThrowStatement { expression, .. } => {
+                self.emit_expression(expression)?;
+                self.emit.throw_();
+            }
+            Statement::TryCatchStatement { .. } => {
+                return Err(EmitError::NotImplemented("TODO: TryCatchStatement"));
+            }
+            Statement::TryFinallyStatement { .. } => {
+                return Err(EmitError::NotImplemented("TODO: TryFinallyStatement"));
+            }
+            Statement::VariableDeclarationStatement(ast) => {
+                self.emit_variable_declaration_statement(ast)?;
+            }
+            Statement::WhileStatement { test, block, .. } => {
+                WhileEmitter {
+                    enclosing_emitter_scope_depth: self.scope_stack.current_depth(),
+                    test: |emitter| emitter.emit_expression(test),
+                    block: |emitter| emitter.emit_statement(block),
+                }
+                .emit(self)?;
+            }
+            Statement::WithStatement { .. } => {
+                return Err(EmitError::NotImplemented("TODO: WithStatement"));
+            }
+            Statement::FunctionDeclaration(_) => {}
+        };
+
+        Ok(())
+    }
+
+    fn emit_variable_declaration_statement(
+        &mut self,
+        ast: &VariableDeclaration,
+    ) -> Result<(), EmitError> {
+        match ast.kind {
+            VariableDeclarationKind::Var { .. } => {}
+            VariableDeclarationKind::Let { .. } | VariableDeclarationKind::Const { .. } => {}
+        }
+
+        for decl in &ast.declarators {
+            if let Some(init) = &decl.init {
+                self.emit_declaration_assignment(&decl.binding, &init)?;
+            }
+        }
+
+        Ok(())
+    }
+
+    fn emit_declaration_assignment(
+        &mut self,
+        binding: &Binding,
+        init: &Expression,
+    ) -> Result<(), EmitError> {
+        match binding {
+            Binding::BindingIdentifier(binding) => {
+                let name = binding.name.value;
+                DeclarationEmitter {
+                    lhs: |emitter| Ok(NameReferenceEmitter { name }.emit_for_declaration(emitter)),
+                    rhs: |emitter| emitter.emit_expression(init),
+                }
+                .emit(self)?;
+                self.emit.pop();
+            }
+            _ => {
+                return Err(EmitError::NotImplemented("BindingPattern"));
+            }
+        }
+
+        Ok(())
+    }
+
+    fn emit_this(&mut self) -> Result<(), EmitError> {
+        Err(EmitError::NotImplemented("TODO: this"))
+    }
+
+    fn emit_if(&mut self, if_statement: &IfStatement) -> Result<(), EmitError> {
+        self.emit_expression(&if_statement.test)?;
+
+        let alternate_jump = ForwardJumpEmitter {
+            jump: JumpKind::JumpIfFalse,
+        }
+        .emit(self);
+
+        // Then branch
+        self.emit.jump_target();
+        self.emit_statement(&if_statement.consequent)?;
+
+        if let Some(alternate) = &if_statement.alternate {
+            let then_jump = ForwardJumpEmitter {
+                jump: JumpKind::Goto,
+            }
+            .emit(self);
+            // ^^ part of then branch
+
+            // Else branch
+            alternate_jump.patch_not_merge(self);
+            self.emit_statement(alternate)?;
+
+            // Merge point after else
+            then_jump.patch_merge(self);
+        } else {
+            // Merge point without else
+            alternate_jump.patch_merge(self);
+        }
+
+        Ok(())
+    }
+
+    fn emit_expression(&mut self, ast: &Expression) -> Result<(), EmitError> {
+        match ast {
+            Expression::ClassExpression(_) => {
+                return Err(EmitError::NotImplemented("TODO: ClassExpression"));
+            }
+
+            Expression::LiteralBooleanExpression { value, .. } => {
+                self.emit.emit_boolean(*value);
+            }
+
+            Expression::LiteralInfinityExpression { .. } => {
+                self.emit.double_(std::f64::INFINITY);
+            }
+
+            Expression::LiteralNullExpression { .. } => {
+                self.emit.null();
+            }
+
+            Expression::LiteralNumericExpression(num) => {
+                self.emit.numeric(num.value);
+            }
+
+            Expression::LiteralRegExpExpression {
+                pattern,
+                global,
+                ignore_case,
+                multi_line,
+                dot_all,
+                sticky,
+                unicode,
+                ..
+            } => {
+                let item = RegExpItem {
+                    pattern: *pattern,
+                    global: *global,
+                    ignore_case: *ignore_case,
+                    multi_line: *multi_line,
+                    dot_all: *dot_all,
+                    sticky: *sticky,
+                    unicode: *unicode,
+                };
+                let regexp_index = self.compilation_info.regexps.push(item);
+                let index = self.emit.get_regexp_gcthing_index(regexp_index);
+                self.emit.reg_exp(index);
+            }
+
+            Expression::LiteralStringExpression { value, .. } => {
+                let str_index = self.emit.get_atom_gcthing_index(*value);
+                self.emit.string(str_index);
+            }
+
+            Expression::ArrayExpression(ast) => {
+                self.emit_array_expression(ast)?;
+            }
+
+            Expression::ArrowExpression { .. } => {
+                return Err(EmitError::NotImplemented("TODO: ArrowExpression"));
+            }
+
+            Expression::AssignmentExpression {
+                binding,
+                expression,
+                ..
+            } => {
+                self.emit_assignment_expression(binding, expression)?;
+            }
+
+            Expression::BinaryExpression {
+                operator,
+                left,
+                right,
+                ..
+            } => {
+                self.emit_binary_expression(operator, left, right)?;
+            }
+
+            Expression::CallExpression(CallExpression {
+                callee, arguments, ..
+            }) => {
+                self.emit_call_expression(callee, arguments)?;
+            }
+
+            Expression::CompoundAssignmentExpression { .. } => {
+                return Err(EmitError::NotImplemented(
+                    "TODO: CompoundAssignmentExpression",
+                ));
+            }
+
+            Expression::ConditionalExpression {
+                test,
+                consequent,
+                alternate,
+                ..
+            } => {
+                self.emit_conditional_expression(test, consequent, alternate)?;
+            }
+
+            Expression::FunctionExpression(_) => {
+                return Err(EmitError::NotImplemented("TODO: FunctionExpression"));
+            }
+
+            Expression::IdentifierExpression(ast) => {
+                self.emit_identifier_expression(ast);
+            }
+
+            Expression::MemberExpression(ast) => {
+                self.emit_member_expression(ast)?;
+            }
+
+            Expression::NewExpression {
+                callee, arguments, ..
+            } => {
+                self.emit_new_expression(callee, arguments)?;
+            }
+
+            Expression::NewTargetExpression { .. } => {
+                return Err(EmitError::NotImplemented("TODO: NewTargetExpression"));
+            }
+
+            Expression::ObjectExpression(ast) => {
+                self.emit_object_expression(ast)?;
+            }
+
+            Expression::OptionalChain { .. } => {
+                return Err(EmitError::NotImplemented("TODO: OptionalChain"));
+            }
+
+            Expression::OptionalExpression { .. } => {
+                return Err(EmitError::NotImplemented("TODO: OptionalExpression"));
+            }
+
+            Expression::UnaryExpression {
+                operator, operand, ..
+            } => {
+                let opcode = match operator {
+                    UnaryOperator::Plus { .. } => Opcode::Pos,
+                    UnaryOperator::Minus { .. } => Opcode::Neg,
+                    UnaryOperator::LogicalNot { .. } => Opcode::Not,
+                    UnaryOperator::BitwiseNot { .. } => Opcode::BitNot,
+                    UnaryOperator::Void { .. } => Opcode::Void,
+                    UnaryOperator::Typeof { .. } => {
+                        return Err(EmitError::NotImplemented("TODO: Typeof"));
+                    }
+                    UnaryOperator::Delete { .. } => {
+                        return Err(EmitError::NotImplemented("TODO: Delete"));
+                    }
+                };
+                self.emit_expression(operand)?;
+                self.emit.emit_unary_op(opcode);
+            }
+
+            Expression::TemplateExpression(_) => {
+                return Err(EmitError::NotImplemented("TODO: TemplateExpression"));
+            }
+
+            Expression::ThisExpression { .. } => {
+                self.emit_this()?;
+            }
+
+            Expression::UpdateExpression { .. } => {
+                return Err(EmitError::NotImplemented("TODO: UpdateExpression"));
+            }
+
+            Expression::YieldExpression { .. } => {
+                return Err(EmitError::NotImplemented("TODO: YieldExpression"));
+            }
+
+            Expression::YieldGeneratorExpression { .. } => {
+                return Err(EmitError::NotImplemented("TODO: YieldGeneratorExpression"));
+            }
+
+            Expression::AwaitExpression { .. } => {
+                return Err(EmitError::NotImplemented("TODO: AwaitExpression"));
+            }
+
+            Expression::ImportCallExpression { .. } => {
+                return Err(EmitError::NotImplemented("TODO: ImportCallExpression"));
+            }
+        }
+
+        Ok(())
+    }
+
+    fn emit_binary_expression(
+        &mut self,
+        operator: &BinaryOperator,
+        left: &Expression,
+        right: &Expression,
+    ) -> Result<(), EmitError> {
+        let opcode = match operator {
+            BinaryOperator::Equals { .. } => Opcode::Eq,
+            BinaryOperator::NotEquals { .. } => Opcode::Ne,
+            BinaryOperator::StrictEquals { .. } => Opcode::StrictEq,
+            BinaryOperator::StrictNotEquals { .. } => Opcode::StrictNe,
+            BinaryOperator::LessThan { .. } => Opcode::Lt,
+            BinaryOperator::LessThanOrEqual { .. } => Opcode::Le,
+            BinaryOperator::GreaterThan { .. } => Opcode::Gt,
+            BinaryOperator::GreaterThanOrEqual { .. } => Opcode::Ge,
+            BinaryOperator::In { .. } => Opcode::In,
+            BinaryOperator::Instanceof { .. } => Opcode::Instanceof,
+            BinaryOperator::LeftShift { .. } => Opcode::Lsh,
+            BinaryOperator::RightShift { .. } => Opcode::Rsh,
+            BinaryOperator::RightShiftExt { .. } => Opcode::Ursh,
+            BinaryOperator::Add { .. } => Opcode::Add,
+            BinaryOperator::Sub { .. } => Opcode::Sub,
+            BinaryOperator::Mul { .. } => Opcode::Mul,
+            BinaryOperator::Div { .. } => Opcode::Div,
+            BinaryOperator::Mod { .. } => Opcode::Mod,
+            BinaryOperator::Pow { .. } => Opcode::Pow,
+            BinaryOperator::BitwiseOr { .. } => Opcode::BitOr,
+            BinaryOperator::BitwiseXor { .. } => Opcode::BitXor,
+            BinaryOperator::BitwiseAnd { .. } => Opcode::BitAnd,
+
+            BinaryOperator::Coalesce { .. } => {
+                self.emit_short_circuit(JumpKind::Coalesce, left, right)?;
+                return Ok(());
+            }
+            BinaryOperator::LogicalOr { .. } => {
+                self.emit_short_circuit(JumpKind::LogicalOr, left, right)?;
+                return Ok(());
+            }
+            BinaryOperator::LogicalAnd { .. } => {
+                self.emit_short_circuit(JumpKind::LogicalAnd, left, right)?;
+                return Ok(());
+            }
+
+            BinaryOperator::Comma { .. } => {
+                self.emit_expression(left)?;
+                self.emit.pop();
+                self.emit_expression(right)?;
+                return Ok(());
+            }
+        };
+
+        self.emit_expression(left)?;
+        self.emit_expression(right)?;
+        self.emit.emit_binary_op(opcode);
+        Ok(())
+    }
+
+    fn emit_short_circuit(
+        &mut self,
+        jump: JumpKind,
+        left: &Expression,
+        right: &Expression,
+    ) -> Result<(), EmitError> {
+        self.emit_expression(left)?;
+        let jump = ForwardJumpEmitter { jump: jump }.emit(self);
+        self.emit.pop();
+        self.emit_expression(right)?;
+        jump.patch_merge(self);
+        return Ok(());
+    }
+
+    fn emit_object_expression(&mut self, object: &ObjectExpression) -> Result<(), EmitError> {
+        ObjectEmitter {
+            properties: object.properties.iter(),
+            prop: |emitter, state, prop| emitter.emit_object_property(state, prop),
+        }
+        .emit(self)
+    }
+
+    fn emit_object_property(
+        &mut self,
+        state: &mut ObjectEmitterState,
+        property: &ObjectProperty,
+    ) -> Result<(), EmitError> {
+        match property {
+            ObjectProperty::NamedObjectProperty(NamedObjectProperty::DataProperty(
+                DataProperty {
+                    property_name,
+                    expression: prop_value,
+                    ..
+                },
+            )) => match property_name {
+                PropertyName::StaticPropertyName(StaticPropertyName { value, .. }) => {
+                    NamePropertyEmitter {
+                        state,
+                        key: *value,
+                        value: |emitter| emitter.emit_expression(prop_value),
+                    }
+                    .emit(self)?;
+                }
+                PropertyName::StaticNumericPropertyName(NumericLiteral { value, .. }) => {
+                    IndexPropertyEmitter {
+                        state,
+                        key: *value,
+                        value: |emitter| emitter.emit_expression(prop_value),
+                    }
+                    .emit(self)?;
+                }
+                PropertyName::ComputedPropertyName(ComputedPropertyName {
+                    expression: prop_key,
+                    ..
+                }) => {
+                    ComputedPropertyEmitter {
+                        state,
+                        key: |emitter| emitter.emit_expression(prop_key),
+                        value: |emitter| emitter.emit_expression(prop_value),
+                    }
+                    .emit(self)?;
+                }
+            },
+            _ => return Err(EmitError::NotImplemented("TODO: non data property")),
+        }
+        Ok(())
+    }
+
+    fn emit_array_expression(&mut self, array: &ArrayExpression) -> Result<(), EmitError> {
+        ArrayEmitter {
+            elements: array.elements.iter(),
+            elem_kind: |e| match e {
+                ArrayExpressionElement::Expression(..) => ArrayElementKind::Normal,
+                ArrayExpressionElement::Elision { .. } => ArrayElementKind::Elision,
+                ArrayExpressionElement::SpreadElement(..) => ArrayElementKind::Spread,
+            },
+            elem: |emitter, state, elem| {
+                match elem {
+                    ArrayExpressionElement::Expression(expr) => {
+                        ArrayElementEmitter {
+                            state,
+                            elem: |emitter| emitter.emit_expression(expr),
+                        }
+                        .emit(emitter)?;
+                    }
+                    ArrayExpressionElement::Elision { .. } => {
+                        ArrayElisionEmitter { state }.emit(emitter);
+                    }
+                    ArrayExpressionElement::SpreadElement(expr) => {
+                        ArraySpreadEmitter {
+                            state,
+                            elem: |emitter| emitter.emit_expression(expr),
+                        }
+                        .emit(emitter)?;
+                    }
+                }
+                Ok(())
+            },
+        }
+        .emit(self)
+    }
+
+    fn emit_conditional_expression(
+        &mut self,
+        test: &Expression,
+        consequent: &Expression,
+        alternate: &Expression,
+    ) -> Result<(), EmitError> {
+        self.emit_expression(test)?;
+
+        let else_jump = ForwardJumpEmitter {
+            jump: JumpKind::JumpIfFalse,
+        }
+        .emit(self);
+
+        // Then branch
+        self.emit.jump_target();
+        self.emit_expression(consequent)?;
+
+        let finally_jump = ForwardJumpEmitter {
+            jump: JumpKind::Goto,
+        }
+        .emit(self);
+
+        // Else branch
+        else_jump.patch_not_merge(self);
+        self.emit_expression(alternate)?;
+
+        // Merge point
+        finally_jump.patch_merge(self);
+
+        Ok(())
+    }
+
+    fn emit_assignment_expression(
+        &mut self,
+        binding: &AssignmentTarget,
+        expression: &Expression,
+    ) -> Result<(), EmitError> {
+        AssignmentEmitter {
+            lhs: |emitter| match binding {
+                AssignmentTarget::SimpleAssignmentTarget(
+                    SimpleAssignmentTarget::AssignmentTargetIdentifier(
+                        AssignmentTargetIdentifier { name, .. },
+                    ),
+                ) => Ok(NameReferenceEmitter { name: name.value }.emit_for_assignment(emitter)),
+                _ => Err(EmitError::NotImplemented(
+                    "non-identifier assignment target",
+                )),
+            },
+            rhs: |emitter| emitter.emit_expression(expression),
+        }
+        .emit(self)
+    }
+
+    fn emit_identifier_expression(&mut self, ast: &IdentifierExpression) {
+        let name = ast.name.value;
+        GetNameEmitter { name }.emit(self);
+    }
+
+    fn emit_member_expression(&mut self, ast: &MemberExpression) -> Result<(), EmitError> {
+        match ast {
+            MemberExpression::ComputedMemberExpression(ComputedMemberExpression {
+                object: ExpressionOrSuper::Expression(object),
+                expression,
+                ..
+            }) => GetElemEmitter {
+                obj: |emitter| emitter.emit_expression(object),
+                key: |emitter| emitter.emit_expression(expression),
+            }
+            .emit(self),
+
+            MemberExpression::ComputedMemberExpression(ComputedMemberExpression {
+                object: ExpressionOrSuper::Super { .. },
+                expression,
+                ..
+            }) => GetSuperElemEmitter {
+                this: |emitter| emitter.emit_this(),
+                key: |emitter| emitter.emit_expression(expression),
+            }
+            .emit(self),
+
+            MemberExpression::StaticMemberExpression(StaticMemberExpression {
+                object: ExpressionOrSuper::Expression(object),
+                property,
+                ..
+            }) => GetPropEmitter {
+                obj: |emitter| emitter.emit_expression(object),
+                key: property.value,
+            }
+            .emit(self),
+
+            MemberExpression::StaticMemberExpression(StaticMemberExpression {
+                object: ExpressionOrSuper::Super { .. },
+                property,
+                ..
+            }) => GetSuperPropEmitter {
+                this: |emitter| emitter.emit_this(),
+                key: property.value,
+            }
+            .emit(self),
+
+            MemberExpression::PrivateFieldExpression(PrivateFieldExpression { .. }) => {
+                Err(EmitError::NotImplemented("PrivateFieldExpression"))
+            }
+        }
+    }
+
+    fn emit_new_expression(
+        &mut self,
+        callee: &Expression,
+        arguments: &Arguments,
+    ) -> Result<(), EmitError> {
+        for arg in &arguments.args {
+            if let Argument::SpreadElement(_) = arg {
+                return Err(EmitError::NotImplemented("TODO: SpreadNew"));
+            }
+        }
+
+        NewEmitter {
+            callee: |emitter| emitter.emit_expression(callee),
+            arguments: |emitter| {
+                emitter.emit_arguments(arguments)?;
+                Ok(arguments.args.len())
+            },
+        }
+        .emit(self)?;
+
+        Ok(())
+    }
+
+    fn emit_call_expression(
+        &mut self,
+        callee: &ExpressionOrSuper,
+        arguments: &Arguments,
+    ) -> Result<(), EmitError> {
+        // Don't do super handling in an emit_expresion_or_super because the bytecode heavily
+        // depends on how you're using the super
+
+        CallEmitter {
+            callee: |emitter| match callee {
+                ExpressionOrSuper::Expression(expr) => match &**expr {
+                    Expression::IdentifierExpression(IdentifierExpression { name, .. }) => {
+                        if name.value == CommonSourceAtomSetIndices::eval() {
+                            return Err(EmitError::NotImplemented("TODO: direct eval"));
+                        }
+                        Ok(NameReferenceEmitter { name: name.value }.emit_for_call(emitter))
+                    }
+
+                    Expression::MemberExpression(MemberExpression::StaticMemberExpression(
+                        StaticMemberExpression {
+                            object: ExpressionOrSuper::Expression(object),
+                            property,
+                            ..
+                        },
+                    )) => PropReferenceEmitter {
+                        obj: |emitter| emitter.emit_expression(object),
+                        key: property.value,
+                    }
+                    .emit_for_call(emitter),
+
+                    Expression::MemberExpression(MemberExpression::ComputedMemberExpression(
+                        ComputedMemberExpression {
+                            object: ExpressionOrSuper::Expression(object),
+                            expression,
+                            ..
+                        },
+                    )) => ElemReferenceEmitter {
+                        obj: |emitter| emitter.emit_expression(object),
+                        key: |emitter| emitter.emit_expression(expression),
+                    }
+                    .emit_for_call(emitter),
+
+                    _ => {
+                        return Err(EmitError::NotImplemented(
+                            "TODO: Call (only global functions are supported)",
+                        ));
+                    }
+                },
+                _ => {
+                    return Err(EmitError::NotImplemented("TODO: Super"));
+                }
+            },
+            arguments: |emitter| {
+                emitter.emit_arguments(arguments)?;
+                Ok(arguments.args.len())
+            },
+        }
+        .emit(self)?;
+
+        Ok(())
+    }
+
+    fn emit_arguments(&mut self, ast: &Arguments) -> Result<(), EmitError> {
+        for argument in &ast.args {
+            self.emit_argument(argument)?;
+        }
+
+        Ok(())
+    }
+
+    fn emit_argument(&mut self, ast: &Argument) -> Result<(), EmitError> {
+        match ast {
+            Argument::Expression(ast) => self.emit_expression(ast)?,
+            Argument::SpreadElement(_) => {
+                return Err(EmitError::NotImplemented("TODO: SpreadElement"));
+            }
+        }
+
+        Ok(())
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/block_emitter.rs b/third_party/rust/jsparagus-emitter/src/block_emitter.rs
new file mode 100644
index 0000000000..b6400a5832
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/block_emitter.rs
@@ -0,0 +1,41 @@
+use crate::ast_emitter::AstEmitter;
+use crate::emitter::EmitError;
+use stencil::scope::ScopeIndex;
+
+pub struct BlockEmitter<'a, FuncT, FuncF, StmtT, StmtF>
+where
+    FuncF: Fn(&mut AstEmitter, &FuncT) -> Result<(), EmitError>,
+    StmtF: Fn(&mut AstEmitter, &StmtT) -> Result<(), EmitError>,
+{
+    pub scope_index: ScopeIndex,
+    pub functions: std::slice::Iter<'a, FuncT>,
+    pub function: FuncF,
+    pub statements: std::slice::Iter<'a, StmtT>,
+    pub statement: StmtF,
+}
+
+impl<'a, FuncT, FuncF, StmtT, StmtF> BlockEmitter<'a, FuncT, FuncF, StmtT, StmtF>
+where
+    FuncF: Fn(&mut AstEmitter, &FuncT) -> Result<(), EmitError>,
+    StmtF: Fn(&mut AstEmitter, &StmtT) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        emitter.scope_stack.enter_lexical(
+            &mut emitter.emit,
+            &mut emitter.compilation_info.scope_data_map,
+            self.scope_index,
+        );
+
+        for fun in self.functions {
+            (self.function)(emitter, fun)?;
+        }
+
+        for statement in self.statements {
+            (self.statement)(emitter, statement)?;
+        }
+
+        emitter.scope_stack.leave_lexical(&mut emitter.emit);
+
+        Ok(())
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/compilation_info.rs b/third_party/rust/jsparagus-emitter/src/compilation_info.rs
new file mode 100644
index 0000000000..1feeb70862
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/compilation_info.rs
@@ -0,0 +1,45 @@
+use ast::associated_data::AssociatedData;
+use ast::source_atom_set::SourceAtomSet;
+use ast::source_slice_list::SourceSliceList;
+use ast::types::Function;
+use scope::data::FunctionDeclarationPropertyMap;
+use std::collections::HashMap;
+use stencil::regexp::RegExpList;
+use stencil::scope::ScopeDataMap;
+use stencil::script::{ImmutableScriptDataList, ScriptStencilIndex, ScriptStencilList};
+
+pub struct CompilationInfo<'alloc> {
+    pub atoms: SourceAtomSet<'alloc>,
+    pub slices: SourceSliceList<'alloc>,
+    pub regexps: RegExpList,
+    pub scope_data_map: ScopeDataMap,
+    pub function_declarations: HashMap<ScriptStencilIndex, &'alloc Function<'alloc>>,
+    pub function_stencil_indices: AssociatedData<ScriptStencilIndex>,
+    pub function_declaration_properties: FunctionDeclarationPropertyMap,
+    pub scripts: ScriptStencilList,
+    pub script_data_list: ImmutableScriptDataList,
+}
+
+impl<'alloc> CompilationInfo<'alloc> {
+    pub fn new(
+        atoms: SourceAtomSet<'alloc>,
+        slices: SourceSliceList<'alloc>,
+        scope_data_map: ScopeDataMap,
+        function_declarations: HashMap<ScriptStencilIndex, &'alloc Function<'alloc>>,
+        function_stencil_indices: AssociatedData<ScriptStencilIndex>,
+        function_declaration_properties: FunctionDeclarationPropertyMap,
+        scripts: ScriptStencilList,
+    ) -> Self {
+        Self {
+            atoms,
+            slices,
+            regexps: RegExpList::new(),
+            scope_data_map,
+            function_declarations,
+            function_stencil_indices,
+            function_declaration_properties,
+            scripts,
+            script_data_list: ImmutableScriptDataList::new(),
+        }
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/control_structures.rs b/third_party/rust/jsparagus-emitter/src/control_structures.rs
new file mode 100644
index 0000000000..f19f423434
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/control_structures.rs
@@ -0,0 +1,708 @@
+use crate::ast_emitter::AstEmitter;
+use crate::emitter::EmitError;
+use crate::emitter::InstructionWriter;
+use crate::emitter_scope::{EmitterScope, EmitterScopeDepth};
+use ast::source_atom_set::SourceAtomSetIndex;
+use stencil::bytecode_offset::{BytecodeOffset, BytecodeOffsetDiff};
+
+// Control structures
+
+#[derive(Debug)]
+pub enum JumpKind {
+    Coalesce,
+    LogicalAnd,
+    LogicalOr,
+    JumpIfFalse,
+    Goto,
+}
+
+trait Jump {
+    fn jump_kind(&mut self) -> &JumpKind {
+        &JumpKind::Goto
+    }
+
+    fn should_fallthrough(&mut self) -> bool {
+        // a fallthrough occurs if the jump is a conditional jump and if the
+        // condition doesn't met, the execution goes to the next opcode
+        // instead of the target of the jump.
+        match self.jump_kind() {
+            JumpKind::Coalesce { .. }
+            | JumpKind::LogicalOr { .. }
+            | JumpKind::LogicalAnd { .. }
+            | JumpKind::JumpIfFalse { .. } => true,
+
+            JumpKind::Goto { .. } => false,
+        }
+    }
+
+    fn emit_jump(&mut self, emitter: &mut AstEmitter) {
+        // in the c++ bytecode emitter, the jumplist is emitted
+        // and four bytes are used in order to save memory. We are not using that
+        // here, so instead we are using a placeholder offset set to 0, which will
+        // be updated later in patch_and_emit_jump_target.
+        let placeholder_offset = BytecodeOffsetDiff::uninitialized();
+        match self.jump_kind() {
+            JumpKind::Coalesce { .. } => {
+                emitter.emit.coalesce(placeholder_offset);
+            }
+            JumpKind::LogicalOr { .. } => {
+                emitter.emit.or_(placeholder_offset);
+            }
+            JumpKind::LogicalAnd { .. } => {
+                emitter.emit.and_(placeholder_offset);
+            }
+            JumpKind::JumpIfFalse { .. } => {
+                emitter.emit.jump_if_false(placeholder_offset);
+            }
+            JumpKind::Goto { .. } => {
+                emitter.emit.goto_(placeholder_offset);
+            }
+        }
+
+        // The JITs rely on a jump target being emitted after the
+        // conditional jump
+        if self.should_fallthrough() {
+            emitter.emit.jump_target();
+        }
+    }
+}
+
+#[derive(Debug)]
+#[must_use]
+pub struct JumpPatchEmitter {
+    offsets: Vec<BytecodeOffset>,
+    depth: usize,
+}
+
+impl JumpPatchEmitter {
+    pub fn patch_merge(self, emitter: &mut AstEmitter) {
+        emitter.emit.emit_jump_target_and_patch(&self.offsets);
+
+        // If the previous opcode fall-through, it should have the same stack
+        // depth.
+        debug_assert!(emitter.emit.stack_depth() == self.depth);
+    }
+
+    pub fn patch_not_merge(self, emitter: &mut AstEmitter) {
+        emitter.emit.emit_jump_target_and_patch(&self.offsets);
+        // If the previous opcode doesn't fall-through, overwrite the stack
+        // depth.
+        emitter.emit.set_stack_depth(self.depth);
+    }
+}
+
+// Struct for emitting bytecode for forward jump.
+#[derive(Debug)]
+pub struct ForwardJumpEmitter {
+    pub jump: JumpKind,
+}
+impl Jump for ForwardJumpEmitter {
+    fn jump_kind(&mut self) -> &JumpKind {
+        &self.jump
+    }
+}
+
+impl ForwardJumpEmitter {
+    pub fn emit(&mut self, emitter: &mut AstEmitter) -> JumpPatchEmitter {
+        let offsets = vec![emitter.emit.bytecode_offset()];
+        self.emit_jump(emitter);
+        let depth = emitter.emit.stack_depth();
+
+        JumpPatchEmitter { offsets, depth }
+    }
+}
+
+pub trait Breakable {
+    fn register_break(&mut self, offset: BytecodeOffset);
+    fn emit_break_target_and_patch(&mut self, emit: &mut InstructionWriter);
+}
+
+pub trait Continuable {
+    fn register_continue(&mut self, offset: BytecodeOffset);
+
+    fn emit_continue_target_and_patch(&mut self, emit: &mut InstructionWriter);
+}
+
+#[derive(Debug, PartialEq)]
+pub struct LoopControl {
+    enclosing_emitter_scope_depth: EmitterScopeDepth,
+    breaks: Vec<BytecodeOffset>,
+    continues: Vec<BytecodeOffset>,
+    head: BytecodeOffset,
+}
+
+impl Breakable for LoopControl {
+    fn register_break(&mut self, offset: BytecodeOffset) {
+        // offset points to the location of the jump, which will need to be updated
+        // once we emit the jump target in emit_jump_target_and_patch
+        self.breaks.push(offset);
+    }
+
+    fn emit_break_target_and_patch(&mut self, emit: &mut InstructionWriter) {
+        emit.emit_jump_target_and_patch(&self.breaks);
+    }
+}
+
+impl Continuable for LoopControl {
+    fn register_continue(&mut self, offset: BytecodeOffset) {
+        // offset points to the location of the jump, which will need to be updated
+        // once we emit the jump target in emit_jump_target_and_patch
+        self.continues.push(offset);
+    }
+
+    fn emit_continue_target_and_patch(&mut self, emit: &mut InstructionWriter) {
+        emit.emit_jump_target_and_patch(&self.continues);
+    }
+}
+
+impl LoopControl {
+    pub fn new(
+        emit: &mut InstructionWriter,
+        depth: u8,
+        enclosing_emitter_scope_depth: EmitterScopeDepth,
+    ) -> Self {
+        let offset = LoopControl::open_loop(emit, depth);
+        Self {
+            enclosing_emitter_scope_depth,
+            breaks: Vec::new(),
+            continues: Vec::new(),
+            head: offset,
+        }
+    }
+
+    fn open_loop(emit: &mut InstructionWriter, depth: u8) -> BytecodeOffset {
+        // Insert a Nop if needed to ensure the script does not start with a
+        // JSOp::LoopHead. This avoids JIT issues with prologue code + try notes
+        // or OSR. See bug 1602390 and bug 1602681.
+        let mut offset = emit.bytecode_offset();
+        if offset.offset == 0 {
+            emit.nop();
+            offset = emit.bytecode_offset();
+        }
+        // emit the jump target for the loop head
+        emit.loop_head(depth);
+        offset
+    }
+
+    pub fn close_loop(&mut self, emit: &mut InstructionWriter) {
+        let offset = emit.bytecode_offset();
+        let diff_to_head = self.head.diff_from(offset);
+
+        emit.goto_(diff_to_head);
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub struct LabelControl {
+    enclosing_emitter_scope_depth: EmitterScopeDepth,
+    name: SourceAtomSetIndex,
+    breaks: Vec<BytecodeOffset>,
+    head: BytecodeOffset,
+}
+
+impl Breakable for LabelControl {
+    fn register_break(&mut self, offset: BytecodeOffset) {
+        // offset points to the location of the jump, which will need to be updated
+        // once we emit the jump target in emit_jump_target_and_patch
+        self.breaks.push(offset);
+    }
+
+    fn emit_break_target_and_patch(&mut self, emit: &mut InstructionWriter) {
+        if !self.breaks.is_empty() {
+            emit.emit_jump_target_and_patch(&self.breaks);
+        }
+    }
+}
+
+impl LabelControl {
+    pub fn new(
+        name: SourceAtomSetIndex,
+        emit: &mut InstructionWriter,
+        enclosing_emitter_scope_depth: EmitterScopeDepth,
+    ) -> Self {
+        let offset = emit.bytecode_offset();
+        Self {
+            enclosing_emitter_scope_depth,
+            name,
+            head: offset,
+            breaks: Vec::new(),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub enum Control {
+    Loop(LoopControl),
+    Label(LabelControl),
+}
+
+impl Control {
+    fn enclosing_emitter_scope_depth(&self) -> EmitterScopeDepth {
+        match self {
+            Control::Loop(control) => control.enclosing_emitter_scope_depth,
+            Control::Label(control) => control.enclosing_emitter_scope_depth,
+        }
+    }
+}
+
+// Compared to C++ impl, this uses explicit stack struct,
+// given Rust cannot store a reference of stack-allocated object into
+// another object that has longer-lifetime.
+pub struct ControlStructureStack {
+    control_stack: Vec<Control>,
+}
+
+impl ControlStructureStack {
+    pub fn new() -> Self {
+        Self {
+            control_stack: Vec::new(),
+        }
+    }
+
+    pub fn open_loop(
+        &mut self,
+        emit: &mut InstructionWriter,
+        enclosing_emitter_scope_depth: EmitterScopeDepth,
+    ) {
+        let depth = (self.control_stack.len() + 1) as u8;
+
+        let new_loop = Control::Loop(LoopControl::new(emit, depth, enclosing_emitter_scope_depth));
+
+        self.control_stack.push(new_loop);
+    }
+
+    pub fn open_label(
+        &mut self,
+        name: SourceAtomSetIndex,
+        emit: &mut InstructionWriter,
+        enclosing_emitter_scope_depth: EmitterScopeDepth,
+    ) {
+        let new_label = LabelControl::new(name, emit, enclosing_emitter_scope_depth);
+        self.control_stack.push(Control::Label(new_label));
+    }
+
+    pub fn register_break(&mut self, offset: BytecodeOffset) {
+        let innermost = self.innermost();
+
+        match innermost {
+            Control::Label(control) => control.register_break(offset),
+            Control::Loop(control) => control.register_break(offset),
+        }
+    }
+
+    pub fn register_continue(&mut self, offset: BytecodeOffset) {
+        let innermost = self.innermost();
+        match innermost {
+            Control::Label(_) => panic!(
+                "Should not register continue on a label. This should be caught by early errors."
+            ),
+            Control::Loop(control) => control.register_continue(offset),
+        }
+    }
+
+    pub fn register_labelled_break(&mut self, label: SourceAtomSetIndex, offset: BytecodeOffset) {
+        match self.find_labelled_control(label) {
+            Control::Label(control) => control.register_break(offset),
+            Control::Loop(control) => control.register_break(offset),
+        }
+    }
+
+    pub fn register_labelled_continue(
+        &mut self,
+        label: SourceAtomSetIndex,
+        offset: BytecodeOffset,
+    ) {
+        if let Some(control) = self.find_labelled_loop(label) {
+            control.register_continue(offset);
+        } else {
+            panic!(
+                "A labelled continue was passed, but no label was found. This should be caught by early errors"
+            )
+        }
+    }
+
+    pub fn find_labelled_loop(&mut self, label: SourceAtomSetIndex) -> Option<&mut LoopControl> {
+        let label_index = self.find_labelled_index(label);
+        // To find the associated loop for a label, we can take the label's index + 1, as the
+        // associated loop should always be in the position after the label.
+        let control = self.control_stack.get_mut(label_index + 1);
+        match control {
+            Some(Control::Loop(control)) => Some(control),
+            _ => None,
+        }
+    }
+
+    pub fn find_labelled_control(&mut self, label: SourceAtomSetIndex) -> &mut Control {
+        self.control_stack
+            .iter_mut()
+            .find(|control| match control {
+                Control::Label(control) => {
+                    if control.name == label {
+                        return true;
+                    }
+                    false
+                }
+                _ => false,
+            })
+            .expect("there should be a control with this label")
+    }
+
+    pub fn find_labelled_index(&mut self, label: SourceAtomSetIndex) -> usize {
+        self.control_stack
+            .iter()
+            .position(|control| match control {
+                Control::Label(control) => {
+                    if control.name == label {
+                        return true;
+                    }
+                    false
+                }
+                _ => false,
+            })
+            .expect("there should be a control with this label")
+    }
+
+    pub fn emit_continue_target_and_patch(&mut self, emit: &mut InstructionWriter) {
+        let innermost = self.innermost();
+        match innermost {
+            Control::Label(_) => panic!(
+                "Should not emit continue on a label. This should be caught by JS early errors"
+            ),
+            Control::Loop(control) => control.emit_continue_target_and_patch(emit),
+        }
+    }
+
+    fn pop_control(&mut self) -> Control {
+        self.control_stack
+            .pop()
+            .expect("There should be at least one control structure")
+    }
+
+    pub fn close_loop(&mut self, emit: &mut InstructionWriter) {
+        let mut innermost = self.pop_control();
+        match innermost {
+            Control::Label(_) => panic!("Tried to close a loop, found a label."),
+            Control::Loop(ref mut control) => {
+                control.close_loop(emit);
+                control.emit_break_target_and_patch(emit);
+            }
+        }
+    }
+
+    pub fn close_label(&mut self, emit: &mut InstructionWriter) {
+        let mut innermost = self.pop_control();
+        match innermost {
+            Control::Label(ref mut control) => control.emit_break_target_and_patch(emit),
+            Control::Loop(_) => panic!("Tried to close a label, found a loop."),
+        }
+    }
+
+    pub fn innermost(&mut self) -> &mut Control {
+        self.control_stack
+            .last_mut()
+            .expect("There should be at least one loop")
+    }
+}
+
+struct RegisteredJump<F1>
+where
+    F1: Fn(&mut AstEmitter, BytecodeOffset),
+{
+    kind: JumpKind,
+    // This callback registers the bytecode offset of the jump in a list of bytecode offsets
+    // associated with a loop or a label.
+    register_offset: F1,
+}
+
+impl<F1> Jump for RegisteredJump<F1>
+where
+    F1: Fn(&mut AstEmitter, BytecodeOffset),
+{
+    fn jump_kind(&mut self) -> &JumpKind {
+        &self.kind
+    }
+}
+
+impl<F1> RegisteredJump<F1>
+where
+    F1: Fn(&mut AstEmitter, BytecodeOffset),
+{
+    pub fn emit(&mut self, emitter: &mut AstEmitter) {
+        let offset = emitter.emit.bytecode_offset();
+        self.emit_jump(emitter);
+        (self.register_offset)(emitter, offset);
+    }
+}
+
+// Struct for multiple jumps that point to the same target. Examples are breaks and loop conditions.
+pub struct BreakEmitter {
+    pub label: Option<SourceAtomSetIndex>,
+}
+
+impl BreakEmitter {
+    pub fn emit(&mut self, emitter: &mut AstEmitter) {
+        NonLocalExitControl {
+            registered_jump: RegisteredJump {
+                kind: JumpKind::Goto,
+                register_offset: |emitter, offset| match self.label {
+                    Some(label) => emitter.control_stack.register_labelled_break(label, offset),
+                    None => emitter.control_stack.register_break(offset),
+                },
+            },
+        }
+        .emit(emitter, self.label);
+    }
+}
+
+pub struct ContinueEmitter {
+    pub label: Option<SourceAtomSetIndex>,
+}
+
+impl ContinueEmitter {
+    pub fn emit(&mut self, emitter: &mut AstEmitter) {
+        NonLocalExitControl {
+            registered_jump: RegisteredJump {
+                kind: JumpKind::Goto,
+                register_offset: |emitter, offset| match self.label {
+                    Some(label) => emitter
+                        .control_stack
+                        .register_labelled_continue(label, offset),
+                    None => emitter.control_stack.register_continue(offset),
+                },
+            },
+        }
+        .emit(emitter, self.label);
+    }
+}
+
+pub struct WhileEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub enclosing_emitter_scope_depth: EmitterScopeDepth,
+    pub test: F1,
+    pub block: F2,
+}
+impl<F1, F2> WhileEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(&mut self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        emitter
+            .control_stack
+            .open_loop(&mut emitter.emit, self.enclosing_emitter_scope_depth);
+
+        (self.test)(emitter)?;
+
+        // add a registered jump for the conditional statement
+        RegisteredJump {
+            kind: JumpKind::JumpIfFalse,
+            register_offset: |emitter, offset| emitter.control_stack.register_break(offset),
+        }
+        .emit(emitter);
+
+        (self.block)(emitter)?;
+
+        emitter
+            .control_stack
+            .emit_continue_target_and_patch(&mut emitter.emit);
+
+        // Merge point
+        emitter.control_stack.close_loop(&mut emitter.emit);
+        Ok(())
+    }
+}
+
+pub struct DoWhileEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub enclosing_emitter_scope_depth: EmitterScopeDepth,
+    pub block: F2,
+    pub test: F1,
+}
+impl<F1, F2> DoWhileEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(&mut self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        emitter
+            .control_stack
+            .open_loop(&mut emitter.emit, self.enclosing_emitter_scope_depth);
+
+        (self.block)(emitter)?;
+
+        emitter
+            .control_stack
+            .emit_continue_target_and_patch(&mut emitter.emit);
+
+        (self.test)(emitter)?;
+
+        // add a registered jump for the conditional statement
+        RegisteredJump {
+            kind: JumpKind::JumpIfFalse,
+            register_offset: |emitter, offset| emitter.control_stack.register_break(offset),
+        }
+        .emit(emitter);
+
+        // Merge point after cond fails
+        emitter.control_stack.close_loop(&mut emitter.emit);
+        Ok(())
+    }
+}
+
+pub struct CForEmitter<'a, CondT, ExprT, InitFn, TestFn, UpdateFn, BlockFn>
+where
+    InitFn: Fn(&mut AstEmitter, &CondT) -> Result<(), EmitError>,
+    TestFn: Fn(&mut AstEmitter, &ExprT) -> Result<(), EmitError>,
+    UpdateFn: Fn(&mut AstEmitter, &ExprT) -> Result<(), EmitError>,
+    BlockFn: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub enclosing_emitter_scope_depth: EmitterScopeDepth,
+    pub maybe_init: &'a Option<CondT>,
+    pub maybe_test: &'a Option<ExprT>,
+    pub maybe_update: &'a Option<ExprT>,
+    pub init: InitFn,
+    pub test: TestFn,
+    pub update: UpdateFn,
+    pub block: BlockFn,
+}
+impl<'a, CondT, ExprT, InitFn, TestFn, UpdateFn, BlockFn>
+    CForEmitter<'a, CondT, ExprT, InitFn, TestFn, UpdateFn, BlockFn>
+where
+    InitFn: Fn(&mut AstEmitter, &CondT) -> Result<(), EmitError>,
+    TestFn: Fn(&mut AstEmitter, &ExprT) -> Result<(), EmitError>,
+    UpdateFn: Fn(&mut AstEmitter, &ExprT) -> Result<(), EmitError>,
+    BlockFn: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(&mut self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        // Initialize the variable either by running an expression or assigning
+        // ie) for(foo(); <test>; <update>) or for(var x = 0; <test>; <update)
+        if let Some(init) = self.maybe_init {
+            (self.init)(emitter, init)?;
+        }
+
+        // Emit loop head
+        emitter
+            .control_stack
+            .open_loop(&mut emitter.emit, self.enclosing_emitter_scope_depth);
+
+        // if there is a test condition (ie x < 3) emit it
+        if let Some(test) = self.maybe_test {
+            (self.test)(emitter, &test)?;
+
+            // add a registered jump for the conditional statement
+            RegisteredJump {
+                kind: JumpKind::JumpIfFalse,
+                register_offset: |emitter, offset| emitter.control_stack.register_break(offset),
+            }
+            .emit(emitter);
+        }
+
+        // emit the body of the for loop.
+        (self.block)(emitter)?;
+
+        // emit the target for any continues emitted in the body before evaluating
+        // the update (if there is one) and continuing from the top of the loop.
+        emitter
+            .control_stack
+            .emit_continue_target_and_patch(&mut emitter.emit);
+
+        if let Some(update) = self.maybe_update {
+            (self.update)(emitter, &update)?;
+        }
+
+        // Merge point after test fails (or there is a break statement)
+        emitter.control_stack.close_loop(&mut emitter.emit);
+        Ok(())
+    }
+}
+
+pub struct LabelEmitter<F1>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub enclosing_emitter_scope_depth: EmitterScopeDepth,
+    pub name: SourceAtomSetIndex,
+    pub body: F1,
+}
+
+impl<F1> LabelEmitter<F1>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(&mut self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        emitter.control_stack.open_label(
+            self.name,
+            &mut emitter.emit,
+            self.enclosing_emitter_scope_depth,
+        );
+
+        (self.body)(emitter)?;
+
+        emitter.control_stack.close_label(&mut emitter.emit);
+        Ok(())
+    }
+}
+
+pub struct NonLocalExitControl<F1>
+where
+    F1: Fn(&mut AstEmitter, BytecodeOffset),
+{
+    registered_jump: RegisteredJump<F1>,
+}
+
+impl<F1> NonLocalExitControl<F1>
+where
+    F1: Fn(&mut AstEmitter, BytecodeOffset),
+{
+    pub fn emit(&mut self, emitter: &mut AstEmitter, label: Option<SourceAtomSetIndex>) {
+        // Step 1: find the enclosing emitter scope
+        let enclosing_emitter_scope_depth = match label {
+            Some(label) => emitter
+                .control_stack
+                .find_labelled_control(label)
+                .enclosing_emitter_scope_depth(),
+            None => emitter
+                .control_stack
+                .innermost()
+                .enclosing_emitter_scope_depth(),
+        };
+
+        // Step 2: find the current emitter scope
+        let mut parent_scope_note_index = emitter.scope_stack.get_current_scope_note_index();
+
+        // Step 3: iterate over scopes that have been entered since the
+        // enclosing scope, add a scope note hole for each one as we exit
+        let mut holes = Vec::new();
+        for item in emitter
+            .scope_stack
+            .walk_up_to_including(enclosing_emitter_scope_depth)
+        {
+            // We're entering `item.outer` as a scope hole of `item.inner`.
+
+            let hole_scope_note_index = match item.inner {
+                EmitterScope::Global(_) => panic!("global shouldn't be enclosed by other scope"),
+                EmitterScope::Lexical(scope) => emitter.emit.enter_scope_hole_from_lexical(
+                    &item.outer.scope_note_index(),
+                    parent_scope_note_index,
+                    scope.has_environment_object(),
+                ),
+            };
+            holes.push(hole_scope_note_index);
+            parent_scope_note_index = Some(hole_scope_note_index);
+        }
+
+        // Step 4: perform the jump
+        self.registered_jump.emit(emitter);
+
+        // Step 5: close each scope hole after the jump
+        for hole_scope_note_index in holes.iter() {
+            emitter.emit.leave_scope_hole(*hole_scope_note_index);
+        }
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/dis.rs b/third_party/rust/jsparagus-emitter/src/dis.rs
new file mode 100644
index 0000000000..f9978b8d9c
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/dis.rs
@@ -0,0 +1,34 @@
+use std::convert::TryFrom;
+use std::fmt::Write;
+use stencil::opcode::Opcode;
+
+/// Return a string form of the given bytecode.
+pub fn dis(bc: &[u8]) -> String {
+    let mut result = String::new();
+    let mut iter = bc.iter();
+    let mut offset = 0;
+    loop {
+        let len = match iter.next() {
+            Some(byte) => match Opcode::try_from(*byte) {
+                Ok(op) => {
+                    write!(&mut result, "{}", format!("{:05}: {:?}", offset, op)).unwrap();
+                    offset = offset + op.instruction_length();
+                    op.instruction_length()
+                }
+                Err(()) => {
+                    write!(&mut result, "{}", byte).unwrap();
+                    1
+                }
+            },
+            None => break,
+        };
+
+        for _ in 1..len {
+            write!(&mut result, " {}", iter.next().unwrap()).unwrap();
+        }
+
+        writeln!(&mut result).unwrap();
+    }
+
+    result
+}
diff --git a/third_party/rust/jsparagus-emitter/src/emitter.rs b/third_party/rust/jsparagus-emitter/src/emitter.rs
new file mode 100644
index 0000000000..1bcefab1ae
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/emitter.rs
@@ -0,0 +1,1461 @@
+//! Low-level bytecode emitter, used by ast_builder.
+//!
+//! This API makes it easy to emit correct individual bytecode instructions.
+
+// Most of this functionality isn't used yet.
+#![allow(dead_code)]
+
+use ast::source_atom_set::SourceAtomSetIndex;
+use byteorder::{ByteOrder, LittleEndian};
+use std::cmp;
+use std::collections::HashMap;
+use std::convert::TryFrom;
+use std::convert::TryInto;
+use std::fmt;
+use stencil::bytecode_offset::{BytecodeOffset, BytecodeOffsetDiff};
+use stencil::frame_slot::FrameSlot;
+use stencil::gcthings::{GCThingIndex, GCThingList};
+use stencil::opcode::Opcode;
+use stencil::regexp::RegExpIndex;
+use stencil::scope::ScopeIndex;
+use stencil::scope_notes::{ScopeNoteIndex, ScopeNoteList};
+use stencil::script::{
+    ImmutableScriptData, ImmutableScriptDataList, ScriptStencil, ScriptStencilIndex, SourceExtent,
+};
+
+// WARNING
+// The following section is generated by update_stencil.py.
+// Do mot modify manually.
+//
+// @@@@ BEGIN TYPES @@@@
+#[derive(Debug, Clone, Copy)]
+pub enum AsyncFunctionResolveKind {
+    Fulfill = 0,
+    Reject = 1,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum CheckIsObjectKind {
+    IteratorNext = 0,
+    IteratorReturn = 1,
+    IteratorThrow = 2,
+    GetIterator = 3,
+    GetAsyncIterator = 4,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum CompletionKind {
+    Normal = 0,
+    Return = 1,
+    Throw = 2,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum FunctionPrefixKind {
+    None = 0,
+    Get = 1,
+    Set = 2,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum GeneratorResumeKind {
+    Next = 0,
+    Throw = 1,
+    Return = 2,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum ThrowMsgKind {
+    AssignToCall = 0,
+    IteratorNoThrow = 1,
+    CantDeleteSuper = 2,
+    PrivateDoubleInit = 3,
+    PrivateBrandDoubleInit = 4,
+    MissingPrivateOnGet = 5,
+    MissingPrivateOnSet = 6,
+    AssignToPrivateMethod = 7,
+    DecoratorInvalidReturnType = 8,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum ThrowCondition {
+    ThrowHas = 0,
+    ThrowHasNot = 1,
+    OnlyCheckRhs = 2,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum TryNoteKind {
+    Catch = 0,
+    Finally = 1,
+    ForIn = 2,
+    Destructuring = 3,
+    ForOf = 4,
+    ForOfIterClose = 5,
+    Loop = 6,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum SymbolCode {
+    IsConcatSpreadable = 0,
+    Iterator = 1,
+    Match = 2,
+    Replace = 3,
+    Search = 4,
+    Species = 5,
+    HasInstance = 6,
+    Split = 7,
+    ToPrimitive = 8,
+    ToStringTag = 9,
+    Unscopables = 10,
+    AsyncIterator = 11,
+    MatchAll = 12,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum SrcNoteType {
+    Null = 0,
+    AssignOp = 1,
+    ColSpan = 2,
+    NewLine = 3,
+    SetLine = 4,
+    Breakpoint = 5,
+    StepSep = 6,
+    Unused7 = 7,
+    XDelta = 8,
+}
+
+// @@@@ END TYPES @@@@
+
+#[allow(non_camel_case_types)]
+pub type u24 = u32;
+
+/// Low-level bytecode emitter.
+pub struct InstructionWriter {
+    bytecode: Vec<u8>,
+
+    /// To de-duplicate atoms in gcthings list, note the index for each atom.
+    atom_to_gcindex_map: HashMap<SourceAtomSetIndex, GCThingIndex>,
+
+    gcthings: GCThingList,
+    scope_notes: ScopeNoteList,
+
+    last_jump_target_offset: Option<BytecodeOffset>,
+
+    main_offset: BytecodeOffset,
+
+    /// The maximum number of fixed frame slots.
+    max_fixed_slots: FrameSlot,
+
+    /// Stack depth after the instructions emitted so far.
+    stack_depth: usize,
+
+    /// Maximum stack_depth at any point in the instructions emitted so far.
+    maximum_stack_depth: usize,
+
+    body_scope_index: Option<GCThingIndex>,
+
+    /// Number of JOF_IC instructions emitted so far.
+    num_ic_entries: usize,
+}
+
+#[derive(Debug)]
+pub struct EmitOptions {
+    pub no_script_rval: bool,
+    pub extent: SourceExtent,
+}
+impl EmitOptions {
+    pub fn new(extent: SourceExtent) -> Self {
+        Self {
+            no_script_rval: false,
+            extent,
+        }
+    }
+}
+
+/// The error of bytecode-compilation.
+#[derive(Clone, Debug)]
+pub enum EmitError {
+    NotImplemented(&'static str),
+}
+
+impl fmt::Display for EmitError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            EmitError::NotImplemented(message) => write!(f, "not implemented: {}", message),
+        }
+    }
+}
+
+impl InstructionWriter {
+    pub fn new() -> Self {
+        Self {
+            bytecode: Vec::new(),
+            gcthings: GCThingList::new(),
+            atom_to_gcindex_map: HashMap::new(),
+            scope_notes: ScopeNoteList::new(),
+            last_jump_target_offset: None,
+            main_offset: BytecodeOffset::from(0usize),
+            max_fixed_slots: FrameSlot::new(0),
+            stack_depth: 0,
+            maximum_stack_depth: 0,
+            body_scope_index: None,
+            num_ic_entries: 0,
+        }
+    }
+
+    fn write_i8(&mut self, value: i8) {
+        self.write_u8(value as u8);
+    }
+
+    fn write_u8(&mut self, value: u8) {
+        self.bytecode.push(value);
+    }
+
+    fn write_u16(&mut self, value: u16) {
+        self.bytecode.extend_from_slice(&value.to_le_bytes());
+    }
+
+    fn write_u24(&mut self, value: u24) {
+        let slice = value.to_le_bytes();
+        assert!(slice.len() == 4 && slice[3] == 0);
+        self.bytecode.extend_from_slice(&slice[0..3]);
+    }
+
+    fn write_i32(&mut self, value: i32) {
+        self.bytecode.extend_from_slice(&value.to_le_bytes());
+    }
+
+    fn write_u32(&mut self, value: u32) {
+        self.bytecode.extend_from_slice(&value.to_le_bytes());
+    }
+
+    fn write_g_c_thing_index(&mut self, value: GCThingIndex) {
+        self.write_u32(usize::from(value) as u32);
+    }
+
+    fn write_offset(&mut self, offset: i32) {
+        self.write_i32(offset);
+    }
+
+    fn write_bytecode_offset_diff(&mut self, offset: BytecodeOffsetDiff) {
+        self.write_i32(i32::from(offset));
+    }
+
+    fn write_f64(&mut self, val: f64) {
+        self.bytecode
+            .extend_from_slice(&val.to_bits().to_le_bytes());
+    }
+
+    fn write_ic_index(&mut self) {
+        self.write_u32(self.num_ic_entries.try_into().unwrap());
+    }
+
+    fn emit_op(&mut self, opcode: Opcode) {
+        let nuses: isize = opcode.nuses();
+        assert!(nuses >= 0);
+        self.emit_op_common(opcode, nuses as usize);
+    }
+
+    fn emit_argc_op(&mut self, opcode: Opcode, argc: u16) {
+        assert!(opcode.has_argc());
+        assert_eq!(opcode.nuses(), -1);
+        let nuses = match opcode {
+            Opcode::Call
+            | Opcode::CallIgnoresRv
+            | Opcode::Eval
+            | Opcode::CallIter
+            | Opcode::StrictEval => {
+                // callee, this, arguments...
+                2 + (argc as usize)
+            }
+
+            Opcode::New | Opcode::SuperCall => {
+                // callee, isConstructing, arguments..., newtarget
+                2 + (argc as usize) + 1
+            }
+
+            _ => panic!("Unsupported opcode"),
+        };
+        self.emit_op_common(opcode, nuses);
+    }
+
+    fn emit_pop_n_op(&mut self, opcode: Opcode, n: u16) {
+        assert_eq!(opcode.nuses(), -1);
+        debug_assert_eq!(opcode, Opcode::PopN);
+        self.emit_op_common(opcode, n as usize);
+    }
+
+    fn emit_op_common(&mut self, opcode: Opcode, nuses: usize) {
+        assert!(
+            self.stack_depth >= nuses as usize,
+            "InstructionWriter misuse! Not enough arguments on the stack."
+        );
+        self.stack_depth -= nuses as usize;
+
+        let ndefs = opcode.ndefs();
+        if ndefs > 0 {
+            self.stack_depth += ndefs;
+            if self.stack_depth > self.maximum_stack_depth {
+                self.maximum_stack_depth = self.stack_depth;
+            }
+        }
+
+        if opcode.has_ic_entry() {
+            self.num_ic_entries += 1;
+        }
+
+        self.bytecode.push(opcode.to_byte());
+    }
+
+    fn set_last_jump_target_offset(&mut self, target: BytecodeOffset) {
+        self.last_jump_target_offset = Some(target);
+    }
+
+    fn get_end_of_bytecode(&mut self, offset: BytecodeOffset) -> usize {
+        // find the offset after the end of bytecode associated with this offset.
+        let target_opcode = Opcode::try_from(self.bytecode[offset.offset]).unwrap();
+        offset.offset + target_opcode.instruction_length()
+    }
+
+    pub fn emit_jump_target_and_patch(&mut self, jumplist: &Vec<BytecodeOffset>) {
+        let mut target = self.bytecode_offset();
+        let last_jump = self.last_jump_target_offset;
+        match last_jump {
+            Some(offset) => {
+                if self.get_end_of_bytecode(offset) != target.offset {
+                    self.jump_target();
+                    self.set_last_jump_target_offset(target);
+                } else {
+                    target = offset;
+                }
+            }
+            None => {
+                self.jump_target();
+                self.set_last_jump_target_offset(target);
+            }
+        }
+
+        for jump in jumplist {
+            self.patch_jump_to_target(target, *jump);
+        }
+    }
+
+    pub fn patch_jump_to_target(&mut self, target: BytecodeOffset, jump: BytecodeOffset) {
+        let diff = target.diff_from(jump).into();
+        let index = jump.offset + 1;
+        // FIXME: Use native endian instead of little endian
+        LittleEndian::write_i32(&mut self.bytecode[index..index + 4], diff);
+    }
+
+    pub fn bytecode_offset(&mut self) -> BytecodeOffset {
+        BytecodeOffset::from(self.bytecode.len())
+    }
+
+    pub fn stack_depth(&self) -> usize {
+        self.stack_depth
+    }
+
+    pub fn set_stack_depth(&mut self, depth: usize) {
+        self.stack_depth = depth;
+    }
+
+    // Public methods to emit each instruction.
+
+    pub fn emit_boolean(&mut self, value: bool) {
+        self.emit_op(if value { Opcode::True } else { Opcode::False });
+    }
+
+    pub fn emit_unary_op(&mut self, opcode: Opcode) {
+        assert!(opcode.is_simple_unary_operator());
+        self.emit_op(opcode);
+    }
+
+    pub fn emit_binary_op(&mut self, opcode: Opcode) {
+        assert!(opcode.is_simple_binary_operator());
+        debug_assert_eq!(opcode.nuses(), 2);
+        debug_assert_eq!(opcode.ndefs(), 1);
+        self.emit_op(opcode);
+    }
+
+    pub fn table_switch(
+        &mut self,
+        _len: i32,
+        _low: i32,
+        _high: i32,
+        _first_resume_index: u24,
+    ) -> Result<(), EmitError> {
+        Err(EmitError::NotImplemented("TODO: table_switch"))
+    }
+
+    pub fn numeric(&mut self, value: f64) {
+        if value.is_finite() && value.fract() == 0.0 {
+            if i8::min_value() as f64 <= value && value <= i8::max_value() as f64 {
+                match value as i8 {
+                    0 => self.zero(),
+                    1 => self.one(),
+                    i => self.int8(i),
+                }
+                return;
+            }
+            if 0.0 <= value {
+                if value <= u16::max_value() as f64 {
+                    self.uint16(value as u16);
+                    return;
+                }
+                if value <= 0x00ffffff as f64 {
+                    self.uint24(value as u24);
+                    return;
+                }
+            }
+            if i32::min_value() as f64 <= value && value <= i32::max_value() as f64 {
+                self.int32(value as i32);
+                return;
+            }
+        }
+        self.double_(value);
+    }
+
+    // WARNING
+    // The following section is generated by update_stencil.py.
+    // Do mot modify manually.
+    //
+    // @@@@ BEGIN METHODS @@@@
+    pub fn undefined(&mut self) {
+        self.emit_op(Opcode::Undefined);
+    }
+
+    pub fn null(&mut self) {
+        self.emit_op(Opcode::Null);
+    }
+
+    pub fn int32(&mut self, val: i32) {
+        self.emit_op(Opcode::Int32);
+        self.write_i32(val);
+    }
+
+    pub fn zero(&mut self) {
+        self.emit_op(Opcode::Zero);
+    }
+
+    pub fn one(&mut self) {
+        self.emit_op(Opcode::One);
+    }
+
+    pub fn int8(&mut self, val: i8) {
+        self.emit_op(Opcode::Int8);
+        self.write_i8(val);
+    }
+
+    pub fn uint16(&mut self, val: u16) {
+        self.emit_op(Opcode::Uint16);
+        self.write_u16(val);
+    }
+
+    pub fn uint24(&mut self, val: u24) {
+        self.emit_op(Opcode::Uint24);
+        self.write_u24(val);
+    }
+
+    pub fn double_(&mut self, val: f64) {
+        self.emit_op(Opcode::Double);
+        self.write_f64(val);
+    }
+
+    pub fn big_int(&mut self, big_int_index: u32) {
+        self.emit_op(Opcode::BigInt);
+        self.write_u32(big_int_index);
+    }
+
+    pub fn string(&mut self, atom_index: GCThingIndex) {
+        self.emit_op(Opcode::String);
+        self.write_g_c_thing_index(atom_index);
+    }
+
+    pub fn symbol(&mut self, symbol: u8) {
+        self.emit_op(Opcode::Symbol);
+        self.write_u8(symbol);
+    }
+
+    pub fn typeof_(&mut self) {
+        self.emit_op(Opcode::Typeof);
+    }
+
+    pub fn typeof_expr(&mut self) {
+        self.emit_op(Opcode::TypeofExpr);
+    }
+
+    pub fn inc(&mut self) {
+        self.emit_op(Opcode::Inc);
+    }
+
+    pub fn dec(&mut self) {
+        self.emit_op(Opcode::Dec);
+    }
+
+    pub fn to_property_key(&mut self) {
+        self.emit_op(Opcode::ToPropertyKey);
+    }
+
+    pub fn to_numeric(&mut self) {
+        self.emit_op(Opcode::ToNumeric);
+    }
+
+    pub fn to_string(&mut self) {
+        self.emit_op(Opcode::ToString);
+    }
+
+    pub fn is_null_or_undefined(&mut self) {
+        self.emit_op(Opcode::IsNullOrUndefined);
+    }
+
+    pub fn global_this(&mut self) {
+        self.emit_op(Opcode::GlobalThis);
+    }
+
+    pub fn non_syntactic_global_this(&mut self) {
+        self.emit_op(Opcode::NonSyntacticGlobalThis);
+    }
+
+    pub fn new_target(&mut self) {
+        self.emit_op(Opcode::NewTarget);
+    }
+
+    pub fn dynamic_import(&mut self) {
+        self.emit_op(Opcode::DynamicImport);
+    }
+
+    pub fn import_meta(&mut self) {
+        self.emit_op(Opcode::ImportMeta);
+    }
+
+    pub fn new_init(&mut self) {
+        self.emit_op(Opcode::NewInit);
+    }
+
+    pub fn new_object(&mut self, shape_index: GCThingIndex) {
+        self.emit_op(Opcode::NewObject);
+        self.write_g_c_thing_index(shape_index);
+    }
+
+    pub fn object(&mut self, object_index: GCThingIndex) {
+        self.emit_op(Opcode::Object);
+        self.write_g_c_thing_index(object_index);
+    }
+
+    pub fn obj_with_proto(&mut self) {
+        self.emit_op(Opcode::ObjWithProto);
+    }
+
+    pub fn init_prop(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::InitProp);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn init_hidden_prop(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::InitHiddenProp);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn init_locked_prop(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::InitLockedProp);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn init_elem(&mut self) {
+        self.emit_op(Opcode::InitElem);
+    }
+
+    pub fn init_hidden_elem(&mut self) {
+        self.emit_op(Opcode::InitHiddenElem);
+    }
+
+    pub fn init_locked_elem(&mut self) {
+        self.emit_op(Opcode::InitLockedElem);
+    }
+
+    pub fn init_prop_getter(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::InitPropGetter);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn init_hidden_prop_getter(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::InitHiddenPropGetter);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn init_elem_getter(&mut self) {
+        self.emit_op(Opcode::InitElemGetter);
+    }
+
+    pub fn init_hidden_elem_getter(&mut self) {
+        self.emit_op(Opcode::InitHiddenElemGetter);
+    }
+
+    pub fn init_prop_setter(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::InitPropSetter);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn init_hidden_prop_setter(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::InitHiddenPropSetter);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn init_elem_setter(&mut self) {
+        self.emit_op(Opcode::InitElemSetter);
+    }
+
+    pub fn init_hidden_elem_setter(&mut self) {
+        self.emit_op(Opcode::InitHiddenElemSetter);
+    }
+
+    pub fn get_prop(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::GetProp);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn get_elem(&mut self) {
+        self.emit_op(Opcode::GetElem);
+    }
+
+    pub fn set_prop(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::SetProp);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn strict_set_prop(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::StrictSetProp);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn set_elem(&mut self) {
+        self.emit_op(Opcode::SetElem);
+    }
+
+    pub fn strict_set_elem(&mut self) {
+        self.emit_op(Opcode::StrictSetElem);
+    }
+
+    pub fn del_prop(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::DelProp);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn strict_del_prop(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::StrictDelProp);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn del_elem(&mut self) {
+        self.emit_op(Opcode::DelElem);
+    }
+
+    pub fn strict_del_elem(&mut self) {
+        self.emit_op(Opcode::StrictDelElem);
+    }
+
+    pub fn has_own(&mut self) {
+        self.emit_op(Opcode::HasOwn);
+    }
+
+    pub fn check_private_field(&mut self, throw_condition: ThrowCondition, msg_kind: ThrowMsgKind) {
+        self.emit_op(Opcode::CheckPrivateField);
+        self.write_u8(throw_condition as u8);
+        self.write_u8(msg_kind as u8);
+    }
+
+    pub fn new_private_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::NewPrivateName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn super_base(&mut self) {
+        self.emit_op(Opcode::SuperBase);
+    }
+
+    pub fn get_prop_super(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::GetPropSuper);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn get_elem_super(&mut self) {
+        self.emit_op(Opcode::GetElemSuper);
+    }
+
+    pub fn set_prop_super(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::SetPropSuper);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn strict_set_prop_super(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::StrictSetPropSuper);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn set_elem_super(&mut self) {
+        self.emit_op(Opcode::SetElemSuper);
+    }
+
+    pub fn strict_set_elem_super(&mut self) {
+        self.emit_op(Opcode::StrictSetElemSuper);
+    }
+
+    pub fn iter(&mut self) {
+        self.emit_op(Opcode::Iter);
+    }
+
+    pub fn more_iter(&mut self) {
+        self.emit_op(Opcode::MoreIter);
+    }
+
+    pub fn is_no_iter(&mut self) {
+        self.emit_op(Opcode::IsNoIter);
+    }
+
+    pub fn end_iter(&mut self) {
+        self.emit_op(Opcode::EndIter);
+    }
+
+    pub fn close_iter(&mut self, kind: CompletionKind) {
+        self.emit_op(Opcode::CloseIter);
+        self.write_u8(kind as u8);
+    }
+
+    pub fn check_is_obj(&mut self, kind: CheckIsObjectKind) {
+        self.emit_op(Opcode::CheckIsObj);
+        self.write_u8(kind as u8);
+    }
+
+    pub fn check_obj_coercible(&mut self) {
+        self.emit_op(Opcode::CheckObjCoercible);
+    }
+
+    pub fn to_async_iter(&mut self) {
+        self.emit_op(Opcode::ToAsyncIter);
+    }
+
+    pub fn mutate_proto(&mut self) {
+        self.emit_op(Opcode::MutateProto);
+    }
+
+    pub fn new_array(&mut self, length: u32) {
+        self.emit_op(Opcode::NewArray);
+        self.write_u32(length);
+    }
+
+    pub fn init_elem_array(&mut self, index: u32) {
+        self.emit_op(Opcode::InitElemArray);
+        self.write_u32(index);
+    }
+
+    pub fn init_elem_inc(&mut self) {
+        self.emit_op(Opcode::InitElemInc);
+    }
+
+    pub fn hole(&mut self) {
+        self.emit_op(Opcode::Hole);
+    }
+
+    pub fn reg_exp(&mut self, regexp_index: GCThingIndex) {
+        self.emit_op(Opcode::RegExp);
+        self.write_g_c_thing_index(regexp_index);
+    }
+
+    pub fn lambda(&mut self, func_index: GCThingIndex) {
+        self.emit_op(Opcode::Lambda);
+        self.write_g_c_thing_index(func_index);
+    }
+
+    pub fn set_fun_name(&mut self, prefix_kind: FunctionPrefixKind) {
+        self.emit_op(Opcode::SetFunName);
+        self.write_u8(prefix_kind as u8);
+    }
+
+    pub fn init_home_object(&mut self) {
+        self.emit_op(Opcode::InitHomeObject);
+    }
+
+    pub fn check_class_heritage(&mut self) {
+        self.emit_op(Opcode::CheckClassHeritage);
+    }
+
+    pub fn fun_with_proto(&mut self, func_index: GCThingIndex) {
+        self.emit_op(Opcode::FunWithProto);
+        self.write_g_c_thing_index(func_index);
+    }
+
+    pub fn builtin_object(&mut self, kind: u8) {
+        self.emit_op(Opcode::BuiltinObject);
+        self.write_u8(kind);
+    }
+
+    pub fn call(&mut self, argc: u16) {
+        self.emit_argc_op(Opcode::Call, argc);
+        self.write_u16(argc);
+    }
+
+    pub fn call_content(&mut self, argc: u16) {
+        self.emit_argc_op(Opcode::CallContent, argc);
+        self.write_u16(argc);
+    }
+
+    pub fn call_iter(&mut self, argc: u16) {
+        self.emit_argc_op(Opcode::CallIter, argc);
+        self.write_u16(argc);
+    }
+
+    pub fn call_content_iter(&mut self, argc: u16) {
+        self.emit_argc_op(Opcode::CallContentIter, argc);
+        self.write_u16(argc);
+    }
+
+    pub fn call_ignores_rv(&mut self, argc: u16) {
+        self.emit_argc_op(Opcode::CallIgnoresRv, argc);
+        self.write_u16(argc);
+    }
+
+    pub fn spread_call(&mut self) {
+        self.emit_op(Opcode::SpreadCall);
+    }
+
+    pub fn optimize_spread_call(&mut self) {
+        self.emit_op(Opcode::OptimizeSpreadCall);
+    }
+
+    pub fn eval(&mut self, argc: u16) {
+        self.emit_argc_op(Opcode::Eval, argc);
+        self.write_u16(argc);
+    }
+
+    pub fn spread_eval(&mut self) {
+        self.emit_op(Opcode::SpreadEval);
+    }
+
+    pub fn strict_eval(&mut self, argc: u16) {
+        self.emit_argc_op(Opcode::StrictEval, argc);
+        self.write_u16(argc);
+    }
+
+    pub fn strict_spread_eval(&mut self) {
+        self.emit_op(Opcode::StrictSpreadEval);
+    }
+
+    pub fn implicit_this(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::ImplicitThis);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn call_site_obj(&mut self, object_index: GCThingIndex) {
+        self.emit_op(Opcode::CallSiteObj);
+        self.write_g_c_thing_index(object_index);
+    }
+
+    pub fn is_constructing(&mut self) {
+        self.emit_op(Opcode::IsConstructing);
+    }
+
+    pub fn new_(&mut self, argc: u16) {
+        self.emit_argc_op(Opcode::New, argc);
+        self.write_u16(argc);
+    }
+
+    pub fn new_content(&mut self, argc: u16) {
+        self.emit_argc_op(Opcode::NewContent, argc);
+        self.write_u16(argc);
+    }
+
+    pub fn super_call(&mut self, argc: u16) {
+        self.emit_argc_op(Opcode::SuperCall, argc);
+        self.write_u16(argc);
+    }
+
+    pub fn spread_new(&mut self) {
+        self.emit_op(Opcode::SpreadNew);
+    }
+
+    pub fn spread_super_call(&mut self) {
+        self.emit_op(Opcode::SpreadSuperCall);
+    }
+
+    pub fn super_fun(&mut self) {
+        self.emit_op(Opcode::SuperFun);
+    }
+
+    pub fn check_this_reinit(&mut self) {
+        self.emit_op(Opcode::CheckThisReinit);
+    }
+
+    pub fn generator(&mut self) {
+        self.emit_op(Opcode::Generator);
+    }
+
+    pub fn initial_yield(&mut self, resume_index: u24) {
+        self.emit_op(Opcode::InitialYield);
+        self.write_u24(resume_index);
+    }
+
+    pub fn after_yield(&mut self) {
+        self.emit_op(Opcode::AfterYield);
+        self.write_ic_index();
+    }
+
+    pub fn final_yield_rval(&mut self) {
+        self.emit_op(Opcode::FinalYieldRval);
+    }
+
+    pub fn yield_(&mut self, resume_index: u24) {
+        self.emit_op(Opcode::Yield);
+        self.write_u24(resume_index);
+    }
+
+    pub fn is_gen_closing(&mut self) {
+        self.emit_op(Opcode::IsGenClosing);
+    }
+
+    pub fn async_await(&mut self) {
+        self.emit_op(Opcode::AsyncAwait);
+    }
+
+    pub fn async_resolve(&mut self, fulfill_or_reject: AsyncFunctionResolveKind) {
+        self.emit_op(Opcode::AsyncResolve);
+        self.write_u8(fulfill_or_reject as u8);
+    }
+
+    pub fn await_(&mut self, resume_index: u24) {
+        self.emit_op(Opcode::Await);
+        self.write_u24(resume_index);
+    }
+
+    pub fn can_skip_await(&mut self) {
+        self.emit_op(Opcode::CanSkipAwait);
+    }
+
+    pub fn maybe_extract_await_value(&mut self) {
+        self.emit_op(Opcode::MaybeExtractAwaitValue);
+    }
+
+    pub fn resume_kind(&mut self, resume_kind: GeneratorResumeKind) {
+        self.emit_op(Opcode::ResumeKind);
+        self.write_u8(resume_kind as u8);
+    }
+
+    pub fn check_resume_kind(&mut self) {
+        self.emit_op(Opcode::CheckResumeKind);
+    }
+
+    pub fn resume(&mut self) {
+        self.emit_op(Opcode::Resume);
+    }
+
+    pub fn jump_target(&mut self) {
+        self.emit_op(Opcode::JumpTarget);
+        self.write_ic_index();
+    }
+
+    pub fn loop_head(&mut self, depth_hint: u8) {
+        self.emit_op(Opcode::LoopHead);
+        self.write_ic_index();
+        self.write_u8(depth_hint);
+    }
+
+    pub fn goto_(&mut self, offset: BytecodeOffsetDiff) {
+        self.emit_op(Opcode::Goto);
+        self.write_bytecode_offset_diff(offset);
+    }
+
+    pub fn jump_if_false(&mut self, forward_offset: BytecodeOffsetDiff) {
+        self.emit_op(Opcode::JumpIfFalse);
+        self.write_bytecode_offset_diff(forward_offset);
+    }
+
+    pub fn jump_if_true(&mut self, offset: BytecodeOffsetDiff) {
+        self.emit_op(Opcode::JumpIfTrue);
+        self.write_bytecode_offset_diff(offset);
+    }
+
+    pub fn and_(&mut self, forward_offset: BytecodeOffsetDiff) {
+        self.emit_op(Opcode::And);
+        self.write_bytecode_offset_diff(forward_offset);
+    }
+
+    pub fn or_(&mut self, forward_offset: BytecodeOffsetDiff) {
+        self.emit_op(Opcode::Or);
+        self.write_bytecode_offset_diff(forward_offset);
+    }
+
+    pub fn coalesce(&mut self, forward_offset: BytecodeOffsetDiff) {
+        self.emit_op(Opcode::Coalesce);
+        self.write_bytecode_offset_diff(forward_offset);
+    }
+
+    pub fn case_(&mut self, forward_offset: BytecodeOffsetDiff) {
+        self.emit_op(Opcode::Case);
+        self.write_bytecode_offset_diff(forward_offset);
+    }
+
+    pub fn default_(&mut self, forward_offset: BytecodeOffsetDiff) {
+        self.emit_op(Opcode::Default);
+        self.write_bytecode_offset_diff(forward_offset);
+    }
+
+    pub fn return_(&mut self) {
+        self.emit_op(Opcode::Return);
+    }
+
+    pub fn get_rval(&mut self) {
+        self.emit_op(Opcode::GetRval);
+    }
+
+    pub fn set_rval(&mut self) {
+        self.emit_op(Opcode::SetRval);
+    }
+
+    pub fn ret_rval(&mut self) {
+        self.emit_op(Opcode::RetRval);
+    }
+
+    pub fn check_return(&mut self) {
+        self.emit_op(Opcode::CheckReturn);
+    }
+
+    pub fn throw_(&mut self) {
+        self.emit_op(Opcode::Throw);
+    }
+
+    pub fn throw_msg(&mut self, msg_number: ThrowMsgKind) {
+        self.emit_op(Opcode::ThrowMsg);
+        self.write_u8(msg_number as u8);
+    }
+
+    pub fn throw_set_const(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::ThrowSetConst);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn try_(&mut self) {
+        self.emit_op(Opcode::Try);
+    }
+
+    pub fn try_destructuring(&mut self) {
+        self.emit_op(Opcode::TryDestructuring);
+    }
+
+    pub fn exception(&mut self) {
+        self.emit_op(Opcode::Exception);
+    }
+
+    pub fn finally(&mut self) {
+        self.emit_op(Opcode::Finally);
+    }
+
+    pub fn uninitialized(&mut self) {
+        self.emit_op(Opcode::Uninitialized);
+    }
+
+    pub fn init_lexical(&mut self, localno: u24) {
+        self.emit_op(Opcode::InitLexical);
+        self.write_u24(localno);
+    }
+
+    pub fn init_g_lexical(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::InitGLexical);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn init_aliased_lexical(&mut self, hops: u8, slot: u24) {
+        self.emit_op(Opcode::InitAliasedLexical);
+        self.write_u8(hops);
+        self.write_u24(slot);
+    }
+
+    pub fn check_lexical(&mut self, localno: u24) {
+        self.emit_op(Opcode::CheckLexical);
+        self.write_u24(localno);
+    }
+
+    pub fn check_aliased_lexical(&mut self, hops: u8, slot: u24) {
+        self.emit_op(Opcode::CheckAliasedLexical);
+        self.write_u8(hops);
+        self.write_u24(slot);
+    }
+
+    pub fn check_this(&mut self) {
+        self.emit_op(Opcode::CheckThis);
+    }
+
+    pub fn bind_g_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::BindGName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn bind_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::BindName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn get_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::GetName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn get_g_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::GetGName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn get_arg(&mut self, argno: u16) {
+        self.emit_op(Opcode::GetArg);
+        self.write_u16(argno);
+    }
+
+    pub fn get_local(&mut self, localno: u24) {
+        self.emit_op(Opcode::GetLocal);
+        self.write_u24(localno);
+    }
+
+    pub fn get_aliased_var(&mut self, hops: u8, slot: u24) {
+        self.emit_op(Opcode::GetAliasedVar);
+        self.write_u8(hops);
+        self.write_u24(slot);
+    }
+
+    pub fn get_aliased_debug_var(&mut self, hops: u8, slot: u24) {
+        self.emit_op(Opcode::GetAliasedDebugVar);
+        self.write_u8(hops);
+        self.write_u24(slot);
+    }
+
+    pub fn get_import(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::GetImport);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn get_bound_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::GetBoundName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn get_intrinsic(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::GetIntrinsic);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn callee(&mut self) {
+        self.emit_op(Opcode::Callee);
+    }
+
+    pub fn env_callee(&mut self, num_hops: u8) {
+        self.emit_op(Opcode::EnvCallee);
+        self.write_u8(num_hops);
+    }
+
+    pub fn set_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::SetName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn strict_set_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::StrictSetName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn set_g_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::SetGName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn strict_set_g_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::StrictSetGName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn set_arg(&mut self, argno: u16) {
+        self.emit_op(Opcode::SetArg);
+        self.write_u16(argno);
+    }
+
+    pub fn set_local(&mut self, localno: u24) {
+        self.emit_op(Opcode::SetLocal);
+        self.write_u24(localno);
+    }
+
+    pub fn set_aliased_var(&mut self, hops: u8, slot: u24) {
+        self.emit_op(Opcode::SetAliasedVar);
+        self.write_u8(hops);
+        self.write_u24(slot);
+    }
+
+    pub fn set_intrinsic(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::SetIntrinsic);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn push_lexical_env(&mut self, lexical_scope_index: GCThingIndex) {
+        self.emit_op(Opcode::PushLexicalEnv);
+        self.write_g_c_thing_index(lexical_scope_index);
+    }
+
+    pub fn pop_lexical_env(&mut self) {
+        self.emit_op(Opcode::PopLexicalEnv);
+    }
+
+    pub fn debug_leave_lexical_env(&mut self) {
+        self.emit_op(Opcode::DebugLeaveLexicalEnv);
+    }
+
+    pub fn recreate_lexical_env(&mut self, lexical_scope_index: GCThingIndex) {
+        self.emit_op(Opcode::RecreateLexicalEnv);
+        self.write_g_c_thing_index(lexical_scope_index);
+    }
+
+    pub fn freshen_lexical_env(&mut self, lexical_scope_index: GCThingIndex) {
+        self.emit_op(Opcode::FreshenLexicalEnv);
+        self.write_g_c_thing_index(lexical_scope_index);
+    }
+
+    pub fn push_class_body_env(&mut self, lexical_scope_index: GCThingIndex) {
+        self.emit_op(Opcode::PushClassBodyEnv);
+        self.write_g_c_thing_index(lexical_scope_index);
+    }
+
+    pub fn push_var_env(&mut self, scope_index: GCThingIndex) {
+        self.emit_op(Opcode::PushVarEnv);
+        self.write_g_c_thing_index(scope_index);
+    }
+
+    pub fn enter_with(&mut self, static_with_index: GCThingIndex) {
+        self.emit_op(Opcode::EnterWith);
+        self.write_g_c_thing_index(static_with_index);
+    }
+
+    pub fn leave_with(&mut self) {
+        self.emit_op(Opcode::LeaveWith);
+    }
+
+    pub fn bind_var(&mut self) {
+        self.emit_op(Opcode::BindVar);
+    }
+
+    pub fn global_or_eval_decl_instantiation(&mut self, last_fun: u32) {
+        self.emit_op(Opcode::GlobalOrEvalDeclInstantiation);
+        self.write_u32(last_fun);
+    }
+
+    pub fn del_name(&mut self, name_index: GCThingIndex) {
+        self.emit_op(Opcode::DelName);
+        self.write_g_c_thing_index(name_index);
+    }
+
+    pub fn arguments(&mut self) {
+        self.emit_op(Opcode::Arguments);
+    }
+
+    pub fn rest(&mut self) {
+        self.emit_op(Opcode::Rest);
+    }
+
+    pub fn function_this(&mut self) {
+        self.emit_op(Opcode::FunctionThis);
+    }
+
+    pub fn pop(&mut self) {
+        self.emit_op(Opcode::Pop);
+    }
+
+    pub fn pop_n(&mut self, n: u16) {
+        self.emit_pop_n_op(Opcode::PopN, n);
+        self.write_u16(n);
+    }
+
+    pub fn dup(&mut self) {
+        self.emit_op(Opcode::Dup);
+    }
+
+    pub fn dup2(&mut self) {
+        self.emit_op(Opcode::Dup2);
+    }
+
+    pub fn dup_at(&mut self, n: u24) {
+        self.emit_op(Opcode::DupAt);
+        self.write_u24(n);
+    }
+
+    pub fn swap(&mut self) {
+        self.emit_op(Opcode::Swap);
+    }
+
+    pub fn pick(&mut self, n: u8) {
+        self.emit_op(Opcode::Pick);
+        self.write_u8(n);
+    }
+
+    pub fn unpick(&mut self, n: u8) {
+        self.emit_op(Opcode::Unpick);
+        self.write_u8(n);
+    }
+
+    pub fn nop(&mut self) {
+        self.emit_op(Opcode::Nop);
+    }
+
+    pub fn lineno(&mut self, lineno: u32) {
+        self.emit_op(Opcode::Lineno);
+        self.write_u32(lineno);
+    }
+
+    pub fn nop_destructuring(&mut self) {
+        self.emit_op(Opcode::NopDestructuring);
+    }
+
+    pub fn force_interpreter(&mut self) {
+        self.emit_op(Opcode::ForceInterpreter);
+    }
+
+    pub fn debug_check_self_hosted(&mut self) {
+        self.emit_op(Opcode::DebugCheckSelfHosted);
+    }
+
+    pub fn debugger(&mut self) {
+        self.emit_op(Opcode::Debugger);
+    }
+
+    // @@@@ END METHODS @@@@
+
+    pub fn get_atom_gcthing_index(&mut self, atom: SourceAtomSetIndex) -> GCThingIndex {
+        match self.atom_to_gcindex_map.get(&atom) {
+            Some(index) => *index,
+            None => {
+                let index = self.gcthings.push_atom(atom);
+                self.atom_to_gcindex_map.insert(atom, index);
+                index
+            }
+        }
+    }
+
+    pub fn get_function_gcthing_index(&mut self, fun_index: ScriptStencilIndex) -> GCThingIndex {
+        self.gcthings.push_function(fun_index)
+    }
+
+    pub fn get_regexp_gcthing_index(&mut self, regexp_index: RegExpIndex) -> GCThingIndex {
+        self.gcthings.push_regexp(regexp_index)
+    }
+
+    fn update_max_frame_slots(&mut self, max_frame_slots: FrameSlot) {
+        self.max_fixed_slots = cmp::max(self.max_fixed_slots, max_frame_slots);
+    }
+
+    pub fn enter_global_scope(&mut self, scope_index: ScopeIndex) {
+        let index = self.gcthings.push_scope(scope_index);
+        self.body_scope_index = Some(index);
+    }
+
+    pub fn leave_global_scope(&self) {}
+
+    pub fn enter_lexical_scope(
+        &mut self,
+        scope_index: ScopeIndex,
+        parent_scope_note_index: Option<ScopeNoteIndex>,
+        next_frame_slot: FrameSlot,
+        needs_environment_object: bool,
+    ) -> ScopeNoteIndex {
+        self.update_max_frame_slots(next_frame_slot);
+
+        let gcthing_index = self.gcthings.push_scope(scope_index);
+        let offset = self.bytecode_offset();
+        let note_index =
+            self.scope_notes
+                .enter_scope(gcthing_index, offset, parent_scope_note_index);
+
+        if needs_environment_object {
+            self.push_lexical_env(gcthing_index);
+        }
+
+        note_index
+    }
+
+    pub fn leave_lexical_scope(&mut self, index: ScopeNoteIndex, needs_environment_object: bool) {
+        self.emit_leave_lexical_scope(needs_environment_object);
+        let offset = self.bytecode_offset();
+        self.scope_notes.leave_scope(index, offset);
+    }
+
+    fn emit_leave_lexical_scope(&mut self, needs_environment_object: bool) {
+        if needs_environment_object {
+            self.pop_lexical_env();
+        } else {
+            self.debug_leave_lexical_env();
+        }
+    }
+
+    pub fn enter_scope_hole_from_lexical(
+        &mut self,
+        maybe_hole_scope_note_index: &Option<ScopeNoteIndex>,
+        parent_scope_note_index: Option<ScopeNoteIndex>,
+        needs_environment_object: bool,
+    ) -> ScopeNoteIndex {
+        self.emit_leave_lexical_scope(needs_environment_object);
+        self.enter_scope_hole(maybe_hole_scope_note_index, parent_scope_note_index)
+    }
+
+    fn enter_scope_hole(
+        &mut self,
+        maybe_hole_scope_note_index: &Option<ScopeNoteIndex>,
+        parent_scope_note_index: Option<ScopeNoteIndex>,
+    ) -> ScopeNoteIndex {
+        let offset = self.bytecode_offset();
+
+        let gcthing_index = match maybe_hole_scope_note_index {
+            Some(index) => self.scope_notes.get_scope_hole_gcthing_index(index),
+            None => self
+                .body_scope_index
+                .expect("we should have a body scope index"),
+        };
+
+        self.scope_notes
+            .enter_scope(gcthing_index, offset, parent_scope_note_index)
+    }
+
+    pub fn leave_scope_hole(&mut self, index: ScopeNoteIndex) {
+        let offset = self.bytecode_offset();
+        self.scope_notes.leave_scope(index, offset);
+    }
+
+    pub fn switch_to_main(&mut self) {
+        self.main_offset = self.bytecode_offset();
+    }
+
+    pub fn into_stencil(
+        self,
+        script_data_list: &mut ImmutableScriptDataList,
+        extent: SourceExtent,
+    ) -> Result<ScriptStencil, EmitError> {
+        let main_offset: usize = self.main_offset.into();
+        let nfixed: u32 = self.max_fixed_slots.into();
+        let nslots = nfixed as usize + self.maximum_stack_depth;
+
+        let immutable_script_data = script_data_list.push(ImmutableScriptData {
+            main_offset: main_offset
+                .try_into()
+                .map_err(|_| EmitError::NotImplemented("Throwing allocation overflow"))?,
+            nfixed: self.max_fixed_slots,
+            nslots: nslots
+                .try_into()
+                .map_err(|_| EmitError::NotImplemented("Throwing JSMSG_NEED_DIET"))?,
+            body_scope_index: usize::from(self.body_scope_index.expect("body scope should be set"))
+                .try_into()
+                .map_err(|_| EmitError::NotImplemented("Throwing allocation overflow"))?,
+            num_ic_entries: self.num_ic_entries.try_into().unwrap(),
+            fun_length: 0,
+
+            bytecode: self.bytecode,
+            scope_notes: self.scope_notes.into(),
+        });
+
+        Ok(ScriptStencil::top_level_script(
+            self.gcthings.into(),
+            immutable_script_data,
+            extent,
+        ))
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/emitter_scope.rs b/third_party/rust/jsparagus-emitter/src/emitter_scope.rs
new file mode 100644
index 0000000000..193ac3f844
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/emitter_scope.rs
@@ -0,0 +1,453 @@
+//! Code for tracking scopes and looking up names as the emitter traverses
+//! the program.
+//!
+//! EmitterScopes exist only while the bytecode emitter is working.
+//! Longer-lived scope information is stored in `ScopeDataMap`.
+
+use crate::emitter::InstructionWriter;
+use ast::source_atom_set::SourceAtomSetIndex;
+use std::collections::HashMap;
+use std::iter::Iterator;
+use stencil::env_coord::{EnvironmentHops, EnvironmentSlot};
+use stencil::frame_slot::FrameSlot;
+use stencil::scope::{BindingKind, GlobalScopeData, LexicalScopeData, ScopeDataMap, ScopeIndex};
+use stencil::scope_notes::ScopeNoteIndex;
+
+/// Result of looking up a name.
+///
+/// Corresponds to js::frontend::NameLocation in
+/// m-c/js/src/frontend/NameAnalysisTypes.h
+#[derive(Debug, Clone)]
+pub enum NameLocation {
+    Dynamic,
+    Global(BindingKind),
+    FrameSlot(FrameSlot, BindingKind),
+    EnvironmentCoord(EnvironmentHops, EnvironmentSlot, BindingKind),
+}
+
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub struct EmitterScopeDepth {
+    index: usize,
+}
+
+impl EmitterScopeDepth {
+    fn has_parent(&self) -> bool {
+        self.index > 0
+    }
+
+    fn parent(&self) -> Self {
+        debug_assert!(self.has_parent());
+
+        Self {
+            index: self.index - 1,
+        }
+    }
+}
+
+// --- EmitterScope types
+//
+// These types are the variants of enum EmitterScope.
+
+#[derive(Debug)]
+pub struct GlobalEmitterScope {
+    cache: HashMap<SourceAtomSetIndex, NameLocation>,
+}
+
+impl GlobalEmitterScope {
+    fn new(data: &GlobalScopeData) -> Self {
+        let mut cache = HashMap::new();
+        for item in data.iter() {
+            cache.insert(item.name(), NameLocation::Global(item.kind()));
+        }
+        Self { cache }
+    }
+
+    fn lookup_name(&self, name: SourceAtomSetIndex) -> Option<NameLocation> {
+        match self.cache.get(&name) {
+            Some(loc) => Some(loc.clone()),
+            None => Some(NameLocation::Global(BindingKind::Var)),
+        }
+    }
+
+    fn next_frame_slot(&self) -> FrameSlot {
+        FrameSlot::new(0)
+    }
+
+    fn scope_note_index(&self) -> Option<ScopeNoteIndex> {
+        None
+    }
+
+    fn has_environment_object(&self) -> bool {
+        false
+    }
+}
+
+struct LexicalEnvironmentObject {}
+impl LexicalEnvironmentObject {
+    fn first_free_slot() -> u32 {
+        // FIXME: This is the value of
+        //   `JSSLOT_FREE(&LexicalEnvironmentObject::class_)`
+        // in SpiderMonkey
+        2
+    }
+}
+
+#[derive(Debug)]
+pub struct LexicalEmitterScope {
+    cache: HashMap<SourceAtomSetIndex, NameLocation>,
+    next_frame_slot: FrameSlot,
+    needs_environment_object: bool,
+    scope_note_index: Option<ScopeNoteIndex>,
+}
+
+impl LexicalEmitterScope {
+    pub fn new(data: &LexicalScopeData, first_frame_slot: FrameSlot) -> Self {
+        let is_all_bindings_closed_over = data.base.is_all_bindings_closed_over();
+        let mut needs_environment_object = false;
+
+        let mut cache = HashMap::new();
+        let mut frame_slot = first_frame_slot;
+        let mut env_slot = EnvironmentSlot::new(LexicalEnvironmentObject::first_free_slot());
+        for item in data.iter() {
+            if is_all_bindings_closed_over || item.is_closed_over() {
+                cache.insert(
+                    item.name(),
+                    NameLocation::EnvironmentCoord(EnvironmentHops::new(0), env_slot, item.kind()),
+                );
+                env_slot.next();
+                needs_environment_object = true;
+            } else {
+                cache.insert(
+                    item.name(),
+                    NameLocation::FrameSlot(frame_slot, item.kind()),
+                );
+                frame_slot.next();
+            }
+        }
+
+        Self {
+            cache,
+            next_frame_slot: frame_slot,
+            needs_environment_object,
+            scope_note_index: None,
+        }
+    }
+
+    fn lookup_name(&self, name: SourceAtomSetIndex) -> Option<NameLocation> {
+        match self.cache.get(&name) {
+            Some(loc) => Some(loc.clone()),
+            None => None,
+        }
+    }
+
+    fn next_frame_slot(&self) -> FrameSlot {
+        self.next_frame_slot
+    }
+
+    fn scope_note_index(&self) -> Option<ScopeNoteIndex> {
+        self.scope_note_index
+    }
+
+    pub fn has_environment_object(&self) -> bool {
+        self.needs_environment_object
+    }
+}
+
+/// The information about a scope needed for emitting bytecode.
+#[derive(Debug)]
+pub enum EmitterScope {
+    Global(GlobalEmitterScope),
+    Lexical(LexicalEmitterScope),
+}
+
+impl EmitterScope {
+    fn lookup_name(&self, name: SourceAtomSetIndex) -> Option<NameLocation> {
+        match self {
+            EmitterScope::Global(scope) => scope.lookup_name(name),
+            EmitterScope::Lexical(scope) => scope.lookup_name(name),
+        }
+    }
+
+    fn next_frame_slot(&self) -> FrameSlot {
+        match self {
+            EmitterScope::Global(scope) => scope.next_frame_slot(),
+            EmitterScope::Lexical(scope) => scope.next_frame_slot(),
+        }
+    }
+
+    pub fn scope_note_index(&self) -> Option<ScopeNoteIndex> {
+        match self {
+            EmitterScope::Global(scope) => scope.scope_note_index(),
+            EmitterScope::Lexical(scope) => scope.scope_note_index(),
+        }
+    }
+
+    fn has_environment_object(&self) -> bool {
+        match self {
+            EmitterScope::Global(scope) => scope.has_environment_object(),
+            EmitterScope::Lexical(scope) => scope.has_environment_object(),
+        }
+    }
+
+    fn is_var_scope(&self) -> bool {
+        match self {
+            EmitterScope::Global(_) => true,
+            EmitterScope::Lexical(_) => false,
+        }
+    }
+}
+
+/// Stack that tracks the current scope chain while emitting bytecode.
+///
+/// Bytecode is emitted by traversing the structure of the program. During this
+/// process there's always a "current position". This stack represents the
+/// scope chain at the current position. It is updated when we enter or leave
+/// any node that has its own scope.
+///
+/// Unlike the C++ impl, this uses an explicit stack struct, since Rust cannot
+/// store a reference to a stack-allocated object in another object that has a
+/// longer lifetime.
+pub struct EmitterScopeStack {
+    scope_stack: Vec<EmitterScope>,
+}
+
+impl EmitterScopeStack {
+    /// Create a new, empty scope stack.
+    pub fn new() -> Self {
+        Self {
+            scope_stack: Vec::new(),
+        }
+    }
+
+    /// The current innermost scope.
+    fn innermost(&self) -> &EmitterScope {
+        self.scope_stack
+            .last()
+            .expect("There should be at least one scope")
+    }
+
+    /// Enter the global scope. Call this once at the beginning of a top-level
+    /// script.
+    ///
+    /// This emits bytecode that implements parts of [ScriptEvaluation][1] and
+    /// [GlobalDeclarationInstantiation][2].
+    ///
+    /// [1]: https://tc39.es/ecma262/#sec-runtime-semantics-scriptevaluation
+    /// [2]: https://tc39.es/ecma262/#sec-globaldeclarationinstantiation
+    pub fn enter_global(
+        &mut self,
+        emit: &mut InstructionWriter,
+        scope_data_map: &ScopeDataMap,
+        top_level_function_count: u32,
+    ) {
+        let scope_index = scope_data_map.get_global_index();
+        let scope_data = scope_data_map.get_global_at(scope_index);
+
+        // The outermost scope should be the first item in the GC things list.
+        // Enter global scope here, before emitting any name ops below.
+        emit.enter_global_scope(scope_index);
+
+        if scope_data.base.bindings.len() > 0 {
+            emit.global_or_eval_decl_instantiation(top_level_function_count);
+        }
+
+        emit.switch_to_main();
+
+        let scope = EmitterScope::Global(GlobalEmitterScope::new(scope_data));
+        self.scope_stack.push(scope);
+    }
+
+    /// Leave the global scope. Call this once at the end of a top-level
+    /// script.
+    pub fn leave_global(&mut self, emit: &InstructionWriter) {
+        match self.scope_stack.pop() {
+            Some(EmitterScope::Global(_)) => {}
+            _ => panic!("unmatching scope"),
+        }
+        emit.leave_global_scope();
+    }
+
+    /// Emit bytecode to mark some local lexical variables as uninitialized.
+    fn dead_zone_frame_slot_range(
+        &self,
+        emit: &mut InstructionWriter,
+        slot_start: FrameSlot,
+        slot_end: FrameSlot,
+    ) {
+        if slot_start == slot_end {
+            return;
+        }
+
+        emit.uninitialized();
+        let mut slot = slot_start;
+        while slot < slot_end {
+            emit.init_lexical(slot.into());
+            slot.next();
+        }
+        emit.pop();
+    }
+
+    /// Enter a lexical scope.
+    ///
+    /// A new LexicalEmitterScope based on scope_data_map is pushed to the
+    /// scope stack. Bytecode is emitted to mark the new lexical bindings as
+    /// uninitialized.
+    pub fn enter_lexical(
+        &mut self,
+        emit: &mut InstructionWriter,
+        scope_data_map: &mut ScopeDataMap,
+        scope_index: ScopeIndex,
+    ) {
+        let mut scope_data = scope_data_map.get_lexical_at_mut(scope_index);
+
+        let parent_scope_note_index = self.innermost().scope_note_index();
+
+        let first_frame_slot = self.innermost().next_frame_slot();
+        scope_data.first_frame_slot = first_frame_slot;
+        let mut lexical_scope = LexicalEmitterScope::new(scope_data, first_frame_slot);
+        let next_frame_slot = lexical_scope.next_frame_slot;
+        let index = emit.enter_lexical_scope(
+            scope_index,
+            parent_scope_note_index,
+            next_frame_slot,
+            lexical_scope.needs_environment_object,
+        );
+        lexical_scope.scope_note_index = Some(index);
+
+        let scope = EmitterScope::Lexical(lexical_scope);
+        self.scope_stack.push(scope);
+
+        self.dead_zone_frame_slot_range(emit, first_frame_slot, next_frame_slot);
+    }
+
+    /// Leave a lexical scope.
+    pub fn leave_lexical(&mut self, emit: &mut InstructionWriter) {
+        let lexical_scope = match self.scope_stack.pop() {
+            Some(EmitterScope::Lexical(scope)) => scope,
+            _ => panic!("unmatching scope"),
+        };
+        emit.leave_lexical_scope(
+            lexical_scope
+                .scope_note_index
+                .expect("scope note index should be populated"),
+            lexical_scope.needs_environment_object,
+        );
+    }
+
+    /// Resolve a name by searching the current scope chain.
+    ///
+    /// Implements the parts of [ResolveBinding][1] that can be done at
+    /// emit time.
+    ///
+    /// [1]: https://tc39.es/ecma262/#sec-resolvebinding
+    pub fn lookup_name(&mut self, name: SourceAtomSetIndex) -> NameLocation {
+        let mut hops = EnvironmentHops::new(0);
+
+        for scope in self.scope_stack.iter().rev() {
+            if let Some(loc) = scope.lookup_name(name) {
+                return match loc {
+                    NameLocation::EnvironmentCoord(orig_hops, slot, kind) => {
+                        debug_assert!(u8::from(orig_hops) == 0u8);
+                        NameLocation::EnvironmentCoord(hops, slot, kind)
+                    }
+                    _ => loc,
+                };
+            }
+            if scope.has_environment_object() {
+                hops.next();
+            }
+        }
+
+        NameLocation::Dynamic
+    }
+
+    /// Just like lookup_name, but only in var scope.
+    pub fn lookup_name_in_var(&mut self, name: SourceAtomSetIndex) -> NameLocation {
+        let mut hops = EnvironmentHops::new(0);
+
+        for scope in self.scope_stack.iter().rev() {
+            if scope.is_var_scope() {
+                if let Some(loc) = scope.lookup_name(name) {
+                    return match loc {
+                        NameLocation::EnvironmentCoord(orig_hops, slot, kind) => {
+                            debug_assert!(u8::from(orig_hops) == 0u8);
+                            NameLocation::EnvironmentCoord(hops, slot, kind)
+                        }
+                        _ => loc,
+                    };
+                }
+            }
+
+            if scope.has_environment_object() {
+                hops.next();
+            }
+        }
+
+        NameLocation::Dynamic
+    }
+
+    pub fn current_depth(&self) -> EmitterScopeDepth {
+        EmitterScopeDepth {
+            index: self.scope_stack.len() - 1,
+        }
+    }
+
+    /// Walk the scope stack up to and including `to` depth.
+    /// See EmitterScopeWalker for the details.
+    pub fn walk_up_to_including<'a>(&'a self, to: EmitterScopeDepth) -> EmitterScopeWalker<'a> {
+        EmitterScopeWalker::new(self, to)
+    }
+
+    pub fn get_current_scope_note_index(&self) -> Option<ScopeNoteIndex> {
+        self.innermost().scope_note_index()
+    }
+
+    fn get<'a>(&'a self, index: EmitterScopeDepth) -> &'a EmitterScope {
+        self.scope_stack
+            .get(index.index)
+            .expect("scope should exist")
+    }
+}
+
+/// Walk the scope stack up to `to`, and yields EmitterScopeWalkItem for
+/// each scope.
+///
+/// The first item is `{ outer: parent-of-innermost, inner: innermost }`, and
+/// the last item is `{ outer: to, inner: child-of-to }`.
+pub struct EmitterScopeWalker<'a> {
+    stack: &'a EmitterScopeStack,
+    to: EmitterScopeDepth,
+    current: EmitterScopeDepth,
+}
+
+impl<'a> EmitterScopeWalker<'a> {
+    fn new(stack: &'a EmitterScopeStack, to: EmitterScopeDepth) -> Self {
+        let current = stack.current_depth();
+
+        Self { stack, to, current }
+    }
+}
+
+pub struct EmitterScopeWalkItem<'a> {
+    pub outer: &'a EmitterScope,
+    pub inner: &'a EmitterScope,
+}
+
+impl<'a> Iterator for EmitterScopeWalker<'a> {
+    type Item = EmitterScopeWalkItem<'a>;
+
+    fn next(&mut self) -> Option<EmitterScopeWalkItem<'a>> {
+        if self.current == self.to {
+            return None;
+        }
+
+        let outer_index = self.current.parent();
+        let inner_index = self.current;
+        self.current = outer_index;
+
+        Some(EmitterScopeWalkItem {
+            inner: self.stack.get(inner_index),
+            outer: self.stack.get(outer_index),
+        })
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/expression_emitter.rs b/third_party/rust/jsparagus-emitter/src/expression_emitter.rs
new file mode 100644
index 0000000000..45f0e10664
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/expression_emitter.rs
@@ -0,0 +1,31 @@
+use crate::ast_emitter::AstEmitter;
+use crate::emitter::EmitError;
+
+pub struct ExpressionEmitter<F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub expr: F,
+}
+
+impl<F> ExpressionEmitter<F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack]
+
+        (self.expr)(emitter)?;
+        //              [stack] VAL
+
+        if emitter.options.no_script_rval {
+            emitter.emit.pop();
+        //          [stack]
+        } else {
+            emitter.emit.set_rval();
+            //          [stack]
+        }
+
+        Ok(())
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/function_declaration_emitter.rs b/third_party/rust/jsparagus-emitter/src/function_declaration_emitter.rs
new file mode 100644
index 0000000000..5eefd5b215
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/function_declaration_emitter.rs
@@ -0,0 +1,77 @@
+use crate::ast_emitter::AstEmitter;
+use crate::emitter::EmitError;
+use crate::reference_op_emitter::{
+    AssignmentEmitter, DeclarationEmitter, GetNameEmitter, NameReferenceEmitter,
+};
+use ast::source_atom_set::SourceAtomSetIndex;
+use stencil::gcthings::GCThingIndex;
+use stencil::script::ScriptStencilIndex;
+
+pub struct LazyFunctionEmitter {
+    pub stencil_index: ScriptStencilIndex,
+}
+
+impl LazyFunctionEmitter {
+    pub fn emit(self, emitter: &mut AstEmitter) -> GCThingIndex {
+        emitter
+            .compilation_info
+            .scripts
+            .get_mut(self.stencil_index)
+            .set_function_emitted();
+        emitter.emit.get_function_gcthing_index(self.stencil_index)
+    }
+}
+
+pub struct LexicalFunctionDeclarationEmitter {
+    pub name: SourceAtomSetIndex,
+    pub fun_index: GCThingIndex,
+}
+
+impl LexicalFunctionDeclarationEmitter {
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        DeclarationEmitter {
+            lhs: |emitter| {
+                Ok(NameReferenceEmitter { name: self.name }.emit_for_declaration(emitter))
+            },
+            rhs: |emitter| {
+                emitter.emit.lambda(self.fun_index);
+                Ok(())
+            },
+        }
+        .emit(emitter)?;
+
+        emitter.emit.pop();
+
+        Ok(())
+    }
+}
+
+pub struct AnnexBFunctionDeclarationEmitter {
+    pub name: SourceAtomSetIndex,
+    pub fun_index: GCThingIndex,
+}
+
+impl AnnexBFunctionDeclarationEmitter {
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        LexicalFunctionDeclarationEmitter {
+            name: self.name,
+            fun_index: self.fun_index,
+        }
+        .emit(emitter)?;
+
+        AssignmentEmitter {
+            lhs: |emitter| {
+                Ok(NameReferenceEmitter { name: self.name }.emit_for_var_assignment(emitter))
+            },
+            rhs: |emitter| {
+                GetNameEmitter { name: self.name }.emit(emitter);
+                Ok(())
+            },
+        }
+        .emit(emitter)?;
+
+        emitter.emit.pop();
+
+        Ok(())
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/lib.rs b/third_party/rust/jsparagus-emitter/src/lib.rs
new file mode 100644
index 0000000000..e4b5d49bc1
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/lib.rs
@@ -0,0 +1,177 @@
+mod array_emitter;
+mod ast_emitter;
+mod block_emitter;
+mod compilation_info;
+mod control_structures;
+mod dis;
+mod emitter;
+mod emitter_scope;
+mod expression_emitter;
+mod function_declaration_emitter;
+mod object_emitter;
+mod reference_op_emitter;
+mod script_emitter;
+
+extern crate jsparagus_ast as ast;
+extern crate jsparagus_scope as scope;
+extern crate jsparagus_stencil as stencil;
+
+pub use crate::emitter::{EmitError, EmitOptions};
+pub use dis::dis;
+
+use crate::compilation_info::CompilationInfo;
+
+use ast::source_atom_set::SourceAtomSet;
+use ast::source_slice_list::SourceSliceList;
+use scope::{ScopeBuildError, ScopePassResult};
+use stencil::result::EmitResult;
+
+pub fn emit<'alloc>(
+    ast: &'alloc ast::types::Program<'alloc>,
+    options: &EmitOptions,
+    atoms: SourceAtomSet<'alloc>,
+    slices: SourceSliceList<'alloc>,
+) -> Result<EmitResult<'alloc>, EmitError> {
+    let ScopePassResult {
+        scope_data_map,
+        function_declarations,
+        function_stencil_indices,
+        function_declaration_properties,
+        scripts,
+        error,
+    } = scope::generate_scope_data(ast);
+
+    // Error case for scope analysis will be removed once all syntax is
+    // supported. Use field instead of Result type here for simplicity.
+    match error {
+        Some(ScopeBuildError::NotImplemented(s)) => {
+            return Err(EmitError::NotImplemented(s));
+        }
+        None => {}
+    }
+
+    let compilation_info = CompilationInfo::new(
+        atoms,
+        slices,
+        scope_data_map,
+        function_declarations,
+        function_stencil_indices,
+        function_declaration_properties,
+        scripts,
+    );
+    ast_emitter::emit_program(ast, options, compilation_info)
+}
+
+#[cfg(test)]
+mod tests {
+    extern crate jsparagus_parser as parser;
+
+    use super::{emit, EmitOptions};
+    use crate::dis::*;
+    use ast::source_atom_set::SourceAtomSet;
+    use ast::source_slice_list::SourceSliceList;
+    use bumpalo::Bump;
+    use parser::{parse_script, ParseOptions};
+    use std::cell::RefCell;
+    use std::convert::TryInto;
+    use std::rc::Rc;
+    use stencil::opcode::*;
+    use stencil::script::SourceExtent;
+
+    fn bytecode(source: &str) -> Vec<u8> {
+        let alloc = &Bump::new();
+        let parse_options = ParseOptions::new();
+        let atoms = Rc::new(RefCell::new(SourceAtomSet::new()));
+        let slices = Rc::new(RefCell::new(SourceSliceList::new()));
+        let source_len = source.len();
+        let parse_result =
+            parse_script(alloc, source, &parse_options, atoms.clone(), slices.clone())
+                .expect("Failed to parse");
+        // println!("{:?}", parse_result);
+
+        let extent = SourceExtent::top_level_script(source_len.try_into().unwrap(), 1, 0);
+        let emit_options = EmitOptions::new(extent);
+
+        let result = emit(
+            alloc.alloc(ast::types::Program::Script(parse_result.unbox())),
+            &emit_options,
+            atoms.replace(SourceAtomSet::new_uninitialized()),
+            slices.replace(SourceSliceList::new()),
+        )
+        .expect("Should work!");
+
+        let script_data_index: usize = result.scripts[0]
+            .immutable_script_data
+            .expect("Top level script should have ImmutableScriptData")
+            .into();
+        let script_data = &result.script_data_list[script_data_index];
+        let bytecode = &script_data.bytecode;
+
+        println!("{}", dis(&bytecode));
+        bytecode.to_vec()
+    }
+
+    #[test]
+    fn it_works() {
+        assert_eq!(
+            bytecode("2 + 2"),
+            vec![
+                Opcode::Int8 as u8,
+                2,
+                Opcode::Int8 as u8,
+                2,
+                Opcode::Add as u8,
+                Opcode::SetRval as u8,
+                Opcode::RetRval as u8,
+            ]
+        )
+    }
+
+    #[test]
+    fn dis_call() {
+        assert_eq!(
+            bytecode("dis()"),
+            vec![
+                Opcode::GetGName as u8,
+                1,
+                0,
+                0,
+                0,
+                Opcode::Undefined as u8,
+                Opcode::Call as u8,
+                0,
+                0,
+                Opcode::SetRval as u8,
+                Opcode::RetRval as u8,
+            ]
+        )
+    }
+
+    #[test]
+    fn literals() {
+        assert_eq!(
+            bytecode("true"),
+            vec![
+                Opcode::True as u8,
+                Opcode::SetRval as u8,
+                Opcode::RetRval as u8,
+            ]
+        );
+        assert_eq!(
+            bytecode("false"),
+            vec![
+                Opcode::False as u8,
+                Opcode::SetRval as u8,
+                Opcode::RetRval as u8,
+            ]
+        );
+        //assert_eq!(
+        //    bytecode("'hello world'"),
+        //    vec![
+        //        Opcode::String as u8, 0, 0, 0, 0,
+        //        Opcode::SetRval as u8,
+        //        Opcode::RetRval as u8,
+        //    ]
+        //);
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/object_emitter.rs b/third_party/rust/jsparagus-emitter/src/object_emitter.rs
new file mode 100644
index 0000000000..9f77382aa4
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/object_emitter.rs
@@ -0,0 +1,162 @@
+use crate::ast_emitter::AstEmitter;
+use crate::emitter::EmitError;
+use ast::source_atom_set::SourceAtomSetIndex;
+
+/// Struct for emitting bytecode for a property where its name is string.
+///
+/// If the property name is a string representing a number, it is considered an
+/// index. In this case, NamePropertyEmitter falls back internally to
+/// IndexPropertyEmitter
+pub struct NamePropertyEmitter<'a, F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub state: &'a mut ObjectEmitterState,
+    pub key: SourceAtomSetIndex,
+    pub value: F,
+}
+
+impl<'a, F> NamePropertyEmitter<'a, F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack] OBJ
+
+        match self.to_property_index(emitter, self.key) {
+            Some(value) => {
+                IndexPropertyEmitter {
+                    state: self.state,
+                    key: value as f64,
+                    value: self.value,
+                }
+                .emit(emitter)?;
+                //      [stack] OBJ
+            }
+            None => {
+                let name_index = emitter.emit.get_atom_gcthing_index(self.key);
+
+                (self.value)(emitter)?;
+                //      [stack] OBJ VALUE
+
+                emitter.emit.init_prop(name_index);
+                //      [stack] OBJ
+            }
+        }
+        Ok(())
+    }
+
+    fn to_property_index(
+        &self,
+        emitter: &mut AstEmitter,
+        index: SourceAtomSetIndex,
+    ) -> Option<u32> {
+        let s = emitter.compilation_info.atoms.get(index);
+        s.parse::<u32>().ok()
+    }
+}
+
+/// Struct for emitting bytecode for a property where its name is number.
+pub struct IndexPropertyEmitter<'a, F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub state: &'a mut ObjectEmitterState,
+    pub key: f64,
+    pub value: F,
+}
+
+impl<'a, F> IndexPropertyEmitter<'a, F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack] OBJ
+
+        emitter.emit.numeric(self.key);
+        //              [stack] OBJ KEY
+
+        (self.value)(emitter)?;
+        //              [stack] OBJ KEY VALUE
+
+        emitter.emit.init_elem();
+        //              [stack] OBJ
+
+        Ok(())
+    }
+}
+
+/// Struct for emitting bytecode for a computed property.
+pub struct ComputedPropertyEmitter<'a, F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub state: &'a mut ObjectEmitterState,
+    pub key: F1,
+    pub value: F2,
+}
+
+impl<'a, F1, F2> ComputedPropertyEmitter<'a, F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack] OBJ
+
+        (self.key)(emitter)?;
+        //              [stack] OBJ KEY
+
+        (self.value)(emitter)?;
+        //              [stack] OBJ KEY VALUE
+
+        emitter.emit.init_elem();
+        //              [stack] OBJ
+
+        Ok(())
+    }
+}
+
+/// No state so far.
+struct ObjectEmitterStateInternal {}
+
+/// Opaque struct that can be created only by ObjectEmitter.
+/// This guarantees that *PropertyEmitter structs cannot be used outside
+/// of ObjectEmitter callback.
+pub struct ObjectEmitterState(ObjectEmitterStateInternal);
+
+impl ObjectEmitterState {
+    fn new() -> Self {
+        Self(ObjectEmitterStateInternal {})
+    }
+}
+
+pub struct ObjectEmitter<'a, PropT, PropF>
+where
+    PropF: Fn(&mut AstEmitter, &mut ObjectEmitterState, &PropT) -> Result<(), EmitError>,
+{
+    pub properties: std::slice::Iter<'a, PropT>,
+    pub prop: PropF,
+}
+
+impl<'a, PropT, PropF> ObjectEmitter<'a, PropT, PropF>
+where
+    PropF: Fn(&mut AstEmitter, &mut ObjectEmitterState, &PropT) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack]
+
+        emitter.emit.new_init();
+        //              [stack] OBJ
+
+        let mut state = ObjectEmitterState::new();
+
+        for prop in self.properties {
+            (self.prop)(emitter, &mut state, prop)?;
+            //          [stack] OBJ
+        }
+
+        Ok(())
+    }
+}
diff --git a/third_party/rust/jsparagus-emitter/src/reference_op_emitter.rs b/third_party/rust/jsparagus-emitter/src/reference_op_emitter.rs
new file mode 100644
index 0000000000..4a784e5b04
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/reference_op_emitter.rs
@@ -0,0 +1,829 @@
+use crate::ast_emitter::AstEmitter;
+use crate::emitter::EmitError;
+use crate::emitter_scope::NameLocation;
+use ast::source_atom_set::SourceAtomSetIndex;
+use stencil::env_coord::{EnvironmentHops, EnvironmentSlot};
+use stencil::frame_slot::FrameSlot;
+use stencil::gcthings::GCThingIndex;
+use stencil::scope::BindingKind;
+
+#[derive(Debug, PartialEq)]
+enum AssignmentReferenceKind {
+    GlobalVar(GCThingIndex),
+    GlobalLexical(GCThingIndex),
+    FrameSlotLexical(FrameSlot),
+    FrameSlotNonLexical(FrameSlot),
+    EnvironmentCoordLexical(EnvironmentHops, EnvironmentSlot),
+    EnvironmentCoordNonLexical(EnvironmentHops, EnvironmentSlot),
+    Dynamic(GCThingIndex),
+    #[allow(dead_code)]
+    Prop(GCThingIndex),
+    #[allow(dead_code)]
+    Elem,
+}
+
+// See AssignmentReferenceEmitter.
+// This uses struct to hide the details from the consumer.
+#[derive(Debug)]
+#[must_use]
+pub struct AssignmentReference {
+    kind: AssignmentReferenceKind,
+}
+impl AssignmentReference {
+    fn new(kind: AssignmentReferenceKind) -> Self {
+        Self { kind }
+    }
+
+    fn stack_slots(&self) -> usize {
+        match self.kind {
+            AssignmentReferenceKind::GlobalVar(_) => 1,
+            AssignmentReferenceKind::GlobalLexical(_) => 1,
+            AssignmentReferenceKind::FrameSlotLexical(_) => 0,
+            AssignmentReferenceKind::FrameSlotNonLexical(_) => 0,
+            AssignmentReferenceKind::EnvironmentCoordLexical(_, _) => 0,
+            AssignmentReferenceKind::EnvironmentCoordNonLexical(_, _) => 0,
+            AssignmentReferenceKind::Dynamic(_) => 1,
+            AssignmentReferenceKind::Prop(_) => 1,
+            AssignmentReferenceKind::Elem => 2,
+        }
+    }
+}
+
+#[derive(Debug, PartialEq)]
+enum DeclarationReferenceKind {
+    GlobalVar(GCThingIndex),
+    GlobalLexical(GCThingIndex),
+    FrameSlot(FrameSlot),
+    EnvironmentCoord(EnvironmentHops, EnvironmentSlot),
+}
+
+// See DeclarationReferenceEmitter.
+// This uses struct to hide the details from the consumer.
+#[derive(Debug)]
+#[must_use]
+pub struct DeclarationReference {
+    kind: DeclarationReferenceKind,
+}
+impl DeclarationReference {
+    fn new(kind: DeclarationReferenceKind) -> Self {
+        Self { kind }
+    }
+}
+
+#[derive(Debug, PartialEq)]
+enum CallKind {
+    Normal,
+    // FIXME: Support eval, Function#call, Function#apply etc.
+}
+
+#[derive(Debug, PartialEq)]
+enum ValueIsOnStack {
+    No,
+    Yes,
+}
+
+fn check_frame_temporary_dead_zone(
+    emitter: &mut AstEmitter,
+    slot: FrameSlot,
+    is_on_stack: ValueIsOnStack,
+) {
+    // FIXME: Use cache to avoid emitting check_lexical twice or more.
+    // FIXME: Support aliased lexical.
+
+    //                  [stack] VAL?
+
+    if is_on_stack == ValueIsOnStack::No {
+        emitter.emit.get_local(slot.into());
+        //              [stack] VAL
+    }
+
+    emitter.emit.check_lexical(slot.into());
+    //                  [stack] VAL
+
+    if is_on_stack == ValueIsOnStack::No {
+        emitter.emit.pop();
+        //              [stack]
+    }
+
+    //                  [stack] VAL?
+}
+
+fn check_env_temporary_dead_zone(
+    emitter: &mut AstEmitter,
+    hops: EnvironmentHops,
+    slot: EnvironmentSlot,
+    is_on_stack: ValueIsOnStack,
+) {
+    // FIXME: Use cache to avoid emitting check_lexical twice or more.
+    // FIXME: Support aliased lexical.
+
+    //                  [stack] VAL?
+
+    if is_on_stack == ValueIsOnStack::No {
+        emitter.emit.get_aliased_var(hops.into(), slot.into());
+        //              [stack] VAL
+    }
+
+    emitter.emit.check_aliased_lexical(hops.into(), slot.into());
+    //                  [stack] VAL
+
+    if is_on_stack == ValueIsOnStack::No {
+        emitter.emit.pop();
+        //              [stack]
+    }
+
+    //                  [stack] VAL?
+}
+
+// See *ReferenceEmitter.
+// This uses struct to hide the details from the consumer.
+#[derive(Debug)]
+#[must_use]
+pub struct CallReference {
+    kind: CallKind,
+}
+impl CallReference {
+    fn new(kind: CallKind) -> Self {
+        Self { kind }
+    }
+}
+
+// Struct for emitting bytecode for get `name` operation.
+pub struct GetNameEmitter {
+    pub name: SourceAtomSetIndex,
+}
+impl GetNameEmitter {
+    pub fn emit(self, emitter: &mut AstEmitter) {
+        let name_index = emitter.emit.get_atom_gcthing_index(self.name);
+        let loc = emitter.lookup_name(self.name);
+
+        //              [stack]
+
+        match loc {
+            NameLocation::Global(_kind) => {
+                emitter.emit.get_g_name(name_index);
+                //      [stack] VAL
+            }
+            NameLocation::Dynamic => {
+                emitter.emit.get_name(name_index);
+                //      [stack] VAL
+            }
+            NameLocation::FrameSlot(slot, kind) => {
+                emitter.emit.get_local(slot.into());
+                //      [stack] VAL
+
+                if kind == BindingKind::Let || kind == BindingKind::Const {
+                    check_frame_temporary_dead_zone(emitter, slot, ValueIsOnStack::Yes);
+                    //  [stack] VAL
+                }
+            }
+            NameLocation::EnvironmentCoord(hops, slot, kind) => {
+                emitter.emit.get_aliased_var(hops.into(), slot.into());
+
+                if kind == BindingKind::Let || kind == BindingKind::Const {
+                    check_env_temporary_dead_zone(emitter, hops, slot, ValueIsOnStack::Yes);
+                    //  [stack] VAL
+                }
+            }
+        }
+    }
+}
+
+// Struct for emitting bytecode for get `obj.key` operation.
+pub struct GetPropEmitter<F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub obj: F,
+    pub key: SourceAtomSetIndex,
+}
+impl<F> GetPropEmitter<F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        let key_index = emitter.emit.get_atom_gcthing_index(self.key);
+
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        (self.obj)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] OBJ
+
+        emitter.emit.get_prop(key_index);
+        //              [stack] VAL
+
+        Ok(())
+    }
+}
+
+// Struct for emitting bytecode for get `super.key` operation.
+pub struct GetSuperPropEmitter<F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub this: F,
+    pub key: SourceAtomSetIndex,
+}
+impl<F> GetSuperPropEmitter<F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        let key_index = emitter.emit.get_atom_gcthing_index(self.key);
+
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        (self.this)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] THIS
+
+        emitter.emit.callee();
+        //              [stack] THIS CALLEE
+
+        emitter.emit.super_base();
+        //              [stack] THIS OBJ
+
+        emitter.emit.get_prop_super(key_index);
+        //              [stack] VAL
+
+        Ok(())
+    }
+}
+
+// Struct for emitting bytecode for get `obj[key]` operation.
+pub struct GetElemEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub obj: F1,
+    pub key: F2,
+}
+impl<F1, F2> GetElemEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        (self.obj)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] OBJ
+
+        let depth = emitter.emit.stack_depth();
+        (self.key)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] OBJ KEY
+
+        emitter.emit.get_elem();
+        //              [stack] VAL
+
+        Ok(())
+    }
+}
+
+// Struct for emitting bytecode for get `super[key]` operation.
+pub struct GetSuperElemEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub this: F1,
+    pub key: F2,
+}
+impl<F1, F2> GetSuperElemEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        (self.this)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] THIS
+
+        let depth = emitter.emit.stack_depth();
+        (self.key)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] THIS KEY
+
+        emitter.emit.callee();
+        //              [stack] THIS KEY CALLEE
+
+        emitter.emit.super_base();
+        //              [stack] THIS KEY OBJ
+
+        emitter.emit.get_elem_super();
+        //              [stack] VAL
+
+        Ok(())
+    }
+}
+
+// Struct for emitting bytecode for `name` reference.
+pub struct NameReferenceEmitter {
+    pub name: SourceAtomSetIndex,
+}
+impl NameReferenceEmitter {
+    pub fn emit_for_call(self, emitter: &mut AstEmitter) -> CallReference {
+        let name_index = emitter.emit.get_atom_gcthing_index(self.name);
+        let loc = emitter.lookup_name(self.name);
+
+        //              [stack]
+
+        match loc {
+            NameLocation::Global(_kind) => {
+                emitter.emit.get_g_name(name_index);
+                //      [stack] CALLEE
+
+                // NOTE: We don't support non-syntactic scope.
+                //       See NameOpEmitter::emitGet in SpiderMonkey for omitted
+                //       cases.
+
+                emitter.emit.undefined();
+                //      [stack] CALLEE THIS
+            }
+            NameLocation::Dynamic => {
+                emitter.emit.get_name(name_index);
+                //      [stack] CALLEE
+
+                // NOTE: We don't support non-syntactic scope or with statement.
+                //       See NameOpEmitter::emitGet in SpiderMonkey for omitted
+                //       cases.
+
+                emitter.emit.undefined();
+                //      [stack] CALLEE THIS
+            }
+            NameLocation::FrameSlot(slot, kind) => {
+                emitter.emit.get_local(slot.into());
+                //      [stack] CALLEE
+
+                if kind == BindingKind::Let || kind == BindingKind::Const {
+                    check_frame_temporary_dead_zone(emitter, slot, ValueIsOnStack::Yes);
+                    //  [stack] CALLEE
+                }
+
+                emitter.emit.undefined();
+                //      [stack] CALLEE THIS
+            }
+            NameLocation::EnvironmentCoord(hops, slot, kind) => {
+                emitter.emit.get_aliased_var(hops.into(), slot.into());
+                //      [stack] CALLEE
+
+                if kind == BindingKind::Let || kind == BindingKind::Const {
+                    check_env_temporary_dead_zone(emitter, hops, slot, ValueIsOnStack::Yes);
+                    //  [stack] CALLEE
+                }
+
+                emitter.emit.undefined();
+                //      [stack] CALLEE THIS
+            }
+        }
+
+        CallReference::new(CallKind::Normal)
+    }
+
+    pub fn emit_for_assignment_with_loc(
+        self,
+        emitter: &mut AstEmitter,
+        loc: NameLocation,
+    ) -> AssignmentReference {
+        let name_index = emitter.emit.get_atom_gcthing_index(self.name);
+
+        //              [stack]
+
+        match loc {
+            NameLocation::Global(kind) => match kind {
+                BindingKind::Var => {
+                    emitter.emit.bind_g_name(name_index);
+                    //  [stack] GLOBAL
+                    AssignmentReference::new(AssignmentReferenceKind::GlobalVar(name_index))
+                }
+                BindingKind::Let | BindingKind::Const => {
+                    emitter.emit.bind_g_name(name_index);
+                    //  [stack] GLOBAL
+                    AssignmentReference::new(AssignmentReferenceKind::GlobalLexical(name_index))
+                }
+            },
+            NameLocation::Dynamic => {
+                emitter.emit.bind_name(name_index);
+                //      [stack] ENV
+
+                AssignmentReference::new(AssignmentReferenceKind::Dynamic(name_index))
+            }
+            NameLocation::FrameSlot(slot, kind) => {
+                if kind == BindingKind::Let || kind == BindingKind::Const {
+                    AssignmentReference::new(AssignmentReferenceKind::FrameSlotLexical(slot))
+                } else {
+                    AssignmentReference::new(AssignmentReferenceKind::FrameSlotNonLexical(slot))
+                }
+            }
+            NameLocation::EnvironmentCoord(hops, slot, kind) => {
+                if kind == BindingKind::Let || kind == BindingKind::Const {
+                    AssignmentReference::new(AssignmentReferenceKind::EnvironmentCoordLexical(
+                        hops, slot,
+                    ))
+                } else {
+                    AssignmentReference::new(AssignmentReferenceKind::EnvironmentCoordNonLexical(
+                        hops, slot,
+                    ))
+                }
+            }
+        }
+    }
+
+    pub fn emit_for_assignment(self, emitter: &mut AstEmitter) -> AssignmentReference {
+        let loc = emitter.lookup_name(self.name);
+        self.emit_for_assignment_with_loc(emitter, loc)
+    }
+
+    /// Ignore any lexical scope and assign to var scope.
+    /// Used by Annex B function.
+    pub fn emit_for_var_assignment(self, emitter: &mut AstEmitter) -> AssignmentReference {
+        let loc = emitter.lookup_name_in_var(self.name);
+        self.emit_for_assignment_with_loc(emitter, loc)
+    }
+
+    pub fn emit_for_declaration(self, emitter: &mut AstEmitter) -> DeclarationReference {
+        let name_index = emitter.emit.get_atom_gcthing_index(self.name);
+        let loc = emitter.lookup_name(self.name);
+
+        //              [stack]
+
+        match loc {
+            NameLocation::Global(kind) => match kind {
+                BindingKind::Var => {
+                    emitter.emit.bind_g_name(name_index);
+                    //  [stack] GLOBAL
+                    DeclarationReference::new(DeclarationReferenceKind::GlobalVar(name_index))
+                }
+                BindingKind::Let | BindingKind::Const => {
+                    DeclarationReference::new(DeclarationReferenceKind::GlobalLexical(name_index))
+                }
+            },
+            NameLocation::Dynamic => {
+                panic!("declaration should have non-dynamic location");
+            }
+            NameLocation::FrameSlot(slot, _kind) => {
+                DeclarationReference::new(DeclarationReferenceKind::FrameSlot(slot))
+            }
+            NameLocation::EnvironmentCoord(hops, slot, _kind) => {
+                // FIXME: does this happen????
+                DeclarationReference::new(DeclarationReferenceKind::EnvironmentCoord(hops, slot))
+            }
+        }
+    }
+}
+
+// Struct for emitting bytecode for `obj.key` reference.
+pub struct PropReferenceEmitter<F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub obj: F,
+    pub key: SourceAtomSetIndex,
+}
+impl<F> PropReferenceEmitter<F>
+where
+    F: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit_for_call(self, emitter: &mut AstEmitter) -> Result<CallReference, EmitError> {
+        let key_index = emitter.emit.get_atom_gcthing_index(self.key);
+
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        (self.obj)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] THIS
+
+        emitter.emit.dup();
+        //              [stack] THIS THIS
+
+        // FIXME: Support super.
+        emitter.emit.get_prop(key_index);
+        //              [stack] THIS CALLEE
+
+        emitter.emit.swap();
+        //              [stack] CALLEE THIS
+
+        Ok(CallReference::new(CallKind::Normal))
+    }
+
+    #[allow(dead_code)]
+    pub fn emit_for_assignment(
+        self,
+        emitter: &mut AstEmitter,
+    ) -> Result<AssignmentReference, EmitError> {
+        let key_index = emitter.emit.get_atom_gcthing_index(self.key);
+
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        (self.obj)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] OBJ
+
+        Ok(AssignmentReference::new(AssignmentReferenceKind::Prop(
+            key_index,
+        )))
+    }
+}
+
+// Struct for emitting bytecode for `obj[key]` reference.
+pub struct ElemReferenceEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub obj: F1,
+    pub key: F2,
+}
+impl<F1, F2> ElemReferenceEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit_for_call(self, emitter: &mut AstEmitter) -> Result<CallReference, EmitError> {
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        (self.obj)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] THIS
+
+        emitter.emit.dup();
+        //              [stack] THIS THIS
+
+        let depth = emitter.emit.stack_depth();
+        (self.key)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] THIS THIS KEY
+
+        // FIXME: Support super.
+        emitter.emit.get_elem();
+        //              [stack] THIS CALLEE
+
+        emitter.emit.swap();
+        //              [stack] CALLEE THIS
+
+        Ok(CallReference::new(CallKind::Normal))
+    }
+
+    #[allow(dead_code)]
+    pub fn emit_for_assignment(
+        self,
+        emitter: &mut AstEmitter,
+    ) -> Result<AssignmentReference, EmitError> {
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        (self.obj)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] OBJ
+
+        let depth = emitter.emit.stack_depth();
+        (self.key)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] OBJ KEY
+
+        Ok(AssignmentReference::new(AssignmentReferenceKind::Elem))
+    }
+}
+
+// Struct for emitting bytecode for call `callee(arguments)` operation.
+pub struct CallEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<CallReference, EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<usize, EmitError>,
+{
+    pub callee: F1,
+    pub arguments: F2,
+}
+impl<F1, F2> CallEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<CallReference, EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<usize, EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        let reference = (self.callee)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 2);
+        //              [stack] CALLEE THIS
+
+        // FIXME: Support spread.
+        let depth = emitter.emit.stack_depth();
+        let len = (self.arguments)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + len);
+        //              [stack] CALLEE THIS ARGS...
+
+        match reference.kind {
+            CallKind::Normal => {
+                emitter.emit.call(len as u16);
+                //      [stack] VAL
+            }
+        }
+
+        Ok(())
+    }
+}
+
+// Struct for emitting bytecode for `new callee(arguments)` operation.
+pub struct NewEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<usize, EmitError>,
+{
+    pub callee: F1,
+    pub arguments: F2,
+}
+impl<F1, F2> NewEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<usize, EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        (self.callee)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] CALLEE
+
+        emitter.emit.is_constructing();
+        //              [stack] CALLEE JS_IS_CONSTRUCTING
+
+        // FIXME: Support spread.
+        let depth = emitter.emit.stack_depth();
+        let len = (self.arguments)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + len);
+        //              [stack] CALLEE JS_IS_CONSTRUCTING ARGS...
+
+        emitter.emit.dup_at(len as u32 + 1);
+        //              [stack] CALLEE JS_IS_CONSTRUCTING ARGS... CALLEE
+
+        emitter.emit.new_(len as u16);
+        //              [stack] VAL
+
+        Ok(())
+    }
+}
+
+// Struct for emitting bytecode for assignment `lhs = rhs` operation.
+pub struct AssignmentEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<AssignmentReference, EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub lhs: F1,
+    pub rhs: F2,
+}
+impl<F1, F2> AssignmentEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<AssignmentReference, EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        //              [stack]
+
+        let depth = emitter.emit.stack_depth();
+        let reference = (self.lhs)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + reference.stack_slots());
+        //              [stack] REF...
+
+        let depth = emitter.emit.stack_depth();
+        (self.rhs)(emitter)?;
+        debug_assert_eq!(emitter.emit.stack_depth(), depth + 1);
+        //              [stack] REF... VAL
+
+        match reference.kind {
+            AssignmentReferenceKind::GlobalVar(name_index) => {
+                //      [stack] GLOBAL VAL
+
+                emitter.emit.set_g_name(name_index);
+                //      [stack] VAL
+            }
+            AssignmentReferenceKind::GlobalLexical(name_index) => {
+                //      [stack] VAL
+
+                emitter.emit.set_g_name(name_index);
+                //      [stack] VAL
+            }
+            AssignmentReferenceKind::Dynamic(name_index) => {
+                //      [stack] ENV VAL
+
+                emitter.emit.set_name(name_index);
+                //      [stack] VAL
+            }
+            AssignmentReferenceKind::FrameSlotLexical(slot) => {
+                //      [stack] VAL
+
+                check_frame_temporary_dead_zone(emitter, slot, ValueIsOnStack::No);
+                //      [stack] VAL
+
+                emitter.emit.set_local(slot.into());
+                //      [stack] VAL
+            }
+            AssignmentReferenceKind::FrameSlotNonLexical(slot) => {
+                //      [stack] VAL
+
+                emitter.emit.set_local(slot.into());
+                //      [stack] VAL
+            }
+            AssignmentReferenceKind::EnvironmentCoordLexical(hops, slot) => {
+                //      [stack] VAL
+
+                check_env_temporary_dead_zone(emitter, hops, slot, ValueIsOnStack::No);
+                //      [stack] VAL
+
+                emitter.emit.set_aliased_var(hops.into(), slot.into());
+                //      [stack] VAL
+            }
+            AssignmentReferenceKind::EnvironmentCoordNonLexical(hops, slot) => {
+                //      [stack] VAL
+
+                emitter.emit.set_aliased_var(hops.into(), slot.into());
+                //      [stack] VAL
+            }
+            AssignmentReferenceKind::Prop(key_index) => {
+                //      [stack] OBJ VAL
+
+                // FIXME: Support strict mode and super.
+                emitter.emit.set_prop(key_index);
+                //      [stack] VAL
+            }
+            AssignmentReferenceKind::Elem => {
+                //      [stack] OBJ KEY VAL
+
+                // FIXME: Support strict mode and super.
+                emitter.emit.set_elem();
+                //      [stack] VAL
+            }
+        }
+
+        Ok(())
+    }
+
+    // FIXME: Support compound assignment
+}
+
+// Struct for emitting bytecode for declaration `lhs = rhs` operation.
+pub struct DeclarationEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<DeclarationReference, EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub lhs: F1,
+    pub rhs: F2,
+}
+impl<F1, F2> DeclarationEmitter<F1, F2>
+where
+    F1: Fn(&mut AstEmitter) -> Result<DeclarationReference, EmitError>,
+    F2: Fn(&mut AstEmitter) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        let reference = (self.lhs)(emitter)?;
+
+        (self.rhs)(emitter)?;
+
+        match reference.kind {
+            DeclarationReferenceKind::GlobalVar(name_index) => {
+                //      [stack] GLOBAL VAL
+
+                emitter.emit.set_g_name(name_index);
+                //      [stack] VAL
+            }
+            DeclarationReferenceKind::GlobalLexical(name_index) => {
+                //      [stack] VAL
+
+                emitter.emit.init_g_lexical(name_index);
+                //      [stack] VAL
+            }
+            DeclarationReferenceKind::FrameSlot(slot) => {
+                //      [stack] VAL
+
+                emitter.emit.init_lexical(slot.into());
+                //      [stack] VAL
+            }
+            DeclarationReferenceKind::EnvironmentCoord(hops, slot) => {
+                //      [stack] VAL
+
+                emitter.emit.init_aliased_lexical(hops.into(), slot.into());
+                //      [stack] VAL
+            }
+        }
+
+        Ok(())
+    }
+}
+
+// FIXME: Add increment
diff --git a/third_party/rust/jsparagus-emitter/src/script_emitter.rs b/third_party/rust/jsparagus-emitter/src/script_emitter.rs
new file mode 100644
index 0000000000..36c24ca594
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/script_emitter.rs
@@ -0,0 +1,43 @@
+use crate::ast_emitter::AstEmitter;
+use crate::emitter::EmitError;
+
+pub struct ScriptEmitter<'a, FuncT, FuncF, StmtT, StmtF>
+where
+    FuncF: Fn(&mut AstEmitter, &FuncT) -> Result<(), EmitError>,
+    StmtF: Fn(&mut AstEmitter, &StmtT) -> Result<(), EmitError>,
+{
+    pub top_level_functions: std::slice::Iter<'a, FuncT>,
+    pub top_level_function: FuncF,
+    pub statements: std::slice::Iter<'a, StmtT>,
+    pub statement: StmtF,
+}
+
+impl<'a, FuncT, FuncF, StmtT, StmtF> ScriptEmitter<'a, FuncT, FuncF, StmtT, StmtF>
+where
+    FuncF: Fn(&mut AstEmitter, &FuncT) -> Result<(), EmitError>,
+    StmtF: Fn(&mut AstEmitter, &StmtT) -> Result<(), EmitError>,
+{
+    pub fn emit(self, emitter: &mut AstEmitter) -> Result<(), EmitError> {
+        let scope_data_map = &emitter.compilation_info.scope_data_map;
+
+        emitter.scope_stack.enter_global(
+            &mut emitter.emit,
+            scope_data_map,
+            self.top_level_functions.len() as u32,
+        );
+
+        for fun in self.top_level_functions {
+            (self.top_level_function)(emitter, fun)?;
+        }
+
+        for statement in self.statements {
+            (self.statement)(emitter, statement)?;
+        }
+
+        emitter.emit.ret_rval();
+
+        emitter.scope_stack.leave_global(&mut emitter.emit);
+
+        Ok(())
+    }
+}