Previously, the function only handled a single level of member access,
producing strings like "<object>.isWall" for chained expressions like
"graphSet[j][k].isWall". Now it recurses through nested member
expressions, identifiers, string/numeric literals, and `this`.
When MemberExpression::generate_bytecode calls emit_load_from_reference,
it only uses the loaded_value and discards the reference operands. For
computed member expressions (e.g. a[0]), this was generating an
unnecessary Mov to save the property register for potential store-back.
Add a ReferenceMode parameter to emit_load_from_reference. When LoadOnly
is passed, the computed property path skips the register save and Mov.
Per AssignmentRestElement and AssignmentElement in the specification,
the DestructuringAssignmentTarget reference must be evaluated before
iterating or stepping the iterator. We were doing it in the wrong
order, which caused observable differences when the target evaluation
has side effects, and could lead to infinite loops when the iterator
never completes.
Add Generator::emit_evaluate_reference() to evaluate a member
expression's base and property into ReferenceOperands without performing
a load or store, then use the pre-evaluated reference for the store
after iteration completes.
When a function has parameter expressions (e.g. destructured params with
defaults), CreateVariableEnvironment creates a separate variable
environment for function declarations and sets it as the current lexical
environment at runtime. However, the bytecode generator's
m_lexical_environment_register_stack was not updated to reflect this, so
subsequent CreateLexicalEnvironment ops would parent themselves to the
old (pre-variable-environment) lexical environment, skipping the
variable environment entirely.
This meant function declarations hoisted into the variable environment
were invisible to closures created in the function body.
Fix this by capturing the new lexical environment into a register after
CreateVariableEnvironment and pushing it onto the environment register
stack.
This fixes a problem where https://tumblr.com/ wouldn't load the feed.
AsyncIteratorClose is now fully inlined as bytecode in ASTCodegen.cpp,
using the Await bytecode op to yield naturally. The C++ implementation
used synchronous await() which spins the event loop, violating
assertions when execution contexts are on the stack.
The AsyncIteratorClose bytecode op calls async_iterator_close() which
uses synchronous await() internally. This spins the event loop while
execution contexts are on the stack, violating the microtask checkpoint
assertion in LibWeb.
Replace AsyncIteratorClose op emissions in for-await-of close handlers
with inline bytecode that uses the proper Await op, allowing the async
function to yield and resume naturally through the event loop.
For the non-throw path (break/return/continue-to-outer): emit
GetMethod, Call, Await, and ThrowIfNotObject inline.
For the throw path: wrap the close steps in an exception handler so
that any error from GetMethod/Call/Await is discarded and the original
exception is rethrown, per spec step 5.
The else branch already throws ReferenceError and switches to a dead
basic block, so the emit_todo() in the PutValue section is unreachable.
Return early after the throw and replace emit_todo() with
VERIFY_NOT_REACHED().
CallExpression is accepted as an assignment target for web compatibility
(Annex B), but must throw ReferenceError at runtime. We were incorrectly
throwing TypeError with a TODO message.
Replace emit_todo() calls in three codegen paths (simple assignment,
compound assignment/update, and for-in/of) with proper ReferenceError
using the "Invalid left-hand side in assignment" message, matching the
behavior of V8 and JSC.
When a for-of or for-await-of loop exits via break, return, throw,
or continue-to-outer-loop, we now correctly call IteratorClose
(or AsyncIteratorClose) to give the iterator a chance to clean
up resources.
This uses a synthetic FinallyContext that wraps the LHS assignment
and loop body, reusing the existing try/finally completion record
machinery. The ReturnToFinally boundary is placed between Break
and Continue so that continue-to-same-loop bypasses the close
(zero overhead on normal iteration) while all other abrupt exits
route through the iterator close dispatch chain.
for-in (enumerate) does not require iterator close per spec.
Change the completion_value field from Optional<Value> to Operand
in both IteratorClose and AsyncIteratorClose bytecode instructions.
This allows passing a dynamic value from a register, which is needed
for iterator close on abrupt completion where the exception value
is not known at codegen time.
Remove CodeGenerationError and make all bytecode generation functions
return their results directly instead of wrapping them in
CodeGenerationErrorOr.
For the few remaining sites where codegen encounters an unimplemented
or unexpected AST node, we now use a new emit_todo() helper that emits
a NewTypeError + Throw sequence at compile time (preserving the runtime
behavior) and then switches to a dead basic block so subsequent codegen
for the same function can continue without issue.
This allows us to remove error handling from all callers of the
bytecode compiler, simplifying the code significantly.
These checks validate engine-internal usage of builtin abstract
operations (arity, argument types, known operation names), not user JS
code. Replace CodeGenerationError returns with VERIFY() assertions:
- Spread argument check becomes VERIFY(!argument.is_spread)
- Arity checks become VERIFY(arguments.size() == N)
- StringLiteral type checks become VERIFY(message)
- Unknown operation/constant fallthroughs become VERIFY_NOT_REACHED()
Replace CodeGenerationError returns with VERIFY_NOT_REACHED() or
VERIFY() at sites that are provably unreachable:
- Non-computed member expression fallbacks in emit_load_from_reference,
emit_store_to_reference, and emit_delete_reference (member expression
properties are always computed, identifier, or private identifier)
- Two non-computed member expression fallbacks in AssignmentExpression
- Default case in compound assignment switch (all 15 AssignmentOp values
are handled)
- BindingPattern Empty/Expression name+alias pair (computed property
names always require an alias)
- Two assignment+destructuring combinations in for-in/of body evaluation
(is_destructuring is only set for VariableDeclaration lhs, which
always has VarBinding or LexicalBinding kind, never Assignment)
When a class field has a BigInt literal key like `128n = class {}`,
the anonymous class should get the name "128". The codegen path
handles Identifier, StringLiteral, and NumericLiteral keys but was
missing BigInt keys, causing the name to be empty.
Parse the BigInt literal value at codegen time and convert it to a
decimal string for both the field_name (anonymous function naming)
and class_field_initializer_name (eval("arguments") checking) paths.
Change NativeJavaScriptBackedFunction::create() to accept an
already-created GC::Ref<SharedFunctionInstanceData> instead of a
FunctionNode const&, removing another point of AST-runtime coupling.
SharedFunctionInstanceData::m_source_text is a Utf16View into the
SourceCode that the function was parsed from. Previously, the
SourceCode was kept alive transitively through the AST nodes.
As we move towards dropping AST nodes after compilation, we need to
ensure the SourceCode outlives the view. Add a RefPtr<SourceCode>
to SharedFunctionInstanceData so m_source_text remains valid even
after the AST is gone. This is needed for Function.prototype.toString
which accesses source_text() at any point during the function's
lifetime.
Add static factory methods create_for_function_node() on
SharedFunctionInstanceData and update all callers to use them instead
of FunctionNode::ensure_shared_data().
This removes the GC::Root<SharedFunctionInstanceData> cache from
FunctionNode, eliminating the coupling between the RefCounted AST
and GC-managed runtime objects. The cache was effectively dead code:
hoisted declarations use m_functions_to_initialize directly, and
function expressions always create fresh instances during codegen.
Remove create_for_per_iteration_bindings(Badge<ForStatement>) and
initialize_or_set_mutable_binding(Badge<ScopeNode>) which have zero
callers anywhere in the codebase.
parse_builtin_file() previously returned FunctionDeclaration AST nodes
stored in static vectors, keeping the full AST alive for the entire
process lifetime. Change it to return SharedFunctionInstanceData
objects directly, allowing the parsed Program and its AST nodes to be
freed when the function returns.
Each SharedFunctionInstanceData holds its own ref to the function body
AST via m_ecmascript_code, which is automatically dropped when
clear_compile_inputs() runs after first bytecode compilation.
Now that initialize_environment() uses pre-computed data and
execute_module() caches its executable / uses TLA shared data,
we can drop the AST reference after it's no longer needed.
For TLA modules, the AST is dropped immediately after constructing
the SharedFunctionInstanceData (which takes its own ref). For non-TLA
modules, the AST is dropped after the first bytecode compilation.
Also remove the m_default_export field (replaced by the pre-computed
m_default_export_binding_name) and extract default export info in
parse() instead of the constructor.
For non-TLA modules, cache the compiled Bytecode::Executable on the
SourceTextModule so we only compile once.
For TLA modules, pre-create the SharedFunctionInstanceData for the
async wrapper function at construction time. The wrapper function's
first invocation will compile it to bytecode and then automatically
drop the AST via clear_compile_inputs().
Extract the data needed by initialize_environment() from the AST at
construction time, following the pattern already used by Script for
global declaration instantiation.
This pre-computes var declared names, lexical bindings (with function
indices), functions to initialize (with SharedFunctionInstanceData),
and the default export binding name.
Change ImportEntry and ExportEntry to store Optional<ModuleRequest>
by value instead of raw pointers into AST storage. This decouples the
entry records from AST node lifetimes, preparing for dropping the AST
from SourceTextModule after first compilation.
Change eval_declaration_instantiation to take EvalDeclarationData&
instead of Program const&. The function body now iterates
pre-computed name lists instead of walking the AST.
Both callers (perform_eval and perform_shadow_realm_eval) now build
EvalDeclarationData before calling eval_declaration_instantiation.
This decouples the runtime declaration-instantiation API from AST
types, matching the pattern already used by Script for global
declaration instantiation.
Add EvalDeclarationData struct that holds pre-computed metadata
extracted from the Program AST: var names, functions to initialize,
declared function names, var scoped names, AnnexB candidates, and
lexical bindings.
This mirrors the pattern used by Script for global declaration
instantiation, and prepares for decoupling
eval_declaration_instantiation from the AST.
After compiling the bytecode executable on first run, null out the
AST (m_parse_node) and clear AnnexB candidates since they are no
longer needed. This frees the memory held by the entire AST for the
script's lifetime.
The parse_node() accessor now returns a nullable pointer. Callers
(js.cpp for AST dumping, Interpreter for first compilation) access
the AST before it is dropped.
Add Script::global_declaration_instantiation() that performs the GDI
algorithm using pre-computed name lists and shared function data
instead of walking the AST.
Runtime checks (has_lexical_declaration, can_declare_global_function,
etc.) remain since they depend on global environment state. AnnexB
iterates pre-collected candidates and calls
set_should_do_additional_annexB_steps() on stored refs.
The Interpreter::run(Script&) now calls the Script method instead of
the Program method.
Extract all data that Program::global_declaration_instantiation()
needs from the AST into value-type metadata stored on the Script
object, computed once during construction. This includes lexical
names, var names, functions to initialize, var scoped names, AnnexB
candidates, and lexical bindings.
This prepares for rewriting GDI to use the pre-computed metadata
instead of walking the AST.
Extract FunctionParsingInsights into its own header and introduce
FunctionLocal as a standalone mirror of Identifier::Local. This
allows SharedFunctionInstanceData.h to avoid pulling in the full
AST type hierarchy, reducing transitive include bloat.
The AST.h include is kept in SharedFunctionInstanceData.cpp where
it's needed for the constructor that accesses AST node types.
