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LibJS: Add a scope object abstraction

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Both GlobalObject and LexicalEnvironment now inherit from ScopeObject,
and the VM's call frames point to a ScopeObject chain rather than just
a LexicalEnvironment chain.

This gives us much more flexibility to implement things like "with",
and also unifies some of the code paths that previously required
special handling of the global object.

There's a bunch of more cleanup that can be done in the wake of this
change, and there might be some oversights in the handling of the
"super" keyword, but this generally seems like a good architectural
improvement. :^)
This commit is contained in:
Andreas Kling 2020-11-28 16:02:27 +01:00
parent e1bbc7c075
commit c3fe9b4df8
16 changed files with 241 additions and 92 deletions
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17
Libraries/LibJS/Interpreter.cpp
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@ -72,8 +72,7 @@ Value Interpreter::run(GlobalObject& global_object, const Program& program)
global_call_frame.this_value = &global_object;
static FlyString global_execution_context_name = "(global execution context)";
global_call_frame.function_name = global_execution_context_name;
global_call_frame.environment = heap().allocate<LexicalEnvironment>(global_object, LexicalEnvironment::EnvironmentRecordType::Global);
global_call_frame.environment->bind_this_value(global_object, &global_object);
global_call_frame.scope = &global_object;
ASSERT(!vm.exception());
global_call_frame.is_strict_mode = program.is_strict_mode();
vm.push_call_frame(global_call_frame, global_object);
@ -96,7 +95,7 @@ const GlobalObject& Interpreter::global_object() const
void Interpreter::enter_scope(const ScopeNode& scope_node, ArgumentVector arguments, ScopeType scope_type, GlobalObject& global_object)
{
for (auto& declaration : scope_node.functions()) {
auto* function = ScriptFunction::create(global_object, declaration.name(), declaration.body(), declaration.parameters(), declaration.function_length(), current_environment(), declaration.is_strict_mode());
auto* function = ScriptFunction::create(global_object, declaration.name(), declaration.body(), declaration.parameters(), declaration.function_length(), current_scope(), declaration.is_strict_mode());
vm().set_variable(declaration.name(), function, global_object);
}
@ -127,8 +126,8 @@ void Interpreter::enter_scope(const ScopeNode& scope_node, ArgumentVector argume
bool pushed_lexical_environment = false;
if (!scope_variables_with_declaration_kind.is_empty()) {
auto* block_lexical_environment = heap().allocate<LexicalEnvironment>(global_object, move(scope_variables_with_declaration_kind), current_environment());
vm().call_frame().environment = block_lexical_environment;
auto* block_lexical_environment = heap().allocate<LexicalEnvironment>(global_object, move(scope_variables_with_declaration_kind), current_scope());
vm().call_frame().scope = block_lexical_environment;
pushed_lexical_environment = true;
}
@ -140,7 +139,7 @@ void Interpreter::exit_scope(const ScopeNode& scope_node)
while (!m_scope_stack.is_empty()) {
auto popped_scope = m_scope_stack.take_last();
if (popped_scope.pushed_environment)
vm().call_frame().environment = vm().call_frame().environment->parent();
vm().call_frame().scope = vm().call_frame().scope->parent();
if (popped_scope.scope_node.ptr() == &scope_node)
break;
}
@ -185,4 +184,10 @@ Value Interpreter::execute_statement(GlobalObject& global_object, const Statemen
return did_return ? vm().last_value() : js_undefined();
}
LexicalEnvironment* Interpreter::current_environment()
{
ASSERT(vm().call_frame().scope->is_lexical_environment());
return static_cast<LexicalEnvironment*>(vm().call_frame().scope);
}
}