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LibJS: Follow the spec more closely when determining the this value

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Co-authored-by: davidot <david.tuin@gmail.com>
This commit is contained in:
Timothy Flynn 2021-07-12 01:37:51 +02:00 • committed by Andreas Kling
parent a394aa5830
commit c6e9c6d6ab
3 changed files with 36 additions and 11 deletions
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8
Userland/Libraries/LibJS/AST.cpp
View file

@ -161,12 +161,8 @@ CallExpression::ThisAndCallee CallExpression::compute_this_and_callee(Interprete
return { this_value, callee };
}
if (interpreter.vm().in_strict_mode()) {
// If we are in strict mode, |this| should never be bound to global object by default.
return { js_undefined(), m_callee->execute(interpreter, global_object) };
}
return { &global_object, m_callee->execute(interpreter, global_object) };
// [[Call]] will handle that in non-strict mode the this value becomes the global object
return { js_undefined(), m_callee->execute(interpreter, global_object) };
}
// 13.3.8.1 Runtime Semantics: ArgumentListEvaluation, https://tc39.es/ecma262/#sec-runtime-semantics-argumentlistevaluation

37
Userland/Libraries/LibJS/Runtime/VM.cpp
View file

@ -589,6 +589,36 @@ void VM::prepare_for_ordinary_call(FunctionObject& function, ExecutionContext& c
// 15. Return calleeContext. (See NOTE above about how contexts are allocated on the C++ stack.)
}
// 10.2.1.2 OrdinaryCallBindThis ( F, calleeContext, thisArgument ), https://tc39.es/ecma262/#sec-ordinarycallbindthis
void VM::ordinary_call_bind_this(FunctionObject& function, ExecutionContext& callee_context, Value this_argument)
{
auto this_mode = function.this_mode();
auto* callee_realm = function.realm();
auto* local_environment = callee_context.lexical_environment;
auto& function_environment = verify_cast<FunctionEnvironment>(*local_environment);
// This is not completely as the spec describes it however without this stuff breaks
// (Could be related to the note at https://tc39.es/ecma262/#sec-runtime-semantics-instantiatearrowfunctionexpression )
if (!callee_realm || this_mode == FunctionObject::ThisMode::Lexical) {
function_environment.bind_this_value(function.global_object(), callee_context.this_value);
return;
}
Value this_value;
if (function.is_strict_mode()) {
this_value = this_argument;
} else if (this_argument.is_nullish()) {
auto& global_environment = callee_realm->environment();
this_value = global_environment.global_this_value();
} else {
this_value = this_argument.to_object(function.global_object());
}
function_environment.bind_this_value(function.global_object(), this_value);
callee_context.this_value = this_value;
}
Value VM::call_internal(FunctionObject& function, Value this_value, Optional<MarkedValueList> arguments)
{
VERIFY(!exception());
@ -611,11 +641,8 @@ Value VM::call_internal(FunctionObject& function, Value this_value, Optional<Mar
if (arguments.has_value())
callee_context.arguments.extend(arguments.value().values());
if (auto* environment = callee_context.lexical_environment) {
auto& function_environment = verify_cast<FunctionEnvironment>(*environment);
VERIFY(function_environment.this_binding_status() == FunctionEnvironment::ThisBindingStatus::Uninitialized);
function_environment.bind_this_value(function.global_object(), callee_context.this_value);
}
if (callee_context.lexical_environment)
ordinary_call_bind_this(function, callee_context, this_value);
if (exception())
return {};

2
Userland/Libraries/LibJS/Runtime/VM.h
View file

@ -260,6 +260,8 @@ public:
private:
VM();
void ordinary_call_bind_this(FunctionObject&, ExecutionContext&, Value this_argument);
[[nodiscard]] Value call_internal(FunctionObject&, Value this_value, Optional<MarkedValueList> arguments);
void prepare_for_ordinary_call(FunctionObject&, ExecutionContext& callee_context, Value new_target);