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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
#include "qqmljsshadowcheck_p.h"
QT_BEGIN_NAMESPACE
using namespace Qt::StringLiterals;
/*!
* \internal
* \class QQmlJSShadowCheck
*
* This pass looks for possible shadowing when accessing members of QML-exposed
* types. A member can be shadowed if a non-final property is re-declared in a
* derived class. As the QML engine will always pick up the most derived variant
* of that property, we cannot rely on any property of a type to be actually
* accessible, unless one of a few special cases holds:
*
* 1. We are dealing with a direct scope lookup, without an intermediate object.
* Such lookups are protected from shadowing. For example "property int a: b"
* always works.
* 2. The object we are retrieving the property from is identified by an ID, or
* an attached property or a singleton. Such objects cannot be replaced.
* Therefore we can be sure to see all the type information at compile time.
* 3. The property is declared final.
* 4. The object we are retrieving the property from is a value type. Value
* types cannot be used polymorphically.
*/
void QQmlJSShadowCheck::run(
const InstructionAnnotations *annotations, const Function *function,
QQmlJS::DiagnosticMessage *error)
{
m_annotations = annotations;
m_function = function;
m_error = error;
m_state = initialState(function);
decode(m_function->code.constData(), static_cast<uint>(m_function->code.length()));
}
void QQmlJSShadowCheck::generate_LoadProperty(int nameIndex)
{
auto accumulatorIn = m_state.registers.find(Accumulator);
if (accumulatorIn != m_state.registers.end())
checkShadowing(accumulatorIn.value(), m_jsUnitGenerator->stringForIndex(nameIndex));
}
void QQmlJSShadowCheck::generate_GetLookup(int index)
{
auto accumulatorIn = m_state.registers.find(Accumulator);
if (accumulatorIn != m_state.registers.end())
checkShadowing(accumulatorIn.value(), m_jsUnitGenerator->lookupName(index));
}
void QQmlJSShadowCheck::generate_StoreProperty(int nameIndex, int base)
{
checkShadowing(m_state.registers[base], m_jsUnitGenerator->stringForIndex(nameIndex));
}
void QQmlJSShadowCheck::generate_SetLookup(int index, int base)
{
checkShadowing(m_state.registers[base], m_jsUnitGenerator->lookupName(index));
}
QV4::Moth::ByteCodeHandler::Verdict QQmlJSShadowCheck::startInstruction(QV4::Moth::Instr::Type)
{
m_state = nextStateFromAnnotations(m_state, *m_annotations);
return (m_state.hasSideEffects() || m_state.changedRegisterIndex() != InvalidRegister)
? ProcessInstruction
: SkipInstruction;
}
void QQmlJSShadowCheck::endInstruction(QV4::Moth::Instr::Type)
{
}
void QQmlJSShadowCheck::checkShadowing(
const QQmlJSRegisterContent &baseType, const QString &memberName)
{
if (baseType.storedType()->accessSemantics() != QQmlJSScope::AccessSemantics::Reference)
return;
switch (baseType.variant()) {
case QQmlJSRegisterContent::ObjectProperty:
case QQmlJSRegisterContent::ExtensionObjectProperty:
case QQmlJSRegisterContent::ScopeProperty:
case QQmlJSRegisterContent::ExtensionScopeProperty: {
const QQmlJSRegisterContent member = m_typeResolver->memberType(baseType, memberName);
// You can have something like parent.QtQuick.Screen.pixelDensity
// In that case "QtQuick" cannot be resolved as member type and we would later have to look
// for "QtQuick.Screen" instead. However, you can only do that with attached properties and
// those are not shadowable.
if (!member.isValid()) {
Q_ASSERT(m_typeResolver->isPrefix(memberName));
return;
}
if (member.isProperty()) {
if (member.property().isFinal())
return; // final properties can't be shadowed
} else if (!member.isMethod()) {
return; // Only properties and methods can be shadowed
}
setError(u"Member %1 of %2 can be shadowed"_s
.arg(memberName, m_state.accumulatorIn().descriptiveName()));
return;
}
default:
// In particular ObjectById is fine as that cannot change into something else
// Singleton should also be fine, unless the factory function creates an object
// with different property types than the declared class.
return;
}
}
QT_END_NAMESPACE
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