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/*
* Copyright 2010-2024 JetBrains s.r.o. and Kotlin Programming Language contributors.
* Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
*/
package org.jetbrains.kotlin.fir.expressions
import org.jetbrains.kotlin.config.LanguageFeature
import org.jetbrains.kotlin.descriptors.ClassKind
import org.jetbrains.kotlin.descriptors.Modality
import org.jetbrains.kotlin.fir.*
import org.jetbrains.kotlin.fir.declarations.fullyExpandedClass
import org.jetbrains.kotlin.fir.declarations.hasAnnotation
import org.jetbrains.kotlin.fir.declarations.utils.isConst
import org.jetbrains.kotlin.fir.declarations.utils.isStatic
import org.jetbrains.kotlin.fir.declarations.utils.modality
import org.jetbrains.kotlin.fir.expressions.impl.FirElseIfTrueCondition
import org.jetbrains.kotlin.fir.references.FirErrorNamedReference
import org.jetbrains.kotlin.fir.references.FirResolvedErrorReference
import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
import org.jetbrains.kotlin.fir.references.toResolvedCallableSymbol
import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
import org.jetbrains.kotlin.fir.resolve.toSymbol
import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
import org.jetbrains.kotlin.fir.symbols.impl.*
import org.jetbrains.kotlin.fir.types.*
import org.jetbrains.kotlin.fir.visitors.FirVisitor
import org.jetbrains.kotlin.name.Name
import org.jetbrains.kotlin.name.StandardClassIds
import org.jetbrains.kotlin.util.OperatorNameConventions
fun ConeKotlinType.canBeUsedForConstVal(): Boolean = with(lowerBoundIfFlexible()) { isPrimitive || isString || isUnsignedType }
/**
* See the documentation to [computeConstantExpressionKind] function below
*/
fun canBeEvaluatedAtCompileTime(
expression: FirExpression?,
session: FirSession,
allowErrors: Boolean,
calledOnCheckerStage: Boolean,
): Boolean {
val result = computeConstantExpressionKind(expression, session, calledOnCheckerStage)
return result == ConstantArgumentKind.VALID_CONST || allowErrors && result == ConstantArgumentKind.RESOLUTION_ERROR
}
/**
* This function computes if given [expression] can be counted as a constant expression or not
* It returns a [ConstantArgumentKind], which can be used to understand why exactly the expression is not constant
*
* Precise computation of this [ConstantArgumentKind] may require resolution of initializer of non-const properties, which is allowed
* to do only on BODY_RESOLVE phase and checkers phase. Without it, the result may be less precise but still correct (it may return
* the general [ConstantArgumentKind.NOT_CONST] instead more specific [ConstantArgumentKind.NOT_KCLASS_LITERAL] for example)
*
* So, to allow using this function not only from checkers there is a @param [calledOnCheckerStage], which should be set to [true] ONLY
* if this method is called from checkers
*/
fun computeConstantExpressionKind(
expression: FirExpression?,
session: FirSession,
calledOnCheckerStage: Boolean
): ConstantArgumentKind {
if (expression == null) return ConstantArgumentKind.RESOLUTION_ERROR
return expression.accept(FirConstCheckVisitor(session, calledOnCheckerStage), null)
}
enum class ConstantArgumentKind {
VALID_CONST,
RESOLUTION_ERROR,
NOT_CONST,
ENUM_NOT_CONST,
NOT_KCLASS_LITERAL,
NOT_CONST_VAL_IN_CONST_EXPRESSION,
KCLASS_LITERAL_OF_TYPE_PARAMETER_ERROR;
inline fun ifNotValidConst(action: (ConstantArgumentKind) -> Unit) {
if (this != VALID_CONST) {
action(this)
}
}
}
private class FirConstCheckVisitor(
private val session: FirSession,
val calledOnCheckerStage: Boolean,
) : FirVisitor() {
companion object {
/**
* During constant evaluation, we can go from kotlin world to java world and back (see the example)
*
* Java constants are evaluated using PSI evaluator, which knows nothing about this particular class and no context is provided
* to its entrypoint. So we should somehow track cases of recursion without any context
*
* Since [FirConstCheckVisitor] should be side-effect free, we can't write anything directly in the tree, so it was decided
* to collect the list of properties which were already checked on the constant evaluator path in the thread-local list.
* So when the execution comes back to kotlin after java, this context will be preserved
* ```
* // FILE: Bar.java
* public class Bar {
* public static final int BAR = TestKt.recursion2 + 1;
* }
*
* // FILE: Test.kt
* const val a = recursion1 + 1
*
* const val recursion1 = Bar.BAR + 1
* const val recursion2 = recursion1 + 1
* ```
*/
private val propertyStack: ThreadLocal>> = ThreadLocal.withInitial { mutableListOf() }
private val compileTimeFunctions = setOf(
*OperatorNameConventions.SIMPLE_BINARY_OPERATION_NAMES.toTypedArray(),
*OperatorNameConventions.SIMPLE_UNARY_OPERATION_NAMES.toTypedArray(),
*OperatorNameConventions.SIMPLE_BITWISE_OPERATION_NAMES.toTypedArray(),
OperatorNameConventions.COMPARE_TO
)
private val compileTimeExtensionFunctions = listOf("floorDiv", "mod", "code").mapTo(hashSetOf()) { Name.identifier(it) }
}
private val intrinsicConstEvaluation = session.languageVersionSettings.supportsFeature(LanguageFeature.IntrinsicConstEvaluation)
private fun FirCallableSymbol<*>.visit(block: () -> T?): T? {
propertyStack.get() += this
try {
return block()
} finally {
propertyStack.get().removeLast()
}
}
override fun visitElement(element: FirElement, data: Nothing?): ConstantArgumentKind {
return ConstantArgumentKind.NOT_CONST
}
override fun visitErrorExpression(errorExpression: FirErrorExpression, data: Nothing?): ConstantArgumentKind {
// Error expression already signalizes about some problem, and later we will report some diagnostic.
// Depending on the context, we can count this as valid or as error expression.
// So we delegate the final decision to the caller.
return ConstantArgumentKind.RESOLUTION_ERROR
}
override fun visitNamedArgumentExpression(namedArgumentExpression: FirNamedArgumentExpression, data: Nothing?): ConstantArgumentKind {
return namedArgumentExpression.expression.accept(this, data)
}
override fun visitSpreadArgumentExpression(spreadArgumentExpression: FirSpreadArgumentExpression, data: Nothing?): ConstantArgumentKind {
return spreadArgumentExpression.expression.accept(this, data)
}
override fun visitTypeOperatorCall(typeOperatorCall: FirTypeOperatorCall, data: Nothing?): ConstantArgumentKind {
if (typeOperatorCall.operation != FirOperation.AS) {
return ConstantArgumentKind.NOT_CONST
}
if (!typeOperatorCall.argument.resolvedType.isSubtypeOf(typeOperatorCall.resolvedType, session)) {
return ConstantArgumentKind.NOT_CONST
}
return ConstantArgumentKind.VALID_CONST
}
override fun visitWhenExpression(whenExpression: FirWhenExpression, data: Nothing?): ConstantArgumentKind {
if (!whenExpression.isProperlyExhaustive || !intrinsicConstEvaluation) {
return ConstantArgumentKind.NOT_CONST
}
whenExpression.subject?.accept(this, data)?.ifNotValidConst { return it }
for (branch in whenExpression.branches) {
when (branch.condition) {
is FirElseIfTrueCondition -> { /* skip */ }
else -> branch.condition.accept(this, data).ifNotValidConst { return it }
}
branch.result.statements.forEach { stmt ->
if (stmt !is FirExpression) return ConstantArgumentKind.NOT_CONST
stmt.accept(this, data).ifNotValidConst { return it }
}
}
return ConstantArgumentKind.VALID_CONST
}
override fun visitWhenSubjectExpression(whenSubjectExpression: FirWhenSubjectExpression, data: Nothing?): ConstantArgumentKind {
return if (intrinsicConstEvaluation) ConstantArgumentKind.VALID_CONST else ConstantArgumentKind.NOT_CONST
}
override fun visitLiteralExpression(literalExpression: FirLiteralExpression, data: Nothing?): ConstantArgumentKind {
return ConstantArgumentKind.VALID_CONST
}
override fun visitComparisonExpression(comparisonExpression: FirComparisonExpression, data: Nothing?): ConstantArgumentKind {
return comparisonExpression.compareToCall.accept(this, data)
}
override fun visitStringConcatenationCall(stringConcatenationCall: FirStringConcatenationCall, data: Nothing?): ConstantArgumentKind {
for (exp in stringConcatenationCall.arguments) {
if (exp is FirLiteralExpression && exp.value == null) {
// `null` is allowed
continue
}
if (!exp.hasAllowedCompileTimeType()) {
return ConstantArgumentKind.NOT_CONST
}
exp.accept(this, data).ifNotValidConst { return it }
}
return ConstantArgumentKind.VALID_CONST
}
override fun visitEqualityOperatorCall(equalityOperatorCall: FirEqualityOperatorCall, data: Nothing?): ConstantArgumentKind {
if (equalityOperatorCall.operation == FirOperation.IDENTITY || equalityOperatorCall.operation == FirOperation.NOT_IDENTITY) {
return ConstantArgumentKind.NOT_CONST
}
for (exp in equalityOperatorCall.arguments) {
if (exp is FirLiteralExpression && exp.value == null) {
return ConstantArgumentKind.NOT_CONST
}
if (!exp.hasAllowedCompileTimeType() || exp.getExpandedType().isUnsignedType) {
return ConstantArgumentKind.NOT_CONST
}
exp.accept(this, data).ifNotValidConst { return it }
}
return ConstantArgumentKind.VALID_CONST
}
override fun visitBooleanOperatorExpression(booleanOperatorExpression: FirBooleanOperatorExpression, data: Nothing?): ConstantArgumentKind {
if (!booleanOperatorExpression.leftOperand.resolvedType.isBoolean || !booleanOperatorExpression.rightOperand.resolvedType.isBoolean) {
return ConstantArgumentKind.NOT_CONST
}
booleanOperatorExpression.leftOperand.accept(this, data).ifNotValidConst { return it }
booleanOperatorExpression.rightOperand.accept(this, data).ifNotValidConst { return it }
return ConstantArgumentKind.VALID_CONST
}
override fun visitGetClassCall(getClassCall: FirGetClassCall, data: Nothing?): ConstantArgumentKind {
var coneType = getClassCall.argument.getExpandedType()
if (coneType is ConeErrorType)
return ConstantArgumentKind.NOT_CONST
while (coneType.classId == StandardClassIds.Array)
coneType = (coneType.lowerBoundIfFlexible().typeArgumentsOfLowerBoundIfFlexible.first() as? ConeKotlinTypeProjection)?.type ?: break
val argument = getClassCall.argument
return when {
coneType is ConeTypeParameterType -> ConstantArgumentKind.KCLASS_LITERAL_OF_TYPE_PARAMETER_ERROR
argument is FirResolvedQualifier -> ConstantArgumentKind.VALID_CONST
argument is FirClassReferenceExpression -> ConstantArgumentKind.VALID_CONST
else -> ConstantArgumentKind.NOT_KCLASS_LITERAL
}
}
override fun visitVarargArgumentsExpression(
varargArgumentsExpression: FirVarargArgumentsExpression, data: Nothing?
): ConstantArgumentKind {
for (exp in varargArgumentsExpression.arguments) {
exp.accept(this, data).ifNotValidConst { return it }
}
return ConstantArgumentKind.VALID_CONST
}
override fun visitArrayLiteral(arrayLiteral: FirArrayLiteral, data: Nothing?): ConstantArgumentKind {
for (exp in arrayLiteral.arguments) {
exp.accept(this, data).ifNotValidConst { return it }
}
return ConstantArgumentKind.VALID_CONST
}
override fun visitThisReceiverExpression(thisReceiverExpression: FirThisReceiverExpression, data: Nothing?): ConstantArgumentKind {
val classSymbol = thisReceiverExpression.calleeReference.boundSymbol as? FirClassSymbol
return if (classSymbol?.classKind == ClassKind.OBJECT) {
ConstantArgumentKind.VALID_CONST
} else {
ConstantArgumentKind.NOT_CONST
}
}
override fun visitPropertyAccessExpression(
propertyAccessExpression: FirPropertyAccessExpression, data: Nothing?
): ConstantArgumentKind {
val propertySymbol = propertyAccessExpression.calleeReference.toResolvedCallableSymbol()
if (propertySymbol in propertyStack.get()) return ConstantArgumentKind.NOT_CONST
when (propertySymbol) {
// Null symbol means some error occurred.
// We use the same logic as in `visitErrorExpression`.
// Better to report "UNRESOLVED_REFERENCE" later than some "NOT_CONST" diagnostic right now.
null -> return ConstantArgumentKind.RESOLUTION_ERROR
is FirPropertySymbol -> {
val classKindOfParent = (propertySymbol.getReferencedClassSymbol() as? FirRegularClassSymbol)?.classKind
if (classKindOfParent == ClassKind.ENUM_CLASS) {
return ConstantArgumentKind.ENUM_NOT_CONST
}
val isConstWithoutInitializer = propertySymbol.unwrapFakeOverrides().canBeEvaluated()
|| propertySymbol.isCompileTimeBuiltinProperty()
when {
propertySymbol.isConst || isConstWithoutInitializer -> {
val receivers = listOf(propertyAccessExpression.dispatchReceiver, propertyAccessExpression.extensionReceiver)
if (receivers.count { it != null } == 2) {
return ConstantArgumentKind.NOT_CONST
}
receivers.singleOrNull { it != null }?.accept(this, data)?.ifNotValidConst { return it }
}
propertySymbol.isLocal -> return ConstantArgumentKind.NOT_CONST
propertyAccessExpression.getExpandedType().classId == StandardClassIds.KClass -> return ConstantArgumentKind.NOT_KCLASS_LITERAL
}
return when {
isConstWithoutInitializer -> ConstantArgumentKind.VALID_CONST
propertySymbol.isConst -> {
// even if called on CONSTANT_EVALUATION, it's safe to call resolvedInitializer, as intializers of const vals
// are resolved at previous IMPLICIT_TYPES_BODY_RESOLVE phase
val initializer = propertySymbol.resolvedInitializer
propertySymbol.visit { initializer?.accept(this, data) } ?: ConstantArgumentKind.RESOLUTION_ERROR
}
// if it called at checkers stage it's safe to call resolvedInitializer
// even if it will trigger BODY_RESOLVE phase, we don't violate phase contracts
calledOnCheckerStage -> when (propertySymbol.resolvedInitializer) {
is FirLiteralExpression -> when {
propertySymbol.isVal -> ConstantArgumentKind.NOT_CONST_VAL_IN_CONST_EXPRESSION
else -> ConstantArgumentKind.NOT_CONST
}
is FirGetClassCall -> ConstantArgumentKind.NOT_KCLASS_LITERAL
else -> ConstantArgumentKind.NOT_CONST
}
else -> ConstantArgumentKind.NOT_CONST
}
}
is FirFieldSymbol -> {
if (propertySymbol.isStatic && propertySymbol.modality == Modality.FINAL && propertySymbol.hasConstantInitializer) {
return ConstantArgumentKind.VALID_CONST
}
}
is FirEnumEntrySymbol -> return ConstantArgumentKind.VALID_CONST
}
return ConstantArgumentKind.NOT_CONST
}
override fun visitIntegerLiteralOperatorCall(
integerLiteralOperatorCall: FirIntegerLiteralOperatorCall, data: Nothing?
): ConstantArgumentKind {
return visitFunctionCall(integerLiteralOperatorCall, data)
}
override fun visitFunctionCall(functionCall: FirFunctionCall, data: Nothing?): ConstantArgumentKind {
val calleeReference = functionCall.calleeReference
if (calleeReference is FirErrorNamedReference || calleeReference is FirResolvedErrorReference) {
return ConstantArgumentKind.RESOLUTION_ERROR
}
if (functionCall.getExpandedType().classId == StandardClassIds.KClass) {
return ConstantArgumentKind.NOT_KCLASS_LITERAL
}
if (calleeReference !is FirResolvedNamedReference) return ConstantArgumentKind.NOT_CONST
return when (val symbol = calleeReference.resolvedSymbol) {
is FirNamedFunctionSymbol -> visitNamedFunction(functionCall, symbol)
is FirConstructorSymbol -> visitConstructorCall(functionCall, symbol)
else -> ConstantArgumentKind.NOT_CONST
}
}
private fun visitNamedFunction(functionCall: FirFunctionCall, symbol: FirNamedFunctionSymbol): ConstantArgumentKind {
if (!symbol.canBeEvaluated() && !functionCall.isCompileTimeBuiltinCall()) {
return ConstantArgumentKind.NOT_CONST
}
for (exp in functionCall.arguments.plus(functionCall.dispatchReceiver).plus(functionCall.extensionReceiver)) {
if (exp == null) continue
if (!exp.hasAllowedCompileTimeType()) return ConstantArgumentKind.NOT_CONST
exp.accept(this, null).ifNotValidConst { return it }
}
return ConstantArgumentKind.VALID_CONST
}
private fun visitConstructorCall(constructorCall: FirFunctionCall, symbol: FirConstructorSymbol): ConstantArgumentKind {
val classKindOfParent = (symbol.getReferencedClassSymbol() as? FirClassLikeSymbol<*>)?.fullyExpandedClass(session)?.classKind
return when {
classKindOfParent == ClassKind.ANNOTATION_CLASS -> ConstantArgumentKind.VALID_CONST
constructorCall.getExpandedType().isUnsignedType -> {
constructorCall.arguments.forEach { argumentExpression ->
argumentExpression.accept(this, null).ifNotValidConst { return it }
}
ConstantArgumentKind.VALID_CONST
}
else -> ConstantArgumentKind.NOT_CONST
}
}
override fun visitQualifiedAccessExpression(
qualifiedAccessExpression: FirQualifiedAccessExpression, data: Nothing?
): ConstantArgumentKind {
val expressionType = qualifiedAccessExpression.getExpandedType()
if (expressionType.isReflectFunctionType(session) || expressionType.isKProperty(session) || expressionType.isKMutableProperty(session)) {
return qualifiedAccessExpression.dispatchReceiver?.accept(this, data) ?: ConstantArgumentKind.VALID_CONST
}
return ConstantArgumentKind.VALID_CONST
}
override fun visitResolvedQualifier(resolvedQualifier: FirResolvedQualifier, data: Nothing?): ConstantArgumentKind {
return ConstantArgumentKind.VALID_CONST
}
override fun visitErrorResolvedQualifier(errorResolvedQualifier: FirErrorResolvedQualifier, data: Nothing?): ConstantArgumentKind {
return ConstantArgumentKind.VALID_CONST
}
override fun visitCallableReferenceAccess(callableReferenceAccess: FirCallableReferenceAccess, data: Nothing?): ConstantArgumentKind {
return visitQualifiedAccessExpression(callableReferenceAccess, data)
}
override fun visitEnumEntryDeserializedAccessExpression(
enumEntryDeserializedAccessExpression: FirEnumEntryDeserializedAccessExpression,
data: Nothing?,
): ConstantArgumentKind {
return ConstantArgumentKind.VALID_CONST
}
override fun visitClassReferenceExpression(
classReferenceExpression: FirClassReferenceExpression,
data: Nothing?,
): ConstantArgumentKind {
return ConstantArgumentKind.VALID_CONST
}
override fun visitAnnotationCall(annotationCall: FirAnnotationCall, data: Nothing?): ConstantArgumentKind {
return visitAnnotation(annotationCall, data)
}
override fun visitAnnotation(annotation: FirAnnotation, data: Nothing?): ConstantArgumentKind {
for (argument in annotation.argumentMapping.mapping.values) {
val argumentKind = argument.accept(this, data)
if (argumentKind != ConstantArgumentKind.VALID_CONST) return argumentKind
}
return ConstantArgumentKind.VALID_CONST
}
// --- Utils ---
private fun FirBasedSymbol<*>.canBeEvaluated(): Boolean {
return intrinsicConstEvaluation && this.hasAnnotation(StandardClassIds.Annotations.IntrinsicConstEvaluation, session)
}
private fun FirExpression.hasAllowedCompileTimeType(): Boolean {
val expClassId = resolvedType.unwrapToSimpleTypeUsingLowerBound().fullyExpandedType(session).classId
// TODO, KT-59823: add annotation for allowed constant types
return expClassId in StandardClassIds.constantAllowedTypes
}
private fun FirExpression.getExpandedType() = resolvedType.fullyExpandedType(session)
private fun FirFunctionCall.isCompileTimeBuiltinCall(): Boolean {
val calleeReference = this.calleeReference
if (calleeReference !is FirResolvedNamedReference) return false
val name = calleeReference.name
val symbol = calleeReference.resolvedSymbol as? FirCallableSymbol
if (!symbol.fromKotlin()) return false
val receiverClassId = this.dispatchReceiver?.getExpandedType()?.classId
if (receiverClassId in StandardClassIds.unsignedTypes) return false
if (
name in compileTimeFunctions ||
name in compileTimeExtensionFunctions ||
name == OperatorNameConventions.TO_STRING ||
name in OperatorNameConventions.NUMBER_CONVERSIONS
) return true
if (calleeReference.name == OperatorNameConventions.GET && receiverClassId == StandardClassIds.String) return true
return false
}
private fun FirPropertySymbol.isCompileTimeBuiltinProperty(): Boolean {
val receiverType = dispatchReceiverType ?: receiverParameter?.typeRef?.coneTypeSafe() ?: return false
val receiverClassId = receiverType.fullyExpandedType(session).classId ?: return false
return when (name.asString()) {
"length" -> receiverClassId == StandardClassIds.String
"code" -> receiverClassId == StandardClassIds.Char
else -> false
}
}
private fun FirCallableSymbol<*>?.fromKotlin(): Boolean {
return this?.callableId?.packageName?.asString() == "kotlin"
}
private fun FirCallableSymbol<*>?.getReferencedClassSymbol(): FirBasedSymbol<*>? =
this?.resolvedReturnTypeRef?.coneType?.toSymbol(session)
}