org.jetbrains.kotlin.fir.analysis.checkers.declaration.FirTailrecFunctionChecker.kt Maven / Gradle / Ivy
/*
* Copyright 2010-2021 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.analysis.checkers.declaration
import org.jetbrains.kotlin.descriptors.Visibilities
import org.jetbrains.kotlin.fir.analysis.cfa.util.TraverseDirection
import org.jetbrains.kotlin.fir.analysis.cfa.util.traverse
import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
import org.jetbrains.kotlin.diagnostics.reportOn
import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
import org.jetbrains.kotlin.fir.declarations.utils.isOverride
import org.jetbrains.kotlin.fir.declarations.utils.isTailRec
import org.jetbrains.kotlin.fir.declarations.utils.visibility
import org.jetbrains.kotlin.fir.expressions.FirThisReceiverExpression
import org.jetbrains.kotlin.fir.expressions.arguments
import org.jetbrains.kotlin.fir.expressions.impl.FirNoReceiverExpression
import org.jetbrains.kotlin.fir.expressions.toResolvedCallableSymbol
import org.jetbrains.kotlin.fir.resolve.dfa.cfg.*
import org.jetbrains.kotlin.fir.resolve.dfa.controlFlowGraph
import org.jetbrains.kotlin.fir.symbols.impl.FirClassSymbol
import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
import org.jetbrains.kotlin.fir.types.toSymbol
object FirTailrecFunctionChecker : FirSimpleFunctionChecker() {
override fun check(declaration: FirSimpleFunction, context: CheckerContext, reporter: DiagnosticReporter) {
if (!declaration.isTailRec) return
if (!(declaration.isEffectivelyFinal(context) || declaration.visibility == Visibilities.Private)) {
reporter.reportOn(declaration.source, FirErrors.TAILREC_ON_VIRTUAL_MEMBER_ERROR, context)
}
val graph = declaration.controlFlowGraphReference?.controlFlowGraph ?: return
var tryScopeCount = 0
var catchScopeCount = 0
var finallyScopeCount = 0
var tailrecCount = 0
graph.traverse(TraverseDirection.Forward, object : ControlFlowGraphVisitorVoid() {
override fun visitNode(node: CFGNode<*>) {}
override fun visitTryMainBlockEnterNode(node: TryMainBlockEnterNode) {
tryScopeCount++
}
override fun visitTryMainBlockExitNode(node: TryMainBlockExitNode) {
tryScopeCount--
}
override fun visitCatchClauseEnterNode(node: CatchClauseEnterNode) {
catchScopeCount++
}
override fun visitCatchClauseExitNode(node: CatchClauseExitNode) {
catchScopeCount--
}
override fun visitFinallyBlockEnterNode(node: FinallyBlockEnterNode) {
finallyScopeCount++
}
override fun visitFinallyBlockExitNode(node: FinallyBlockExitNode) {
finallyScopeCount--
}
override fun visitFunctionCallNode(node: FunctionCallNode) {
val functionCall = node.fir
val resolvedSymbol = functionCall.calleeReference.toResolvedCallableSymbol() as? FirNamedFunctionSymbol ?: return
if (resolvedSymbol != declaration.symbol) return
if (functionCall.arguments.size != resolvedSymbol.valueParameterSymbols.size && resolvedSymbol.isOverride) {
// Overridden functions using default arguments at tail call are not included: KT-4285
reporter.reportOn(functionCall.source, FirErrors.NON_TAIL_RECURSIVE_CALL, context)
return
}
val dispatchReceiver = functionCall.dispatchReceiver
val dispatchReceiverOwner = declaration.dispatchReceiverType?.toSymbol(context.session) as? FirClassSymbol<*>
val sameReceiver = dispatchReceiver is FirNoReceiverExpression ||
(dispatchReceiver is FirThisReceiverExpression && dispatchReceiver.calleeReference.boundSymbol == dispatchReceiverOwner) ||
dispatchReceiverOwner?.classKind?.isSingleton == true
if (!sameReceiver) {
// A call on a different receiver might get dispatched to a different method, so it can't be optimized.
reporter.reportOn(functionCall.source, FirErrors.NON_TAIL_RECURSIVE_CALL, context)
} else if (tryScopeCount > 0 || catchScopeCount > 0 || finallyScopeCount > 0) {
reporter.reportOn(functionCall.source, FirErrors.TAIL_RECURSION_IN_TRY_IS_NOT_SUPPORTED, context)
} else if (node.hasMoreFollowingInstructions(declaration)) {
reporter.reportOn(functionCall.source, FirErrors.NON_TAIL_RECURSIVE_CALL, context)
} else if (!node.isDead) {
tailrecCount++
}
}
})
if (tailrecCount == 0) {
reporter.reportOn(declaration.source, FirErrors.NO_TAIL_CALLS_FOUND, context)
}
}
private fun CFGNode<*>.hasMoreFollowingInstructions(tailrecFunction: FirSimpleFunction): Boolean {
for (next in followingNodes) {
val edge = outgoingEdges.getValue(next)
if (!edge.kind.usedInCfa || edge.kind.isDead) continue
if (edge.kind.isBack) return true
val hasMore = when (next) {
// If exiting another function, then it means this call is inside a nested local function, in which case, it's not a tailrec call.
is FunctionExitNode -> return next.fir != tailrecFunction
is JumpNode, is BinaryAndExitNode, is BinaryOrExitNode, is WhenBranchResultExitNode, is WhenExitNode, is BlockExitNode ->
next.hasMoreFollowingInstructions(tailrecFunction)
else -> return true
}
if (hasMore) return hasMore
}
return false
}
}