[FIR] Hide modifications of CFG from public API

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/cfg/ControlFlowGraph.kt

@@ -3,6 +3,8 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
+@file:Suppress("Reformat")
+
 package org.jetbrains.kotlin.fir.resolve.dfa.cfg
 
 import org.jetbrains.kotlin.fir.FirElement
@@ -15,9 +17,18 @@ import org.jetbrains.kotlin.fir.visitors.FirTransformer
 import org.jetbrains.kotlin.fir.visitors.FirVisitor
 
 class ControlFlowGraph(val name: String, val kind: Kind) {
-    val nodes = mutableListOf<CFGNode<*>>()
+    private val _nodes: MutableList<CFGNode<*>> = mutableListOf()
+
+    val nodes: List<CFGNode<*>> get() = _nodes
+
+    internal fun addNode(node: CFGNode<*>) {
+        _nodes += node
+    }
+
     lateinit var enterNode: CFGNode<*>
+        internal set
     lateinit var exitNode: CFGNode<*>
+        internal set
 
     enum class Kind {
         Function, ClassInitializer, PropertyInitializer, TopLevel
@@ -30,12 +41,12 @@ enum class EdgeKind {
 
 sealed class CFGNode<out E : FirElement>(val owner: ControlFlowGraph, val level: Int, private val id: Int) {
     companion object {
-        fun addEdge(from: CFGNode<*>, to: CFGNode<*>, kind: EdgeKind, propagateDeadness: Boolean) {
-            from.followingNodes += to
-            to.previousNodes += from
+        internal fun addEdge(from: CFGNode<*>, to: CFGNode<*>, kind: EdgeKind, propagateDeadness: Boolean) {
+            from._followingNodes += to
+            to._previousNodes += from
             if (kind != EdgeKind.Simple) {
-                from.outgoingEdges[to] = kind
-                to.incomingEdges[from] = kind
+                from._outgoingEdges[to] = kind
+                to._incomingEdges[from] = kind
             }
             if (propagateDeadness && kind == EdgeKind.Dead) {
                 to.isDead = true
@@ -44,19 +55,29 @@ sealed class CFGNode<out E : FirElement>(val owner: ControlFlowGraph, val level:
     }
 
     init {
-        owner.nodes += this
+        @Suppress("LeakingThis")
+        owner.addNode(this)
     }
 
-    val previousNodes: MutableList<CFGNode<*>> = mutableListOf()
-    val followingNodes: MutableList<CFGNode<*>> = mutableListOf()
+    private val _previousNodes: MutableList<CFGNode<*>> = mutableListOf()
+    private val _followingNodes: MutableList<CFGNode<*>> = mutableListOf()
 
-    val incomingEdges = mutableMapOf<CFGNode<*>, EdgeKind>().withDefault { EdgeKind.Simple }
-    val outgoingEdges = mutableMapOf<CFGNode<*>, EdgeKind>().withDefault { EdgeKind.Simple }
+    val previousNodes: List<CFGNode<*>> get() = _previousNodes
+    val followingNodes: List<CFGNode<*>> get() = _followingNodes
 
-    val firstPreviousNode: CFGNode<*> get() = previousNodes.first()
+    private val _incomingEdges = mutableMapOf<CFGNode<*>, EdgeKind>().withDefault { EdgeKind.Simple }
+    private val _outgoingEdges = mutableMapOf<CFGNode<*>, EdgeKind>().withDefault { EdgeKind.Simple }
+
+    val incomingEdges: Map<CFGNode<*>, EdgeKind> get() = _incomingEdges
+    val outgoingEdges: Map<CFGNode<*>, EdgeKind> get() = _outgoingEdges
 
     abstract val fir: E
     var isDead: Boolean = false
+        protected set
+
+    internal fun updateDeadStatus() {
+        isDead = incomingEdges.size == previousNodes.size && incomingEdges.values.all { it == EdgeKind.Dead }
+    }
 
     final override fun equals(other: Any?): Boolean {
         if (other !is CFGNode<*>) return false
@@ -68,6 +89,8 @@ sealed class CFGNode<out E : FirElement>(val owner: ControlFlowGraph, val level:
     }
 }
 
+val CFGNode<*>.firstPreviousNode: CFGNode<*> get() = previousNodes.first()
+
 interface EnterNode
 interface ExitNode
 

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/cfg/ControlFlowGraphBuilder.kt

@@ -131,7 +131,7 @@ class ControlFlowGraphBuilder {
             }
             lexicalScopes.pop()
         }
-        exitNode.markAsDeadIfNecessary()
+        exitNode.updateDeadStatus()
         val graph = if (!isInplace) {
             graphs.pop()
         } else {
@@ -175,7 +175,7 @@ class ControlFlowGraphBuilder {
             functionExitNodes.top().also {
                 addEdge(lastNodes.pop(), it)
                 lastNodes.push(it)
-                it.markAsDeadIfNecessary()
+                it.updateDeadStatus()
             }
         } else {
             levelCounter--
@@ -201,7 +201,7 @@ class ControlFlowGraphBuilder {
     fun exitProperty(property: FirProperty): Pair<PropertyInitializerExitNode, ControlFlowGraph> {
         val topLevelVariableExitNode = topLevelVariableInitializerExitNodes.pop().also {
             addNewSimpleNode(it)
-            it.markAsDeadIfNecessary()
+            it.updateDeadStatus()
         }
         levelCounter--
         exitNodes.pop()
@@ -285,7 +285,7 @@ class ControlFlowGraphBuilder {
                 addEdge(this, whenExitNode)
             }
         } else null
-        whenExitNode.markAsDeadIfNecessary()
+        whenExitNode.updateDeadStatus()
         lastNodes.push(whenExitNode)
         levelCounter--
         return whenExitNode to syntheticElseBranchNode
@@ -332,7 +332,7 @@ class ControlFlowGraphBuilder {
             addEdge(loopBlockExitNode, conditionEnterNode, propagateDeadness = false)
         }
         val loopExitNode = loopExitNodes.pop()
-        loopExitNode.markAsDeadIfNecessary()
+        loopExitNode.updateDeadStatus()
         lastNodes.push(loopExitNode)
         levelCounter--
         return loopBlockExitNode to loopExitNode
@@ -373,7 +373,7 @@ class ControlFlowGraphBuilder {
         addEdge(conditionExitNode, blockEnterNode, propagateDeadness = false, isDead = conditionBooleanValue == false)
         val loopExit = loopExitNodes.pop()
         addEdge(conditionExitNode, loopExit, propagateDeadness = false, isDead = conditionBooleanValue == true)
-        loopExit.markAsDeadIfNecessary()
+        loopExit.updateDeadStatus()
         lastNodes.push(loopExit)
         levelCounter--
         return conditionExitNode to loopExit
@@ -410,7 +410,7 @@ class ControlFlowGraphBuilder {
         return binaryAndExitNodes.pop().also {
             val rightNode = lastNodes.pop()
             addEdge(rightNode, it, propagateDeadness = false, isDead = it.leftOperandNode.booleanConstValue == false)
-            it.markAsDeadIfNecessary()
+            it.updateDeadStatus()
             lastNodes.push(it)
         }
     }
@@ -456,7 +456,7 @@ class ControlFlowGraphBuilder {
         return binaryOrExitNodes.pop().also {
             val rightNode = lastNodes.pop()
             addEdge(rightNode, it, propagateDeadness = false)
-            it.markAsDeadIfNecessary()
+            it.updateDeadStatus()
             lastNodes.push(it)
         }
     }
@@ -531,7 +531,7 @@ class ControlFlowGraphBuilder {
         levelCounter--
         catchNodeStorages.pop()
         val node = tryExitNodes.pop()
-        node.markAsDeadIfNecessary()
+        node.updateDeadStatus()
         lastNodes.push(node)
         return node
     }
@@ -616,7 +616,7 @@ class ControlFlowGraphBuilder {
         levelCounter--
         return initBlockExitNodes.pop().also {
             addNewSimpleNode(it)
-            it.markAsDeadIfNecessary()
+            it.updateDeadStatus()
             lexicalScopes.pop()
             exitNodes.pop()
             graphs.pop()
@@ -639,16 +639,12 @@ class ControlFlowGraphBuilder {
     fun exitSafeCall(qualifiedAccess: FirQualifiedAccess): ExitSafeCallNode {
         return exitSafeCallNodes.pop().also {
             addNewSimpleNode(it)
-            it.markAsDeadIfNecessary()
+            it.updateDeadStatus()
         }
     }
 
     // -------------------------------------------------------------------------------------------------------------------------
 
-    private fun CFGNode<*>.markAsDeadIfNecessary() {
-        isDead = incomingEdges.size == previousNodes.size && incomingEdges.values.all { it == EdgeKind.Dead }
-    }
-
     private fun addNodeThatReturnsNothing(node: CFGNode<*>) {
         /*
          * `return` is temporary solution that is needed for init block