FIR: Fork flow for anonymous initializer

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt

@@ -915,7 +915,13 @@ abstract class FirDataFlowAnalyzer<FLOW : Flow>(
     // ----------------------------------- Init block -----------------------------------
 
     fun enterInitBlock(initBlock: FirAnonymousInitializer) {
-        graphBuilder.enterInitBlock(initBlock).mergeIncomingFlow()
+        graphBuilder.enterInitBlock(initBlock).let { (node, prevNode) ->
+            if (prevNode != null) {
+                node.flow = logicSystem.forkFlow(prevNode.flow)
+            } else {
+                node.mergeIncomingFlow()
+            }
+        }
     }
 
     fun exitInitBlock(initBlock: FirAnonymousInitializer) {

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

@@ -728,7 +728,8 @@ class ControlFlowGraphBuilder {
 
     // ----------------------------------- Block -----------------------------------
 
-    fun enterInitBlock(initBlock: FirAnonymousInitializer): InitBlockEnterNode {
+    fun enterInitBlock(initBlock: FirAnonymousInitializer): Pair<InitBlockEnterNode, CFGNode<*>?> {
+        val lastNode = lastNodes.topOrNull()
         graphs.push(ControlFlowGraph(initBlock, "init block", ControlFlowGraph.Kind.ClassInitializer))
         val enterNode = createInitBlockEnterNode(initBlock).also {
             lexicalScopes.push(stackOf(it))
@@ -737,7 +738,7 @@ class ControlFlowGraphBuilder {
         initBlockExitNodes.push(exitNode)
         exitNodes.push(exitNode)
         levelCounter++
-        return enterNode
+        return enterNode to lastNode
     }
 
     fun exitInitBlock(initBlock: FirAnonymousInitializer): InitBlockExitNode {