FIR CFA: remove infinite loops from toposort

Finally, no more tests getting stuck on `orderNodes`. Only took me what,
75 commits to fix enough things to make this actually work?

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

@@ -73,11 +73,6 @@ class ControlFlowGraphBuilder {
 
     private val notCompletedFunctionCalls: Stack<MutableList<FunctionCallNode>> = stackOf()
 
-    // ----------------------------------- API for node builders -----------------------------------
-
-    private var idCounter: Int = Random.nextInt()
-    fun createId(): Int = idCounter++
-
     // ----------------------------------- Public API -----------------------------------
 
     fun returnExpressionsOfAnonymousFunction(function: FirAnonymousFunction): Collection<FirExpression>? {
@@ -130,7 +125,6 @@ class ControlFlowGraphBuilder {
 
     private fun popGraph(): ControlFlowGraph {
         levelCounter--
-        // TODO: count nodes per graph, validate the list after sorting
         return graphs.pop().also { it.complete() }
     }
 

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

@@ -9,6 +9,9 @@ import org.jetbrains.kotlin.fir.FirElement
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.expressions.*
 
+@OptIn(CfgInternals::class)
+private fun ControlFlowGraphBuilder.createId(): Int = currentGraph.nodeCount++
+
 fun ControlFlowGraphBuilder.createStubNode(): StubNode = StubNode(currentGraph, levelCounter, createId())
 
 fun ControlFlowGraphBuilder.createFakeExpressionEnterNode(): FakeExpressionEnterNode =