FIR CFG: create TryMainBlockExitNode before visiting try main block

so that a node that returns Nothing inside try main block can route to
the exit of try main block, instead of exit target for try directly.

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

@@ -718,8 +718,8 @@ abstract class FirDataFlowAnalyzer<FLOW : Flow>(
         tryMainBlockEnterNode.mergeIncomingFlow(shouldForkFlow = true)
     }
 
-    fun exitTryMainBlock(tryExpression: FirTryExpression) {
-        graphBuilder.exitTryMainBlock(tryExpression).mergeIncomingFlow()
+    fun exitTryMainBlock() {
+        graphBuilder.exitTryMainBlock().mergeIncomingFlow()
     }
 
     fun enterCatchClause(catch: FirCatch) {

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

@@ -832,6 +832,9 @@ class ControlFlowGraphBuilder {
         val enterTryNodeBlock = createTryMainBlockEnterNode(tryExpression)
         addNewSimpleNode(enterTryNodeBlock)
 
+        val exitTryNodeBlock = createTryMainBlockExitNode(tryExpression)
+        tryMainExitNodes.push(exitTryNodeBlock)
+
         for (catch in tryExpression.catches) {
             val catchNode = createCatchClauseEnterNode(catch)
             catchNodeStorage.push(catchNode)
@@ -850,10 +853,9 @@ class ControlFlowGraphBuilder {
         return enterTryExpressionNode to enterTryNodeBlock
     }
 
-    fun exitTryMainBlock(tryExpression: FirTryExpression): TryMainBlockExitNode {
+    fun exitTryMainBlock(): TryMainBlockExitNode {
         levelCounter--
-        val node = createTryMainBlockExitNode(tryExpression)
-        tryMainExitNodes.push(node)
+        val node = tryMainExitNodes.top()
         popAndAddEdge(node)
         val finallyEnterNode = finallyEnterNodes.topOrNull()
         // NB: Check the level to avoid adding an edge to the finally block at an upper level.
@@ -1266,7 +1268,7 @@ class ControlFlowGraphBuilder {
             tryExitNodes.top().fir.finallyBlock == null -> {
                 // (3)... without finally ...(4)
                 // Either in try-main or catch.
-                if (tryExitNodes.size == tryMainExitNodes.size) {
+                if (tryMainExitNodes.top().followingNodes.isNotEmpty()) {
                     // (4)... in catch, i.e., re-throw.
                     exitTargetsForTry.top()
                 } else {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirControlFlowStatementsResolveTransformer.kt

@@ -144,7 +144,7 @@ class FirControlFlowStatementsResolveTransformer(transformer: FirBodyResolveTran
         tryExpression.transformAnnotations(transformer, ResolutionMode.ContextIndependent)
         dataFlowAnalyzer.enterTryExpression(tryExpression)
         tryExpression.transformTryBlock(transformer, ResolutionMode.ContextDependent)
-        dataFlowAnalyzer.exitTryMainBlock(tryExpression)
+        dataFlowAnalyzer.exitTryMainBlock()
         tryExpression.transformCatches(this, ResolutionMode.ContextDependent)
 
         var callCompleted = false