FIR CFG: merge DFA + CFA edge in Simple edge

compiler/fir/analysis-tests/testData/resolve/cfg/flowFromInplaceLambda.dot

@@ -310,14 +310,14 @@ digraph flowFromInplaceLambda_kt {
         106 [label="Exit function test_4" style="filled" fillcolor=red];
     }
     105 -> {107};
-    107 -> {108} [color=green];
+    107 -> {108};
     107 -> {126} [color=red];
     108 -> {109};
     109 -> {110};
     110 -> {111};
     111 -> {112};
     112 -> {113};
-    113 -> {114} [color=green];
+    113 -> {114};
     113 -> {132} [color=red];
     114 -> {115};
     115 -> {116};
@@ -419,7 +419,7 @@ digraph flowFromInplaceLambda_kt {
         159 [label="Exit function test_6" style="filled" fillcolor=red];
     }
     158 -> {160};
-    160 -> {161} [color=green];
+    160 -> {161};
     160 -> {165} [color=red];
     161 -> {162};
     162 -> {163};

compiler/fir/analysis-tests/testData/resolve/cfg/lambdaAsReturnOfLambda.dot

@@ -39,7 +39,7 @@ digraph lambdaAsReturnOfLambda_kt {
         11 [label="Exit property" style="filled" fillcolor=red];
     }
     10 -> {12};
-    12 -> {13} [color=green];
+    12 -> {13};
     12 -> {0} [color=red];
     13 -> {14};
     14 -> {15};

compiler/fir/analysis-tests/testData/resolve/cfg/lambdaReturningObject.dot

@@ -72,7 +72,7 @@ digraph lambdaReturningObject_kt {
         18 [label="Exit function foo" style="filled" fillcolor=red];
     }
     17 -> {19};
-    19 -> {20} [color=green];
+    19 -> {20};
     19 -> {23} [color=red];
     20 -> {21};
     21 -> {22};

compiler/fir/analysis-tests/testData/resolve/cfg/postponedLambdaInConstructor.dot

@@ -54,7 +54,7 @@ digraph postponedLambdaInConstructor_kt {
     13 -> {15};
     14 -> {9} [color=green];
     14 -> {12} [color=red];
-    15 -> {16} [color=green];
+    15 -> {16};
     15 -> {17} [color=red];
     16 -> {14};
     17 -> {19};

compiler/fir/analysis-tests/testData/resolve/smartcasts/controlStructures/returns.dot

@@ -477,7 +477,7 @@ digraph returns_kt {
     166 -> {167};
     167 -> {145};
     168 -> {169};
-    169 -> {170} [color=green];
+    169 -> {170};
     169 -> {172} [color=red];
     170 -> {171};
     171 -> {140};

compiler/fir/analysis-tests/testData/resolve/smartcasts/safeCalls/safeCalls.dot

@@ -142,7 +142,7 @@ digraph safeCalls_kt {
     47 -> {44};
     48 -> {50};
     49 -> {53};
-    50 -> {51} [color=green];
+    50 -> {51};
     50 -> {55} [color=red];
     51 -> {52};
     52 -> {49};

compiler/fir/analysis-tests/testData/resolveWithStdlib/contracts/fromLibrary/callsInPlace.dot

@@ -274,7 +274,7 @@ digraph callsInPlace_kt {
         93 [label="Exit function test_8" style="filled" fillcolor=red];
     }
     92 -> {94};
-    94 -> {95} [color=green];
+    94 -> {95};
     94 -> {97} [color=red];
     95 -> {96};
     96 -> {93};

compiler/fir/analysis-tests/testData/resolveWithStdlib/delegates/delegateWithAnonymousObject.dot

@@ -163,14 +163,14 @@ digraph delegateWithAnonymousObject_kt {
     66 -> {54} [color=green];
     54 -> {56};
     55 -> {67} [color=green];
-    56 -> {57} [color=green];
+    56 -> {57};
     57 -> {58};
     58 -> {59};
     59 -> {60};
     60 -> {61};
     61 -> {62};
     62 -> {63};
-    63 -> {64} [color=green];
+    63 -> {64};
     63 -> {21} [color=red];
     64 -> {65};
     65 -> {55};

compiler/fir/analysis-tests/testData/resolveWithStdlib/smartcasts/tryWithLambdaInside.dot

@@ -155,7 +155,7 @@ finally {
     33 -> {41};
     34 -> {35};
     35 -> {36};
-    36 -> {37} [color=green];
+    36 -> {37};
     36 -> {46} [color=red];
     37 -> {38};
     38 -> {39};

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

@@ -71,10 +71,23 @@ sealed class CFGNode<out E : FirElement>(val owner: ControlFlowGraph, val level:
             addJustKindEdge(from, to, kind, propagateDeadness)
         }
 
+        private fun merge(first: EdgeKind, second: EdgeKind?): EdgeKind? {
+            return when (first) {
+                second -> first
+                EdgeKind.Cfg -> if (second == EdgeKind.Dfg) null else first
+                EdgeKind.Dfg -> if (second == EdgeKind.Cfg) null else first
+                else -> first
+            }
+        }
+
         internal fun addJustKindEdge(from: CFGNode<*>, to: CFGNode<*>, kind: EdgeKind, propagateDeadness: Boolean) {
             if (kind != EdgeKind.Simple) {
-                from._outgoingEdges[to] = kind
+                merge(kind, from._outgoingEdges[to])?.let {
-                to._incomingEdges[from] = kind
+                    from._outgoingEdges[to] = it
+                } ?: from._outgoingEdges.remove(to)
+                merge(kind, to._incomingEdges[from])?.let {
+                    to._incomingEdges[from] = it
+                } ?: to._incomingEdges.remove(from)
             }
             if (propagateDeadness && kind == EdgeKind.Dead) {
                 to.isDead = true