[FIR] Update smartcast tests

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

@@ -312,4 +312,99 @@ digraph smartcastToNothing_kt {
     106 -> {95} [color=red];
     106 -> {96} [color=green];
 
+    subgraph cluster_26 {
+        color=red
+        107 [label="Enter function test_1" style="filled" fillcolor=red];
+        subgraph cluster_27 {
+            color=blue
+            108 [label="Enter block"];
+            subgraph cluster_28 {
+                color=blue
+                109 [label="Enter when"];
+                subgraph cluster_29 {
+                    color=blue
+                    110 [label="Enter when branch condition "];
+                    111 [label="Access variable R|<local>/a|"];
+                    112 [label="Type operator: (R|<local>/a| is R|kotlin/Nothing?|)"];
+                    113 [label="Exit when branch condition"];
+                }
+                114 [label="Synthetic else branch"];
+                115 [label="Enter when branch result"];
+                subgraph cluster_30 {
+                    color=blue
+                    116 [label="Enter block"];
+                    117 [label="Access variable R|<local>/a|"];
+                    118 [label="Enter safe call"];
+                    119 [label="Access variable R|kotlin/String.length|"];
+                    120 [label="Exit safe call"];
+                    121 [label="Variable declaration: lval b: R|kotlin/Int?|"];
+                    122 [label="Exit block"];
+                }
+                123 [label="Exit when branch result"];
+                124 [label="Exit when"];
+            }
+            subgraph cluster_31 {
+                color=blue
+                125 [label="Enter when"];
+                subgraph cluster_32 {
+                    color=blue
+                    126 [label="Enter when branch condition "];
+                    127 [label="Access variable R|<local>/a|"];
+                    128 [label="Type operator: (R|<local>/a| is R|kotlin/Nothing|)"];
+                    129 [label="Exit when branch condition"];
+                }
+                130 [label="Synthetic else branch"];
+                131 [label="Enter when branch result"];
+                subgraph cluster_33 {
+                    color=blue
+                    132 [label="Enter block"];
+                    133 [label="Access variable R|<local>/a|"];
+                    134 [label="Stub" style="filled" fillcolor=gray];
+                    135 [label="Access variable R|kotlin/String.length|" style="filled" fillcolor=gray];
+                    136 [label="Variable declaration: lval b: R|kotlin/Int|" style="filled" fillcolor=gray];
+                    137 [label="Exit block" style="filled" fillcolor=gray];
+                }
+                138 [label="Exit when branch result" style="filled" fillcolor=gray];
+                139 [label="Exit when"];
+            }
+            140 [label="Exit block"];
+        }
+        141 [label="Exit function test_1" style="filled" fillcolor=red];
+    }
+    107 -> {108};
+    108 -> {109};
+    109 -> {110};
+    110 -> {111};
+    111 -> {112};
+    112 -> {113};
+    113 -> {115 114};
+    114 -> {124};
+    115 -> {116};
+    116 -> {117};
+    117 -> {118 120};
+    118 -> {119};
+    119 -> {120};
+    120 -> {121};
+    121 -> {122};
+    122 -> {123};
+    123 -> {124};
+    124 -> {125};
+    125 -> {126};
+    126 -> {127};
+    127 -> {128};
+    128 -> {129};
+    129 -> {131 130};
+    130 -> {139};
+    131 -> {132};
+    132 -> {133};
+    133 -> {141}    [label=onUncaughtException];
+    133 -> {134} [style=dotted];
+    134 -> {135} [style=dotted];
+    135 -> {136} [style=dotted];
+    136 -> {137} [style=dotted];
+    137 -> {138} [style=dotted];
+    138 -> {139} [style=dotted];
+    139 -> {140};
+    140 -> {141};
+
 }

compiler/fir/analysis-tests/testData/resolve/smartcasts/smartcastToNothing.fir.txt

@@ -50,3 +50,17 @@ FILE: smartcastToNothing.kt
         }
         ) }
     }
+    public final fun test_1(a: R|kotlin/String?|): R|kotlin/Unit| {
+        when () {
+            (R|<local>/a| is R|kotlin/Nothing?|) ->  {
+                lval b: R|kotlin/Int?| = R|<local>/a|?.{ $subj$.R|kotlin/String.length| }
+            }
+        }
+
+        when () {
+            (R|<local>/a| is R|kotlin/Nothing|) ->  {
+                lval b: R|kotlin/Int| = R|<local>/a|.R|kotlin/String.length|
+            }
+        }
+
+    }

compiler/fir/analysis-tests/testData/resolve/smartcasts/smartcastToNothing.kt

@@ -22,3 +22,13 @@ fun test_0(results: List<Nothing>) {
     }
     s?.let { it.a }
 }
+
+fun test_1(a: String?) {
+    if (a is Nothing?) {
+        val b = a?.length
+    }
+
+    if (a is Nothing) {
+        val b = a.length
+    }
+}