diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzerImpl.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzerImpl.kt
index a456a93c506..1e8b1b82ee5 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzerImpl.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzerImpl.kt
@@ -101,11 +101,19 @@ class FirDataFlowAnalyzerImpl(transformer: FirBodyResolveTransformer) : FirDataF
 
     // ----------------------------------- Operator call -----------------------------------
 
+    private fun FirExpression.getResolvedSymbol(): FirCallableSymbol<*>? {
+        val expression = (this as? FirWhenSubjectExpression)?.whenSubject?.whenExpression?.let {
+            it.subjectVariable?.symbol?.let { return it }
+            it.subject
+        } ?: this
+        return expression.toResolvedCallableSymbol() as? FirCallableSymbol<*>
+    }
+
     override fun exitTypeOperatorCall(typeOperatorCall: FirTypeOperatorCall) {
         val node = graphBuilder.exitTypeOperatorCall(typeOperatorCall).passFlow(false)
         try {
             if (typeOperatorCall.operation !in FirOperation.TYPES) return
-            val symbol: FirCallableSymbol<*> = typeOperatorCall.argument.toResolvedCallableSymbol() as? FirCallableSymbol<*> ?: return
+            val symbol: FirCallableSymbol<*> = typeOperatorCall.argument.getResolvedSymbol() ?: return
             val type = typeOperatorCall.conversionTypeRef.coneTypeSafe<ConeKotlinType>() ?: return
             val varVariable = getRealVariable(symbol)
 
diff --git a/compiler/fir/resolve/testData/resolve/smartcasts/when.cfg.dot b/compiler/fir/resolve/testData/resolve/smartcasts/when.cfg.dot
new file mode 100644
index 00000000000..e5c6a9d4804
--- /dev/null
+++ b/compiler/fir/resolve/testData/resolve/smartcasts/when.cfg.dot
@@ -0,0 +1,514 @@
+digraph when_kt {
+subgraph foo {
+  0 [shape=box label="Enter function foo"];
+  1 [shape=box label="Exit function foo"];
+
+  0 -> {1};
+}
+
+subgraph bar {
+  2 [shape=box label="Enter function bar"];
+  3 [shape=box label="Exit function bar"];
+
+  2 -> {3};
+}
+
+subgraph test_1 {
+  4 [shape=box label="Enter function test_1"];
+  5 [shape=box label="Enter block"];
+  6 [shape=box label="Enter when"];
+  7 [shape=box label="Enter when branch condition "];
+  8 [shape=box label="Access variable R|<local>/x|"];
+  9 [shape=box label="Type operator: x is A"];
+  10 [shape=box label="Exit when branch condition"];
+  11 [shape=box label="Enter block"];
+  12 [shape=box label="Access variable R|<local>/x|"];
+  13 [shape=box label="Function call: R|<local>/x|.R|/A.foo|()"];
+  14 [shape=box label="Exit block"];
+  15 [shape=box label="Exit when branch result"];
+  16 [shape=box label="Enter when branch condition "];
+  17 [shape=box label="Access variable R|<local>/x|"];
+  18 [shape=box label="Type operator: x is B"];
+  19 [shape=box label="Exit when branch condition"];
+  20 [shape=box label="Enter block"];
+  21 [shape=box label="Access variable R|<local>/x|"];
+  22 [shape=box label="Function call: R|<local>/x|.R|/B.bar|()"];
+  23 [shape=box label="Exit block"];
+  24 [shape=box label="Exit when branch result"];
+  25 [shape=box label="Enter when branch condition else"];
+  26 [shape=box label="Exit when branch condition"];
+  27 [shape=box label="Enter block"];
+  28 [shape=box label="Exit block"];
+  29 [shape=box label="Exit when branch result"];
+  30 [shape=box label="Exit when"];
+  31 [shape=box label="Enter when"];
+  32 [shape=box label="Enter when branch condition "];
+  33 [shape=box label="Access variable R|<local>/x|"];
+  34 [shape=box label="Type operator: x !is A"];
+  35 [shape=box label="Exit when branch condition"];
+  36 [shape=box label="Enter block"];
+  37 [shape=box label="Exit block"];
+  38 [shape=box label="Exit when branch result"];
+  39 [shape=box label="Enter when branch condition "];
+  40 [shape=box label="Access variable R|<local>/x|"];
+  41 [shape=box label="Type operator: x !is B"];
+  42 [shape=box label="Exit when branch condition"];
+  43 [shape=box label="Enter block"];
+  44 [shape=box label="Access variable R|<local>/x|"];
+  45 [shape=box label="Function call: R|<local>/x|.R|/A.foo|()"];
+  46 [shape=box label="Exit block"];
+  47 [shape=box label="Exit when branch result"];
+  48 [shape=box label="Enter when branch condition "];
+  49 [shape=box label="Access variable R|<local>/x|"];
+  50 [shape=box label="Type operator: x is Int"];
+  51 [shape=box label="Exit when branch condition"];
+  52 [shape=box label="Enter block"];
+  53 [shape=box label="Access variable R|<local>/x|"];
+  54 [shape=box label="Function call: R|<local>/x|.R|/A.foo|()"];
+  55 [shape=box label="Access variable R|<local>/x|"];
+  56 [shape=box label="Function call: R|<local>/x|.R|/B.bar|()"];
+  57 [shape=box label="Access variable R|<local>/x|"];
+  58 [shape=box label="Function call: R|<local>/x|.R|kotlin/Int.inc|()"];
+  59 [shape=box label="Exit block"];
+  60 [shape=box label="Exit when branch result"];
+  61 [shape=box label="Enter when branch condition else"];
+  62 [shape=box label="Exit when branch condition"];
+  63 [shape=box label="Enter block"];
+  64 [shape=box label="Access variable R|<local>/x|"];
+  65 [shape=box label="Function call: R|<local>/x|.R|/A.foo|()"];
+  66 [shape=box label="Access variable R|<local>/x|"];
+  67 [shape=box label="Function call: R|<local>/x|.R|/B.bar|()"];
+  68 [shape=box label="Exit block"];
+  69 [shape=box label="Exit when branch result"];
+  70 [shape=box label="Exit when"];
+  71 [shape=box label="Exit block"];
+  72 [shape=box label="Exit function test_1"];
+
+  4 -> {5};
+  5 -> {6};
+  6 -> {7};
+  7 -> {8};
+  8 -> {9};
+  9 -> {10};
+  10 -> {11 16};
+  11 -> {12};
+  12 -> {13};
+  13 -> {14};
+  14 -> {15};
+  15 -> {30};
+  16 -> {17};
+  17 -> {18};
+  18 -> {19};
+  19 -> {20 25};
+  20 -> {21};
+  21 -> {22};
+  22 -> {23};
+  23 -> {24};
+  24 -> {30};
+  25 -> {26};
+  26 -> {27};
+  27 -> {28};
+  28 -> {29};
+  29 -> {30};
+  30 -> {31};
+  31 -> {32};
+  32 -> {33};
+  33 -> {34};
+  34 -> {35};
+  35 -> {36 39};
+  36 -> {37};
+  37 -> {38};
+  38 -> {70};
+  39 -> {40};
+  40 -> {41};
+  41 -> {42};
+  42 -> {43 48};
+  43 -> {44};
+  44 -> {45};
+  45 -> {46};
+  46 -> {47};
+  47 -> {70};
+  48 -> {49};
+  49 -> {50};
+  50 -> {51};
+  51 -> {52 61};
+  52 -> {53};
+  53 -> {54};
+  54 -> {55};
+  55 -> {56};
+  56 -> {57};
+  57 -> {58};
+  58 -> {59};
+  59 -> {60};
+  60 -> {70};
+  61 -> {62};
+  62 -> {63};
+  63 -> {64};
+  64 -> {65};
+  65 -> {66};
+  66 -> {67};
+  67 -> {68};
+  68 -> {69};
+  69 -> {70};
+  70 -> {71};
+  71 -> {72};
+}
+
+subgraph test_2 {
+  73 [shape=box label="Enter function test_2"];
+  74 [shape=box label="Enter block"];
+  75 [shape=box label="Enter when"];
+  76 [shape=box label="Access variable R|<local>/x|"];
+  77 [shape=box label="Enter when branch condition "];
+  78 [shape=box label="Type operator: A"];
+  79 [shape=box label="Exit when branch condition"];
+  80 [shape=box label="Enter block"];
+  81 [shape=box label="Access variable R|<local>/x|"];
+  82 [shape=box label="Function call: R|<local>/x|.R|/A.foo|()"];
+  83 [shape=box label="Exit block"];
+  84 [shape=box label="Exit when branch result"];
+  85 [shape=box label="Enter when branch condition "];
+  86 [shape=box label="Type operator: B"];
+  87 [shape=box label="Exit when branch condition"];
+  88 [shape=box label="Enter block"];
+  89 [shape=box label="Access variable R|<local>/x|"];
+  90 [shape=box label="Function call: R|<local>/x|.R|/B.bar|()"];
+  91 [shape=box label="Exit block"];
+  92 [shape=box label="Exit when branch result"];
+  93 [shape=box label="Enter when branch condition else"];
+  94 [shape=box label="Exit when branch condition"];
+  95 [shape=box label="Enter block"];
+  96 [shape=box label="Exit block"];
+  97 [shape=box label="Exit when branch result"];
+  98 [shape=box label="Exit when"];
+  99 [shape=box label="Enter when"];
+  100 [shape=box label="Access variable R|<local>/x|"];
+  101 [shape=box label="Enter when branch condition "];
+  102 [shape=box label="Type operator: A"];
+  103 [shape=box label="Exit when branch condition"];
+  104 [shape=box label="Enter block"];
+  105 [shape=box label="Exit block"];
+  106 [shape=box label="Exit when branch result"];
+  107 [shape=box label="Enter when branch condition "];
+  108 [shape=box label="Type operator: B"];
+  109 [shape=box label="Exit when branch condition"];
+  110 [shape=box label="Enter block"];
+  111 [shape=box label="Access variable R|<local>/x|"];
+  112 [shape=box label="Function call: R|<local>/x|.R|/A.foo|()"];
+  113 [shape=box label="Exit block"];
+  114 [shape=box label="Exit when branch result"];
+  115 [shape=box label="Enter when branch condition "];
+  116 [shape=box label="Type operator: Int"];
+  117 [shape=box label="Exit when branch condition"];
+  118 [shape=box label="Enter block"];
+  119 [shape=box label="Access variable R|<local>/x|"];
+  120 [shape=box label="Function call: R|<local>/x|.R|/A.foo|()"];
+  121 [shape=box label="Access variable R|<local>/x|"];
+  122 [shape=box label="Function call: R|<local>/x|.R|/B.bar|()"];
+  123 [shape=box label="Access variable R|<local>/x|"];
+  124 [shape=box label="Function call: R|<local>/x|.R|kotlin/Int.inc|()"];
+  125 [shape=box label="Exit block"];
+  126 [shape=box label="Exit when branch result"];
+  127 [shape=box label="Enter when branch condition else"];
+  128 [shape=box label="Exit when branch condition"];
+  129 [shape=box label="Enter block"];
+  130 [shape=box label="Access variable R|<local>/x|"];
+  131 [shape=box label="Function call: R|<local>/x|.R|/A.foo|()"];
+  132 [shape=box label="Access variable R|<local>/x|"];
+  133 [shape=box label="Function call: R|<local>/x|.R|/B.bar|()"];
+  134 [shape=box label="Exit block"];
+  135 [shape=box label="Exit when branch result"];
+  136 [shape=box label="Exit when"];
+  137 [shape=box label="Exit block"];
+  138 [shape=box label="Exit function test_2"];
+
+  73 -> {74};
+  74 -> {75};
+  75 -> {76};
+  76 -> {77};
+  77 -> {78};
+  78 -> {79};
+  79 -> {80 85};
+  80 -> {81};
+  81 -> {82};
+  82 -> {83};
+  83 -> {84};
+  84 -> {98};
+  85 -> {86};
+  86 -> {87};
+  87 -> {88 93};
+  88 -> {89};
+  89 -> {90};
+  90 -> {91};
+  91 -> {92};
+  92 -> {98};
+  93 -> {94};
+  94 -> {95};
+  95 -> {96};
+  96 -> {97};
+  97 -> {98};
+  98 -> {99};
+  99 -> {100};
+  100 -> {101};
+  101 -> {102};
+  102 -> {103};
+  103 -> {104 107};
+  104 -> {105};
+  105 -> {106};
+  106 -> {136};
+  107 -> {108};
+  108 -> {109};
+  109 -> {110 115};
+  110 -> {111};
+  111 -> {112};
+  112 -> {113};
+  113 -> {114};
+  114 -> {136};
+  115 -> {116};
+  116 -> {117};
+  117 -> {118 127};
+  118 -> {119};
+  119 -> {120};
+  120 -> {121};
+  121 -> {122};
+  122 -> {123};
+  123 -> {124};
+  124 -> {125};
+  125 -> {126};
+  126 -> {136};
+  127 -> {128};
+  128 -> {129};
+  129 -> {130};
+  130 -> {131};
+  131 -> {132};
+  132 -> {133};
+  133 -> {134};
+  134 -> {135};
+  135 -> {136};
+  136 -> {137};
+  137 -> {138};
+}
+
+subgraph test_3 {
+  139 [shape=box label="Enter function test_3"];
+  140 [shape=box label="Enter block"];
+  141 [shape=box label="Enter when"];
+  142 [shape=box label="Access variable R|<local>/x|"];
+  143 [shape=box label="Variable declaration: lval y: R|kotlin/Any?|"];
+  144 [shape=box label="Enter when branch condition "];
+  145 [shape=box label="Type operator: A"];
+  146 [shape=box label="Exit when branch condition"];
+  147 [shape=box label="Enter block"];
+  148 [shape=box label="Access variable R|<local>/x|"];
+  149 [shape=box label="Function call: R|<local>/x|.<Unresolved name: foo>#()"];
+  150 [shape=box label="Access variable R|<local>/y|"];
+  151 [shape=box label="Function call: R|<local>/y|.R|/A.foo|()"];
+  152 [shape=box label="Exit block"];
+  153 [shape=box label="Exit when branch result"];
+  154 [shape=box label="Enter when branch condition "];
+  155 [shape=box label="Type operator: B"];
+  156 [shape=box label="Exit when branch condition"];
+  157 [shape=box label="Enter block"];
+  158 [shape=box label="Access variable R|<local>/x|"];
+  159 [shape=box label="Function call: R|<local>/x|.<Unresolved name: bar>#()"];
+  160 [shape=box label="Access variable R|<local>/y|"];
+  161 [shape=box label="Function call: R|<local>/y|.R|/B.bar|()"];
+  162 [shape=box label="Exit block"];
+  163 [shape=box label="Exit when branch result"];
+  164 [shape=box label="Enter when branch condition else"];
+  165 [shape=box label="Exit when branch condition"];
+  166 [shape=box label="Enter block"];
+  167 [shape=box label="Exit block"];
+  168 [shape=box label="Exit when branch result"];
+  169 [shape=box label="Exit when"];
+  170 [shape=box label="Enter when"];
+  171 [shape=box label="Access variable R|<local>/x|"];
+  172 [shape=box label="Variable declaration: lval y: R|kotlin/Any?|"];
+  173 [shape=box label="Enter when branch condition "];
+  174 [shape=box label="Type operator: A"];
+  175 [shape=box label="Exit when branch condition"];
+  176 [shape=box label="Enter block"];
+  177 [shape=box label="Exit block"];
+  178 [shape=box label="Exit when branch result"];
+  179 [shape=box label="Enter when branch condition "];
+  180 [shape=box label="Type operator: B"];
+  181 [shape=box label="Exit when branch condition"];
+  182 [shape=box label="Enter block"];
+  183 [shape=box label="Access variable R|<local>/x|"];
+  184 [shape=box label="Function call: R|<local>/x|.<Unresolved name: foo>#()"];
+  185 [shape=box label="Access variable R|<local>/y|"];
+  186 [shape=box label="Function call: R|<local>/y|.R|/A.foo|()"];
+  187 [shape=box label="Exit block"];
+  188 [shape=box label="Exit when branch result"];
+  189 [shape=box label="Enter when branch condition "];
+  190 [shape=box label="Type operator: Int"];
+  191 [shape=box label="Exit when branch condition"];
+  192 [shape=box label="Enter block"];
+  193 [shape=box label="Access variable R|<local>/x|"];
+  194 [shape=box label="Function call: R|<local>/x|.<Unresolved name: foo>#()"];
+  195 [shape=box label="Access variable R|<local>/x|"];
+  196 [shape=box label="Function call: R|<local>/x|.<Unresolved name: bar>#()"];
+  197 [shape=box label="Access variable R|<local>/x|"];
+  198 [shape=box label="Function call: R|<local>/x|.<Ambiguity: inc, [kotlin/inc, kotlin/inc]>#()"];
+  199 [shape=box label="Access variable R|<local>/y|"];
+  200 [shape=box label="Function call: R|<local>/y|.R|/A.foo|()"];
+  201 [shape=box label="Access variable R|<local>/y|"];
+  202 [shape=box label="Function call: R|<local>/y|.R|/B.bar|()"];
+  203 [shape=box label="Access variable R|<local>/y|"];
+  204 [shape=box label="Function call: R|<local>/y|.R|kotlin/Int.inc|()"];
+  205 [shape=box label="Exit block"];
+  206 [shape=box label="Exit when branch result"];
+  207 [shape=box label="Enter when branch condition else"];
+  208 [shape=box label="Exit when branch condition"];
+  209 [shape=box label="Enter block"];
+  210 [shape=box label="Access variable R|<local>/x|"];
+  211 [shape=box label="Function call: R|<local>/x|.<Unresolved name: foo>#()"];
+  212 [shape=box label="Access variable R|<local>/x|"];
+  213 [shape=box label="Function call: R|<local>/x|.<Unresolved name: bar>#()"];
+  214 [shape=box label="Access variable R|<local>/y|"];
+  215 [shape=box label="Function call: R|<local>/y|.R|/A.foo|()"];
+  216 [shape=box label="Access variable R|<local>/y|"];
+  217 [shape=box label="Function call: R|<local>/y|.R|/B.bar|()"];
+  218 [shape=box label="Exit block"];
+  219 [shape=box label="Exit when branch result"];
+  220 [shape=box label="Exit when"];
+  221 [shape=box label="Exit block"];
+  222 [shape=box label="Exit function test_3"];
+
+  139 -> {140};
+  140 -> {141};
+  141 -> {142};
+  142 -> {143};
+  143 -> {144};
+  144 -> {145};
+  145 -> {146};
+  146 -> {147 154};
+  147 -> {148};
+  148 -> {149};
+  149 -> {150};
+  150 -> {151};
+  151 -> {152};
+  152 -> {153};
+  153 -> {169};
+  154 -> {155};
+  155 -> {156};
+  156 -> {157 164};
+  157 -> {158};
+  158 -> {159};
+  159 -> {160};
+  160 -> {161};
+  161 -> {162};
+  162 -> {163};
+  163 -> {169};
+  164 -> {165};
+  165 -> {166};
+  166 -> {167};
+  167 -> {168};
+  168 -> {169};
+  169 -> {170};
+  170 -> {171};
+  171 -> {172};
+  172 -> {173};
+  173 -> {174};
+  174 -> {175};
+  175 -> {176 179};
+  176 -> {177};
+  177 -> {178};
+  178 -> {220};
+  179 -> {180};
+  180 -> {181};
+  181 -> {182 189};
+  182 -> {183};
+  183 -> {184};
+  184 -> {185};
+  185 -> {186};
+  186 -> {187};
+  187 -> {188};
+  188 -> {220};
+  189 -> {190};
+  190 -> {191};
+  191 -> {192 207};
+  192 -> {193};
+  193 -> {194};
+  194 -> {195};
+  195 -> {196};
+  196 -> {197};
+  197 -> {198};
+  198 -> {199};
+  199 -> {200};
+  200 -> {201};
+  201 -> {202};
+  202 -> {203};
+  203 -> {204};
+  204 -> {205};
+  205 -> {206};
+  206 -> {220};
+  207 -> {208};
+  208 -> {209};
+  209 -> {210};
+  210 -> {211};
+  211 -> {212};
+  212 -> {213};
+  213 -> {214};
+  214 -> {215};
+  215 -> {216};
+  216 -> {217};
+  217 -> {218};
+  218 -> {219};
+  219 -> {220};
+  220 -> {221};
+  221 -> {222};
+}
+
+subgraph test_4 {
+  223 [shape=box label="Enter function test_4"];
+  224 [shape=box label="Enter block"];
+  225 [shape=box label="Enter when"];
+  226 [shape=box label="Access variable R|<local>/x|"];
+  227 [shape=box label="Type operator: x as Int"];
+  228 [shape=box label="Enter when branch condition "];
+  229 [shape=box label="Const: Int(1)"];
+  230 [shape=box label="Operator =="];
+  231 [shape=box label="Exit when branch condition"];
+  232 [shape=box label="Enter block"];
+  233 [shape=box label="Access variable R|<local>/x|"];
+  234 [shape=box label="Function call: R|<local>/x|.R|kotlin/Int.inc|()"];
+  235 [shape=box label="Exit block"];
+  236 [shape=box label="Exit when branch result"];
+  237 [shape=box label="Enter when branch condition else"];
+  238 [shape=box label="Exit when branch condition"];
+  239 [shape=box label="Enter block"];
+  240 [shape=box label="Exit block"];
+  241 [shape=box label="Exit when branch result"];
+  242 [shape=box label="Exit when"];
+  243 [shape=box label="Access variable R|<local>/x|"];
+  244 [shape=box label="Function call: R|<local>/x|.R|kotlin/Int.inc|()"];
+  245 [shape=box label="Exit block"];
+  246 [shape=box label="Exit function test_4"];
+
+  223 -> {224};
+  224 -> {225};
+  225 -> {226};
+  226 -> {227};
+  227 -> {228};
+  228 -> {229};
+  229 -> {230};
+  230 -> {231};
+  231 -> {232 237};
+  232 -> {233};
+  233 -> {234};
+  234 -> {235};
+  235 -> {236};
+  236 -> {242};
+  237 -> {238};
+  238 -> {239};
+  239 -> {240};
+  240 -> {241};
+  241 -> {242};
+  242 -> {243};
+  243 -> {244};
+  244 -> {245};
+  245 -> {246};
+}
+
+}
diff --git a/compiler/fir/resolve/testData/resolve/smartcasts/when.kt b/compiler/fir/resolve/testData/resolve/smartcasts/when.kt
new file mode 100644
index 00000000000..587bb5c90df
--- /dev/null
+++ b/compiler/fir/resolve/testData/resolve/smartcasts/when.kt
@@ -0,0 +1,91 @@
+interface A {
+    fun foo()
+}
+
+interface B {
+    fun bar()
+}
+
+fun test_1(x: Any?) {
+    when {
+        x is A -> x.foo()
+        x is B -> x.bar()
+    }
+
+    when {
+        x !is A -> {}
+        x !is B -> x.foo()
+        x is Int -> {
+            x.foo()
+            x.bar()
+            x.inc()
+        }
+        else -> {
+            x.foo()
+            x.bar()
+        }
+    }
+}
+
+fun test_2(x: Any?) {
+    when(x) {
+        is A -> x.foo()
+        is B -> x.bar()
+    }
+
+    when(x) {
+        !is A -> {}
+        !is B -> x.foo()
+        is Int -> {
+            x.foo()
+            x.bar()
+            x.inc()
+        }
+        else -> {
+            x.foo()
+            x.bar()
+        }
+    }
+}
+
+fun test_3(x: Any?) {
+    when(val y = x) {
+        is A -> {
+            x.foo()
+            y.foo()
+        }
+        is B -> {
+            x.bar()
+            y.bar()
+        }
+    }
+
+    when(val y = x) {
+        !is A -> {}
+        !is B -> {
+            x.foo()
+            y.foo()
+        }
+        is Int -> {
+            x.foo()
+            x.bar()
+            x.inc()
+            y.foo()
+            y.bar()
+            y.inc()
+        }
+        else -> {
+            x.foo()
+            x.bar()
+            y.foo()
+            y.bar()
+        }
+    }
+}
+
+fun test_4(x: Any) {
+    when (x as Int) {
+        1 -> x.inc()
+    }
+    x.inc()
+}
\ No newline at end of file
diff --git a/compiler/fir/resolve/testData/resolve/smartcasts/when.txt b/compiler/fir/resolve/testData/resolve/smartcasts/when.txt
new file mode 100644
index 00000000000..398d56f733d
--- /dev/null
+++ b/compiler/fir/resolve/testData/resolve/smartcasts/when.txt
@@ -0,0 +1,118 @@
+FILE: when.kt
+    public abstract interface A : R|kotlin/Any| {
+        public abstract fun foo(): R|kotlin/Unit|
+
+    }
+    public abstract interface B : R|kotlin/Any| {
+        public abstract fun bar(): R|kotlin/Unit|
+
+    }
+    public final fun test_1(x: R|kotlin/Any?|): R|kotlin/Unit| {
+        when () {
+            (R|<local>/x| is R|A|) ->  {
+                R|<local>/x|.R|/A.foo|()
+            }
+            (R|<local>/x| is R|B|) ->  {
+                R|<local>/x|.R|/B.bar|()
+            }
+            else ->  {
+            }
+        }
+
+        when () {
+            (R|<local>/x| !is R|A|) ->  {
+            }
+            (R|<local>/x| !is R|B|) ->  {
+                R|<local>/x|.R|/A.foo|()
+            }
+            (R|<local>/x| is R|kotlin/Int|) ->  {
+                R|<local>/x|.R|/A.foo|()
+                R|<local>/x|.R|/B.bar|()
+                R|<local>/x|.R|kotlin/Int.inc|()
+            }
+            else ->  {
+                R|<local>/x|.R|/A.foo|()
+                R|<local>/x|.R|/B.bar|()
+            }
+        }
+
+    }
+    public final fun test_2(x: R|kotlin/Any?|): R|kotlin/Unit| {
+        when (R|<local>/x|) {
+            ($subj$ is R|A|) ->  {
+                R|<local>/x|.R|/A.foo|()
+            }
+            ($subj$ is R|B|) ->  {
+                R|<local>/x|.R|/B.bar|()
+            }
+            else ->  {
+            }
+        }
+
+        when (R|<local>/x|) {
+            ($subj$ !is R|A|) ->  {
+            }
+            ($subj$ !is R|B|) ->  {
+                R|<local>/x|.R|/A.foo|()
+            }
+            ($subj$ is R|kotlin/Int|) ->  {
+                R|<local>/x|.R|/A.foo|()
+                R|<local>/x|.R|/B.bar|()
+                R|<local>/x|.R|kotlin/Int.inc|()
+            }
+            else ->  {
+                R|<local>/x|.R|/A.foo|()
+                R|<local>/x|.R|/B.bar|()
+            }
+        }
+
+    }
+    public final fun test_3(x: R|kotlin/Any?|): R|kotlin/Unit| {
+        when (lval y: R|kotlin/Any?| = R|<local>/x|) {
+            ($subj$ is R|A|) ->  {
+                R|<local>/x|.<Unresolved name: foo>#()
+                R|<local>/y|.R|/A.foo|()
+            }
+            ($subj$ is R|B|) ->  {
+                R|<local>/x|.<Unresolved name: bar>#()
+                R|<local>/y|.R|/B.bar|()
+            }
+            else ->  {
+            }
+        }
+
+        when (lval y: R|kotlin/Any?| = R|<local>/x|) {
+            ($subj$ !is R|A|) ->  {
+            }
+            ($subj$ !is R|B|) ->  {
+                R|<local>/x|.<Unresolved name: foo>#()
+                R|<local>/y|.R|/A.foo|()
+            }
+            ($subj$ is R|kotlin/Int|) ->  {
+                R|<local>/x|.<Unresolved name: foo>#()
+                R|<local>/x|.<Unresolved name: bar>#()
+                R|<local>/x|.<Ambiguity: inc, [kotlin/inc, kotlin/inc]>#()
+                R|<local>/y|.R|/A.foo|()
+                R|<local>/y|.R|/B.bar|()
+                R|<local>/y|.R|kotlin/Int.inc|()
+            }
+            else ->  {
+                R|<local>/x|.<Unresolved name: foo>#()
+                R|<local>/x|.<Unresolved name: bar>#()
+                R|<local>/y|.R|/A.foo|()
+                R|<local>/y|.R|/B.bar|()
+            }
+        }
+
+    }
+    public final fun test_4(x: R|kotlin/Any|): R|kotlin/Unit| {
+        when ((R|<local>/x| as R|kotlin/Int|)) {
+            ==($subj$, Int(1)) ->  {
+                R|<local>/x|.R|kotlin/Int.inc|()
+            }
+            else ->  {
+            }
+        }
+
+        R|<local>/x|.R|kotlin/Int.inc|()
+    }
diff --git a/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirCfgBuildingTestGenerated.java b/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirCfgBuildingTestGenerated.java
index a933584c1e5..aea185ee899 100644
--- a/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirCfgBuildingTestGenerated.java
+++ b/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirCfgBuildingTestGenerated.java
@@ -118,5 +118,10 @@ public class FirCfgBuildingTestGenerated extends AbstractFirCfgBuildingTest {
         public void testSimpleIf() throws Exception {
             runTest("compiler/fir/resolve/testData/resolve/smartcasts/simpleIf.kt");
         }
+
+        @TestMetadata("when.kt")
+        public void testWhen() throws Exception {
+            runTest("compiler/fir/resolve/testData/resolve/smartcasts/when.kt");
+        }
     }
 }