[FIR] Resolve elvis call as special synthetic call

Before that commit we desugared `a ?: b` as

when (val elvis = a) {
    null -> b
    else -> elvis
}

It was incorrect, because `a` should be resolved in dependent mode,
  but when it was `elvis` initializer it was resolved in independent
  mode, so we can't infer type for `a` in some complex cases

compiler/fir/analysis-tests/testData/resolve/delegates/delegateWithLambda.txt

@@ -24,15 +24,7 @@ FILE: delegateWithLambda.kt
         }
 
         public final val x: R|kotlin/String|by R|/lazy|<R|kotlin/String|>(<L> = lazy@fun <anonymous>(): R|kotlin/String| {
-            lval y: R|kotlin/String| = when (lval <elvis>: R|kotlin/String?| = (R|/getAny|() as? R|kotlin/String|)) {
+            lval y: R|kotlin/String| = (R|/getAny|() as? R|kotlin/String|) ?: String()
-                ==($subj$, Null(null)) ->  {
-                    String()
-                }
-                else ->  {
-                    R|<local>/<elvis>|
-                }
-            }
-
             ^ R|<local>/y|
         }
         )

compiler/fir/analysis-tests/testData/resolve/expresssions/syntheticSmartCast.txt

@@ -16,27 +16,11 @@ FILE: test.kt
 
     }
     public final fun test1(x: R|AnotherClass?|): R|kotlin/Unit| {
-        lval bar: R|kotlin/CharSequence| = when (lval <elvis>: R|kotlin/CharSequence?| = R|<local>/x|?.{ $subj$.R|/AnotherClass.bar| }) {
+        lval bar: R|kotlin/CharSequence| = R|<local>/x|?.{ $subj$.R|/AnotherClass.bar| } ?: ^test1 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test1 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/x|.R|/AnotherClass.bar|
     }
     public final fun test2(x: R|SomeClass?|): R|kotlin/Unit| {
-        lval bar: R|kotlin/CharSequence| = when (lval <elvis>: R|kotlin/CharSequence?| = R|<local>/x|?.{ $subj$.R|/SomeClass.bar| }) {
+        lval bar: R|kotlin/CharSequence| = R|<local>/x|?.{ $subj$.R|/SomeClass.bar| } ?: ^test2 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test2 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/x|.R|/SomeClass.bar|
     }
     public final fun test3(x: R|AnotherClass?|): R|kotlin/Unit| {
@@ -58,62 +42,22 @@ FILE: test.kt
 
     }
     public final fun test5(x: R|AnotherClass?|): R|kotlin/Unit| {
-        lval bar: R|kotlin/String| = when (lval <elvis>: R|kotlin/String?| = (R|<local>/x|?.{ $subj$.R|/AnotherClass.bar| } as? R|kotlin/String|)) {
+        lval bar: R|kotlin/String| = (R|<local>/x|?.{ $subj$.R|/AnotherClass.bar| } as? R|kotlin/String|) ?: ^test5 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test5 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/x|.R|/AnotherClass.foo|
     }
     public final fun test6(x: R|SomeClass?|): R|kotlin/Unit| {
-        lval bar: R|kotlin/String| = when (lval <elvis>: R|kotlin/String?| = (R|<local>/x|?.{ $subj$.R|/SomeClass.bar| } as? R|kotlin/String|)) {
+        lval bar: R|kotlin/String| = (R|<local>/x|?.{ $subj$.R|/SomeClass.bar| } as? R|kotlin/String|) ?: ^test6 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test6 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/x|.R|/SomeClass.foo|
     }
     public final fun test7(x: R|AnotherClass?|): R|kotlin/Unit| {
-        lval baz: R|kotlin/Boolean| = when (lval <elvis>: R|kotlin/Boolean?| = (R|<local>/x|?.{ $subj$.R|/AnotherClass.baz|() } as? R|kotlin/Boolean|)) {
+        lval baz: R|kotlin/Boolean| = (R|<local>/x|?.{ $subj$.R|/AnotherClass.baz|() } as? R|kotlin/Boolean|) ?: ^test7 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test7 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/x|.R|/AnotherClass.foo|
     }
     public final fun test8(x: R|AnotherClass?|): R|kotlin/Unit| {
-        lval bar: R|kotlin/CharSequence| = when (lval <elvis>: R|kotlin/CharSequence?| = R|<local>/x|?.{ $subj$.R|/AnotherClass.bar| }) {
+        lval bar: R|kotlin/CharSequence| = R|<local>/x|?.{ $subj$.R|/AnotherClass.bar| } ?: ^test8 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test8 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/x|.R|/AnotherClass.foo|
     }
     public final fun test9(x: R|AnotherClass?|): R|kotlin/Unit| {
-        lval baz: R|kotlin/Any| = when (lval <elvis>: R|kotlin/Any?| = R|<local>/x|?.{ $subj$.R|/AnotherClass.baz|() }) {
+        lval baz: R|kotlin/Any| = R|<local>/x|?.{ $subj$.R|/AnotherClass.baz|() } ?: ^test9 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test9 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/x|.R|/AnotherClass.foo|
     }

compiler/fir/analysis-tests/testData/resolve/inference/lambdaInElvis.kt

@@ -0,0 +1,18 @@
+// ISSUE: KT-39012
+
+interface A
+
+fun <T> foo(f: (MutableList<T>) -> Unit): List<T>? = TODO()
+fun <T> listOf(): List<T> = TODO()
+
+fun bar1(w: List<CharSequence>): List<CharSequence>? {
+    return foo { container ->
+        container.add("")
+    } ?: w
+}
+
+fun bar2(): List<CharSequence>? {
+    return foo { container ->
+        container.add("")
+    } ?: listOf()
+}

compiler/fir/analysis-tests/testData/resolve/inference/lambdaInElvis.txt

@@ -0,0 +1,21 @@
+FILE: lambdaInElvis.kt
+    public abstract interface A : R|kotlin/Any| {
+    }
+    public final fun <T> foo(f: R|(kotlin/collections/MutableList<T>) -> kotlin/Unit|): R|kotlin/collections/List<T>?| {
+        ^foo R|kotlin/TODO|()
+    }
+    public final fun <T> listOf(): R|kotlin/collections/List<T>| {
+        ^listOf R|kotlin/TODO|()
+    }
+    public final fun bar1(w: R|kotlin/collections/List<kotlin/CharSequence>|): R|kotlin/collections/List<kotlin/CharSequence>?| {
+        ^bar1 R|/foo|<R|kotlin/CharSequence|>(<L> = foo@fun <anonymous>(container: R|kotlin/collections/MutableList<kotlin/CharSequence>|): R|kotlin/Unit| {
+            ^ R|<local>/container|.R|FakeOverride<kotlin/collections/MutableList.add: R|kotlin/Boolean|>|(String())
+        }
+        ) ?: R|<local>/w|
+    }
+    public final fun bar2(): R|kotlin/collections/List<kotlin/CharSequence>?| {
+        ^bar2 R|/foo|<R|kotlin/CharSequence|>(<L> = foo@fun <anonymous>(container: R|kotlin/collections/MutableList<kotlin/CharSequence>|): R|kotlin/Unit| {
+            ^ R|<local>/container|.R|FakeOverride<kotlin/collections/MutableList.add: R|kotlin/Boolean|>|(String())
+        }
+        ) ?: R|/listOf|<R|kotlin/CharSequence|>()
+    }

compiler/fir/analysis-tests/testData/resolve/invokeInWhenSubjectVariableInitializer.txt

@@ -1,12 +1,4 @@
 FILE: invokeInWhenSubjectVariableInitializer.kt
     public final fun test(func: R|() -> kotlin/String?|): R|kotlin/Unit| {
-        lval x: R|kotlin/String| = when (lval <elvis>: R|kotlin/String?| = R|<local>/func|.R|FakeOverride<kotlin/Function0.invoke: R|kotlin/String?|>|()) {
+        lval x: R|kotlin/String| = R|<local>/func|.R|FakeOverride<kotlin/Function0.invoke: R|kotlin/String?|>|() ?: String()
-            ==($subj$, Null(null)) ->  {
-                String()
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
     }

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

@@ -366,81 +366,75 @@ digraph boundSmartcasts_kt {
         subgraph cluster_34 {
             color=blue
             130 [label="Enter block"];
-            subgraph cluster_35 {
+            131 [label="Access variable R|<local>/d|"];
-                color=blue
+            132 [label="Access variable R|/D.any|"];
-                131 [label="Enter when"];
+            133 [label="Exit lhs of ?:"];
-                132 [label="Access variable R|<local>/d|"];
+            134 [label="Enter rhs of ?:"];
-                133 [label="Access variable R|/D.any|"];
+            135 [label="Jump: ^test_5 Unit"];
-                134 [label="Variable declaration: lval <elvis>: R|kotlin/Any?|"];
+            136 [label="Stub" style="filled" fillcolor=gray];
-                subgraph cluster_36 {
+            137 [label="Lhs of ?: is not null"];
-                    color=blue
+            138 [label="Exit ?:"];
-                    135 [label="Enter when branch condition "];
+            139 [label="Variable declaration: lval a: R|kotlin/Any|"];
-                    136 [label="Const: Null(null)"];
+            140 [label="Access variable R|<local>/a|"];
-                    137 [label="Operator =="];
+            141 [label="Function call: R|<local>/a|.R|/baz|()"];
-                    138 [label="Exit when branch condition"];
+            142 [label="Access variable R|<local>/d|"];
-                }
+            143 [label="Access variable R|/D.any|"];
-                subgraph cluster_37 {
+            144 [label="Function call: R|<local>/d|.R|/D.any|.R|/baz|()"];
-                    color=blue
+            145 [label="Access variable R|<local>/a|"];
-                    139 [label="Enter when branch condition else"];
+            146 [label="Type operator: (R|<local>/a| as R|A|)"];
-                    140 [label="Exit when branch condition"];
+            147 [label="Access variable R|<local>/a|"];
-                }
+            148 [label="Function call: R|<local>/a|.R|/A.foo|()"];
-                141 [label="Enter when branch result"];
+            149 [label="Exit block"];
-                subgraph cluster_38 {
-                    color=blue
-                    142 [label="Enter block"];
-                    143 [label="Access variable R|<local>/<elvis>|"];
-                    144 [label="Exit block"];
-                }
-                145 [label="Exit when branch result"];
-                146 [label="Enter when branch result"];
-                subgraph cluster_39 {
-                    color=blue
-                    147 [label="Enter block"];
-                    148 [label="Jump: ^test_5 Unit"];
-                    149 [label="Stub" style="filled" fillcolor=gray];
-                    150 [label="Exit block" style="filled" fillcolor=gray];
-                }
-                151 [label="Exit when branch result" style="filled" fillcolor=gray];
-                152 [label="Exit when"];
-            }
-            153 [label="Variable declaration: lval a: R|kotlin/Any|"];
-            154 [label="Access variable R|<local>/a|"];
-            155 [label="Function call: R|<local>/a|.R|/baz|()"];
-            156 [label="Access variable R|<local>/d|"];
-            157 [label="Access variable R|/D.any|"];
-            158 [label="Function call: R|<local>/d|.R|/D.any|.R|/baz|()"];
-            159 [label="Access variable R|<local>/a|"];
-            160 [label="Type operator: (R|<local>/a| as R|A|)"];
-            161 [label="Access variable R|<local>/a|"];
-            162 [label="Function call: R|<local>/a|.R|/A.foo|()"];
-            163 [label="Exit block"];
         }
-        164 [label="Exit function test_5" style="filled" fillcolor=red];
+        150 [label="Exit function test_5" style="filled" fillcolor=red];
     }
     129 -> {130};
     130 -> {131};
     131 -> {132};
     132 -> {133};
-    133 -> {134};
+    133 -> {137 134};
     134 -> {135};
-    135 -> {136};
+    135 -> {150};
-    136 -> {137};
+    135 -> {136} [style=dotted];
+    136 -> {138} [style=dotted];
     137 -> {138};
-    138 -> {146 139};
+    138 -> {139};
     139 -> {140};
     140 -> {141};
     141 -> {142};
     142 -> {143};
     143 -> {144};
     144 -> {145};
-    145 -> {152};
+    145 -> {146};
     146 -> {147};
     147 -> {148};
-    148 -> {164};
+    148 -> {149};
-    148 -> {149} [style=dotted];
+    149 -> {150};
-    149 -> {150} [style=dotted];
+
-    150 -> {151} [style=dotted];
+    subgraph cluster_35 {
-    151 -> {152} [style=dotted];
+        color=red
+        151 [label="Enter function test_6" style="filled" fillcolor=red];
+        subgraph cluster_36 {
+            color=blue
+            152 [label="Enter block"];
+            153 [label="Access variable R|<local>/d1|"];
+            154 [label="Access variable R|/D.any|"];
+            155 [label="Variable declaration: lval a: R|kotlin/Any?|"];
+            156 [label="Access variable R|<local>/a|"];
+            157 [label="Type operator: (R|<local>/a| as R|A|)"];
+            158 [label="Access variable R|<local>/a|"];
+            159 [label="Function call: R|<local>/a|.R|/A.foo|()"];
+            160 [label="Access variable R|<local>/d1|"];
+            161 [label="Access variable R|/D.any|"];
+            162 [label="Function call: R|<local>/d1|.R|/D.any|.R|/A.foo|()"];
+            163 [label="Access variable R|<local>/d1|"];
+            164 [label="Access variable R|/D.any|"];
+            165 [label="Function call: R|<local>/d1|.R|/D.any|.R|/baz|()"];
+            166 [label="Exit block"];
+        }
+        167 [label="Exit function test_6" style="filled" fillcolor=red];
+    }
+    151 -> {152};
     152 -> {153};
     153 -> {154};
     154 -> {155};
@@ -453,95 +447,58 @@ digraph boundSmartcasts_kt {
     161 -> {162};
     162 -> {163};
     163 -> {164};
-
+    164 -> {165};
-    subgraph cluster_40 {
-        color=red
-        165 [label="Enter function test_6" style="filled" fillcolor=red];
-        subgraph cluster_41 {
-            color=blue
-            166 [label="Enter block"];
-            167 [label="Access variable R|<local>/d1|"];
-            168 [label="Access variable R|/D.any|"];
-            169 [label="Variable declaration: lval a: R|kotlin/Any?|"];
-            170 [label="Access variable R|<local>/a|"];
-            171 [label="Type operator: (R|<local>/a| as R|A|)"];
-            172 [label="Access variable R|<local>/a|"];
-            173 [label="Function call: R|<local>/a|.R|/A.foo|()"];
-            174 [label="Access variable R|<local>/d1|"];
-            175 [label="Access variable R|/D.any|"];
-            176 [label="Function call: R|<local>/d1|.R|/D.any|.R|/A.foo|()"];
-            177 [label="Access variable R|<local>/d1|"];
-            178 [label="Access variable R|/D.any|"];
-            179 [label="Function call: R|<local>/d1|.R|/D.any|.R|/baz|()"];
-            180 [label="Exit block"];
-        }
-        181 [label="Exit function test_6" style="filled" fillcolor=red];
-    }
     165 -> {166};
     166 -> {167};
-    167 -> {168};
+
+    subgraph cluster_37 {
+        color=red
+        168 [label="Enter function test_7" style="filled" fillcolor=red];
+        subgraph cluster_38 {
+            color=blue
+            169 [label="Enter block"];
+            170 [label="Access variable R|<local>/d1|"];
+            171 [label="Enter safe call"];
+            172 [label="Access variable R|/D.any|"];
+            173 [label="Exit safe call"];
+            174 [label="Variable declaration: lval a: R|kotlin/Any?|"];
+            175 [label="Access variable R|<local>/d2|"];
+            176 [label="Enter safe call"];
+            177 [label="Access variable R|/D.any|"];
+            178 [label="Exit safe call"];
+            179 [label="Variable declaration: lval b: R|kotlin/Any?|"];
+            180 [label="Access variable R|<local>/a|"];
+            181 [label="Type operator: (R|<local>/a| as R|A|)"];
+            182 [label="Access variable R|<local>/a|"];
+            183 [label="Function call: R|<local>/a|.R|/A.foo|()"];
+            184 [label="Access variable R|<local>/b|"];
+            185 [label="Type operator: (R|<local>/b| as R|B|)"];
+            186 [label="Access variable R|<local>/b|"];
+            187 [label="Function call: R|<local>/b|.R|/B.bar|()"];
+            188 [label="Exit block"];
+        }
+        189 [label="Exit function test_7" style="filled" fillcolor=red];
+    }
     168 -> {169};
     169 -> {170};
-    170 -> {171};
+    170 -> {171 173};
     171 -> {172};
     172 -> {173};
     173 -> {174};
     174 -> {175};
-    175 -> {176};
+    175 -> {176 178};
     176 -> {177};
     177 -> {178};
     178 -> {179};
     179 -> {180};
     180 -> {181};
-
+    181 -> {182};
-    subgraph cluster_42 {
-        color=red
-        182 [label="Enter function test_7" style="filled" fillcolor=red];
-        subgraph cluster_43 {
-            color=blue
-            183 [label="Enter block"];
-            184 [label="Access variable R|<local>/d1|"];
-            185 [label="Enter safe call"];
-            186 [label="Access variable R|/D.any|"];
-            187 [label="Exit safe call"];
-            188 [label="Variable declaration: lval a: R|kotlin/Any?|"];
-            189 [label="Access variable R|<local>/d2|"];
-            190 [label="Enter safe call"];
-            191 [label="Access variable R|/D.any|"];
-            192 [label="Exit safe call"];
-            193 [label="Variable declaration: lval b: R|kotlin/Any?|"];
-            194 [label="Access variable R|<local>/a|"];
-            195 [label="Type operator: (R|<local>/a| as R|A|)"];
-            196 [label="Access variable R|<local>/a|"];
-            197 [label="Function call: R|<local>/a|.R|/A.foo|()"];
-            198 [label="Access variable R|<local>/b|"];
-            199 [label="Type operator: (R|<local>/b| as R|B|)"];
-            200 [label="Access variable R|<local>/b|"];
-            201 [label="Function call: R|<local>/b|.R|/B.bar|()"];
-            202 [label="Exit block"];
-        }
-        203 [label="Exit function test_7" style="filled" fillcolor=red];
-    }
     182 -> {183};
     183 -> {184};
-    184 -> {185 187};
+    184 -> {185};
     185 -> {186};
     186 -> {187};
     187 -> {188};
     188 -> {189};
-    189 -> {190 192};
-    190 -> {191};
-    191 -> {192};
-    192 -> {193};
-    193 -> {194};
-    194 -> {195};
-    195 -> {196};
-    196 -> {197};
-    197 -> {198};
-    198 -> {199};
-    199 -> {200};
-    200 -> {201};
-    201 -> {202};
-    202 -> {203};
 
 }

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

@@ -70,15 +70,7 @@ FILE: boundSmartcasts.kt
     public final fun R|kotlin/Any|.baz(): R|kotlin/Unit| {
     }
     public final fun test_5(d: R|D|): R|kotlin/Unit| {
-        lval a: R|kotlin/Any| = when (lval <elvis>: R|kotlin/Any?| = R|<local>/d|.R|/D.any|) {
+        lval a: R|kotlin/Any| = R|<local>/d|.R|/D.any| ?: ^test_5 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test_5 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/a|.R|/baz|()
         R|<local>/d|.R|/D.any|.R|/baz|()
         (R|<local>/a| as R|A|)

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

@@ -36,122 +36,102 @@ digraph elvis_kt {
                 subgraph cluster_6 {
                     color=blue
                     9 [label="Enter when branch condition "];
-                    subgraph cluster_7 {
+                    10 [label="Access variable R|<local>/x|"];
-                        color=blue
+                    11 [label="Enter safe call"];
-                        10 [label="Enter when"];
+                    12 [label="Access variable R|/A.b|"];
-                        11 [label="Access variable R|<local>/x|"];
+                    13 [label="Exit safe call"];
-                        12 [label="Enter safe call"];
+                    14 [label="Exit lhs of ?:"];
-                        13 [label="Access variable R|/A.b|"];
+                    15 [label="Enter rhs of ?:"];
-                        14 [label="Exit safe call"];
+                    16 [label="Jump: ^test_1 Unit"];
-                        15 [label="Variable declaration: lval <elvis>: R|kotlin/Boolean?|"];
+                    17 [label="Stub" style="filled" fillcolor=gray];
-                        subgraph cluster_8 {
+                    18 [label="Lhs of ?: is not null"];
-                            color=blue
+                    19 [label="Exit ?:"];
-                            16 [label="Enter when branch condition "];
+                    20 [label="Exit when branch condition"];
-                            17 [label="Const: Null(null)"];
-                            18 [label="Operator =="];
-                            19 [label="Exit when branch condition"];
-                        }
-                        subgraph cluster_9 {
-                            color=blue
-                            20 [label="Enter when branch condition else"];
-                            21 [label="Exit when branch condition"];
-                        }
-                        22 [label="Enter when branch result"];
-                        subgraph cluster_10 {
-                            color=blue
-                            23 [label="Enter block"];
-                            24 [label="Access variable R|<local>/<elvis>|"];
-                            25 [label="Exit block"];
-                        }
-                        26 [label="Exit when branch result"];
-                        27 [label="Enter when branch result"];
-                        subgraph cluster_11 {
-                            color=blue
-                            28 [label="Enter block"];
-                            29 [label="Jump: ^test_1 Unit"];
-                            30 [label="Stub" style="filled" fillcolor=gray];
-                            31 [label="Exit block" style="filled" fillcolor=gray];
-                        }
-                        32 [label="Exit when branch result" style="filled" fillcolor=gray];
-                        33 [label="Exit when"];
-                    }
-                    34 [label="Exit when branch condition"];
                 }
-                35 [label="Synthetic else branch"];
+                21 [label="Synthetic else branch"];
-                36 [label="Enter when branch result"];
+                22 [label="Enter when branch result"];
-                subgraph cluster_12 {
+                subgraph cluster_7 {
                     color=blue
-                    37 [label="Enter block"];
+                    23 [label="Enter block"];
-                    38 [label="Access variable R|<local>/x|"];
+                    24 [label="Access variable R|<local>/x|"];
-                    39 [label="Function call: R|<local>/x|.R|/A.foo|()"];
+                    25 [label="Function call: R|<local>/x|.R|/A.foo|()"];
-                    40 [label="Exit block"];
+                    26 [label="Exit block"];
                 }
-                41 [label="Exit when branch result"];
+                27 [label="Exit when branch result"];
-                42 [label="Exit when"];
+                28 [label="Exit when"];
             }
-            43 [label="Exit block"];
+            29 [label="Exit block"];
         }
-        44 [label="Exit function test_1" style="filled" fillcolor=red];
+        30 [label="Exit function test_1" style="filled" fillcolor=red];
     }
     6 -> {7};
     7 -> {8};
     8 -> {9};
     9 -> {10};
-    10 -> {11};
+    10 -> {11 13};
-    11 -> {12 14};
+    11 -> {12};
     12 -> {13};
     13 -> {14};
-    14 -> {15};
+    14 -> {18 15};
     15 -> {16};
-    16 -> {17};
+    16 -> {30};
-    17 -> {18};
+    16 -> {17} [style=dotted];
+    17 -> {19} [style=dotted];
     18 -> {19};
-    19 -> {27 20};
+    19 -> {20};
-    20 -> {21};
+    20 -> {22 21};
-    21 -> {22};
+    21 -> {28};
     22 -> {23};
     23 -> {24};
     24 -> {25};
     25 -> {26};
-    26 -> {33};
+    26 -> {27};
     27 -> {28};
     28 -> {29};
-    29 -> {44};
+    29 -> {30};
-    29 -> {30} [style=dotted];
-    30 -> {31} [style=dotted];
-    31 -> {32} [style=dotted];
-    32 -> {33} [style=dotted];
-    33 -> {34};
-    34 -> {36 35};
-    35 -> {42};
-    36 -> {37};
-    37 -> {38};
-    38 -> {39};
-    39 -> {40};
-    40 -> {41};
-    41 -> {42};
-    42 -> {43};
-    43 -> {44};
 
-    subgraph cluster_13 {
+    subgraph cluster_8 {
         color=red
-        45 [label="Enter function test2" style="filled" fillcolor=red];
+        31 [label="Enter function test2" style="filled" fillcolor=red];
-        subgraph cluster_14 {
+        subgraph cluster_9 {
             color=blue
-            46 [label="Enter block"];
+            32 [label="Enter block"];
-            subgraph cluster_15 {
+            subgraph cluster_10 {
+                color=blue
+                33 [label="Enter when"];
+                subgraph cluster_11 {
+                    color=blue
+                    34 [label="Enter when branch condition "];
+                    35 [label="Access variable R|<local>/b|"];
+                    36 [label="Type operator: (R|<local>/b| !is R|kotlin/String|)"];
+                    37 [label="Exit when branch condition"];
+                }
+                38 [label="Synthetic else branch"];
+                39 [label="Enter when branch result"];
+                subgraph cluster_12 {
+                    color=blue
+                    40 [label="Enter block"];
+                    41 [label="Const: String()"];
+                    42 [label="Jump: ^test2 String()"];
+                    43 [label="Stub" style="filled" fillcolor=gray];
+                    44 [label="Exit block" style="filled" fillcolor=gray];
+                }
+                45 [label="Exit when branch result" style="filled" fillcolor=gray];
+                46 [label="Exit when"];
+            }
+            subgraph cluster_13 {
                 color=blue
                 47 [label="Enter when"];
-                subgraph cluster_16 {
+                subgraph cluster_14 {
                     color=blue
                     48 [label="Enter when branch condition "];
-                    49 [label="Access variable R|<local>/b|"];
+                    49 [label="Access variable R|<local>/a|"];
-                    50 [label="Type operator: (R|<local>/b| !is R|kotlin/String|)"];
+                    50 [label="Type operator: (R|<local>/a| !is R|kotlin/String?|)"];
                     51 [label="Exit when branch condition"];
                 }
                 52 [label="Synthetic else branch"];
                 53 [label="Enter when branch result"];
-                subgraph cluster_17 {
+                subgraph cluster_15 {
                     color=blue
                     54 [label="Enter block"];
                     55 [label="Const: String()"];
@@ -162,79 +142,34 @@ digraph elvis_kt {
                 59 [label="Exit when branch result" style="filled" fillcolor=gray];
                 60 [label="Exit when"];
             }
-            subgraph cluster_18 {
+            61 [label="Access variable R|<local>/a|"];
-                color=blue
+            62 [label="Exit lhs of ?:"];
-                61 [label="Enter when"];
+            63 [label="Enter rhs of ?:"];
-                subgraph cluster_19 {
+            64 [label="Access variable R|<local>/b|"];
-                    color=blue
+            65 [label="Lhs of ?: is not null"];
-                    62 [label="Enter when branch condition "];
+            66 [label="Exit ?:"];
-                    63 [label="Access variable R|<local>/a|"];
+            67 [label="Jump: ^test2 R|<local>/a| ?: R|<local>/b|"];
-                    64 [label="Type operator: (R|<local>/a| !is R|kotlin/String?|)"];
+            68 [label="Stub" style="filled" fillcolor=gray];
-                    65 [label="Exit when branch condition"];
+            69 [label="Exit block" style="filled" fillcolor=gray];
-                }
-                66 [label="Synthetic else branch"];
-                67 [label="Enter when branch result"];
-                subgraph cluster_20 {
-                    color=blue
-                    68 [label="Enter block"];
-                    69 [label="Const: String()"];
-                    70 [label="Jump: ^test2 String()"];
-                    71 [label="Stub" style="filled" fillcolor=gray];
-                    72 [label="Exit block" style="filled" fillcolor=gray];
-                }
-                73 [label="Exit when branch result" style="filled" fillcolor=gray];
-                74 [label="Exit when"];
-            }
-            subgraph cluster_21 {
-                color=blue
-                75 [label="Enter when"];
-                76 [label="Access variable R|<local>/a|"];
-                77 [label="Variable declaration: lval <elvis>: R|kotlin/String?|"];
-                subgraph cluster_22 {
-                    color=blue
-                    78 [label="Enter when branch condition "];
-                    79 [label="Const: Null(null)"];
-                    80 [label="Operator =="];
-                    81 [label="Exit when branch condition"];
-                }
-                subgraph cluster_23 {
-                    color=blue
-                    82 [label="Enter when branch condition else"];
-                    83 [label="Exit when branch condition"];
-                }
-                84 [label="Enter when branch result"];
-                subgraph cluster_24 {
-                    color=blue
-                    85 [label="Enter block"];
-                    86 [label="Access variable R|<local>/<elvis>|"];
-                    87 [label="Exit block"];
-                }
-                88 [label="Exit when branch result"];
-                89 [label="Enter when branch result"];
-                subgraph cluster_25 {
-                    color=blue
-                    90 [label="Enter block"];
-                    91 [label="Access variable R|<local>/b|"];
-                    92 [label="Exit block"];
-                }
-                93 [label="Exit when branch result"];
-                94 [label="Exit when"];
-            }
-            95 [label="Jump: ^test2 when (lval <elvis>: R|kotlin/String?| = R|<local>/a|) {
-    ==($subj$, Null(null)) ->  {
-        R|<local>/b|
-    }
-    else ->  {
-        R|<local>/<elvis>|
-    }
-}
-"];
-            96 [label="Stub" style="filled" fillcolor=gray];
-            97 [label="Exit block" style="filled" fillcolor=gray];
         }
-        98 [label="Exit function test2" style="filled" fillcolor=red];
+        70 [label="Exit function test2" style="filled" fillcolor=red];
     }
-    45 -> {46};
+    31 -> {32};
+    32 -> {33};
+    33 -> {34};
+    34 -> {35};
+    35 -> {36};
+    36 -> {37};
+    37 -> {39 38};
+    38 -> {46};
+    39 -> {40};
+    40 -> {41};
+    41 -> {42};
+    42 -> {70};
+    42 -> {43} [style=dotted];
+    43 -> {44} [style=dotted];
+    44 -> {45} [style=dotted];
+    45 -> {46} [style=dotted];
     46 -> {47};
     47 -> {48};
     48 -> {49};
@@ -245,50 +180,21 @@ digraph elvis_kt {
     53 -> {54};
     54 -> {55};
     55 -> {56};
-    56 -> {98};
+    56 -> {70};
     56 -> {57} [style=dotted];
     57 -> {58} [style=dotted];
     58 -> {59} [style=dotted];
     59 -> {60} [style=dotted];
     60 -> {61};
     61 -> {62};
-    62 -> {63};
+    62 -> {65 63};
     63 -> {64};
-    64 -> {65};
+    64 -> {66};
-    65 -> {67 66};
+    65 -> {66};
-    66 -> {74};
+    66 -> {67};
-    67 -> {68};
+    67 -> {70};
-    68 -> {69};
+    67 -> {68} [style=dotted];
-    69 -> {70};
+    68 -> {69} [style=dotted];
-    70 -> {98};
+    69 -> {70} [style=dotted];
-    70 -> {71} [style=dotted];
-    71 -> {72} [style=dotted];
-    72 -> {73} [style=dotted];
-    73 -> {74} [style=dotted];
-    74 -> {75};
-    75 -> {76};
-    76 -> {77};
-    77 -> {78};
-    78 -> {79};
-    79 -> {80};
-    80 -> {81};
-    81 -> {89 82};
-    82 -> {83};
-    83 -> {84};
-    84 -> {85};
-    85 -> {86};
-    86 -> {87};
-    87 -> {88};
-    88 -> {94};
-    89 -> {90};
-    90 -> {91};
-    91 -> {92};
-    92 -> {93};
-    93 -> {94};
-    94 -> {95};
-    95 -> {98};
-    95 -> {96} [style=dotted];
-    96 -> {97} [style=dotted];
-    97 -> {98} [style=dotted];
 
 }

compiler/fir/analysis-tests/testData/resolve/smartcasts/controlStructures/elvis.txt

@@ -8,15 +8,7 @@ FILE: elvis.kt
     }
     public final fun test_1(x: R|A?|): R|kotlin/Unit| {
         when () {
-            when (lval <elvis>: R|kotlin/Boolean?| = R|<local>/x|?.{ $subj$.R|/A.b| }) {
+            R|<local>/x|?.{ $subj$.R|/A.b| } ?: ^test_1 Unit ->  {
-                ==($subj$, Null(null)) ->  {
-                    ^test_1 Unit
-                }
-                else ->  {
-                    R|<local>/<elvis>|
-                }
-            }
-             ->  {
                 R|<local>/x|.R|/A.foo|()
             }
         }
@@ -35,13 +27,5 @@ FILE: elvis.kt
             }
         }
 
-        ^test2 when (lval <elvis>: R|kotlin/String?| = R|<local>/a|) {
+        ^test2 R|<local>/a| ?: R|<local>/b|
-            ==($subj$, Null(null)) ->  {
-                R|<local>/b|
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
     }

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

@@ -434,104 +434,61 @@ digraph returns_kt {
             151 [label="Access variable R|<local>/a|"];
             152 [label="Type operator: (R|<local>/a| as? R|kotlin/String|)"];
             153 [label="Variable declaration: lval s: R|kotlin/String?|"];
+            154 [label="Access variable R|<local>/s|"];
+            155 [label="Enter safe call"];
+            156 [label="Access variable R|/ext|"];
+            157 [label="Exit safe call"];
+            158 [label="Exit lhs of ?:"];
+            159 [label="Enter rhs of ?:"];
+            160 [label="Jump: ^test_4 Unit"];
+            161 [label="Stub" style="filled" fillcolor=gray];
+            162 [label="Lhs of ?: is not null"];
+            163 [label="Exit ?:"];
+            164 [label="Variable declaration: lval length: R|kotlin/Int|"];
+            165 [label="Postponed enter to lambda"];
             subgraph cluster_42 {
                 color=blue
-                154 [label="Enter when"];
+                170 [label="Enter function anonymousFunction" style="filled" fillcolor=red];
-                155 [label="Access variable R|<local>/s|"];
-                156 [label="Enter safe call"];
-                157 [label="Access variable R|/ext|"];
-                158 [label="Exit safe call"];
-                159 [label="Variable declaration: lval <elvis>: R|kotlin/Int?|"];
                 subgraph cluster_43 {
                     color=blue
-                    160 [label="Enter when branch condition "];
+                    171 [label="Enter block"];
-                    161 [label="Const: Null(null)"];
+                    172 [label="Access variable R|<local>/s|"];
-                    162 [label="Operator =="];
+                    173 [label="Access variable R|kotlin/String.length|"];
-                    163 [label="Exit when branch condition"];
+                    174 [label="Exit block"];
                 }
-                subgraph cluster_44 {
+                175 [label="Exit function anonymousFunction" style="filled" fillcolor=red];
-                    color=blue
-                    164 [label="Enter when branch condition else"];
-                    165 [label="Exit when branch condition"];
-                }
-                166 [label="Enter when branch result"];
-                subgraph cluster_45 {
-                    color=blue
-                    167 [label="Enter block"];
-                    168 [label="Access variable R|<local>/<elvis>|"];
-                    169 [label="Exit block"];
-                }
-                170 [label="Exit when branch result"];
-                171 [label="Enter when branch result"];
-                subgraph cluster_46 {
-                    color=blue
-                    172 [label="Enter block"];
-                    173 [label="Jump: ^test_4 Unit"];
-                    174 [label="Stub" style="filled" fillcolor=gray];
-                    175 [label="Exit block" style="filled" fillcolor=gray];
-                }
-                176 [label="Exit when branch result" style="filled" fillcolor=gray];
-                177 [label="Exit when"];
             }
-            178 [label="Variable declaration: lval length: R|kotlin/Int|"];
+            166 [label="Postponed exit from lambda"];
-            179 [label="Postponed enter to lambda"];
+            167 [label="Function call: R|/runHigherOrder|<R|kotlin/Int|>(...)"];
-            subgraph cluster_47 {
+            168 [label="Exit block"];
-                color=blue
-                184 [label="Enter function anonymousFunction" style="filled" fillcolor=red];
-                subgraph cluster_48 {
-                    color=blue
-                    185 [label="Enter block"];
-                    186 [label="Access variable R|<local>/s|"];
-                    187 [label="Access variable R|kotlin/String.length|"];
-                    188 [label="Exit block"];
-                }
-                189 [label="Exit function anonymousFunction" style="filled" fillcolor=red];
-            }
-            180 [label="Postponed exit from lambda"];
-            181 [label="Function call: R|/runHigherOrder|<R|kotlin/Int|>(...)"];
-            182 [label="Exit block"];
         }
-        183 [label="Exit function test_4" style="filled" fillcolor=red];
+        169 [label="Exit function test_4" style="filled" fillcolor=red];
     }
     149 -> {150};
     150 -> {151};
     151 -> {152};
     152 -> {153};
     153 -> {154};
-    154 -> {155};
+    154 -> {155 157};
-    155 -> {156 158};
+    155 -> {156};
     156 -> {157};
     157 -> {158};
-    158 -> {159};
+    158 -> {162 159};
     159 -> {160};
-    160 -> {161};
+    160 -> {169};
-    161 -> {162};
+    160 -> {161} [style=dotted];
+    161 -> {163} [style=dotted];
     162 -> {163};
-    163 -> {171 164};
+    163 -> {164};
     164 -> {165};
-    165 -> {166};
+    165 -> {166 170};
     166 -> {167};
     167 -> {168};
     168 -> {169};
-    169 -> {170};
+    170 -> {171};
-    170 -> {177};
     171 -> {172};
     172 -> {173};
-    173 -> {183};
+    173 -> {174};
-    173 -> {174} [style=dotted];
+    174 -> {175};
-    174 -> {175} [style=dotted];
-    175 -> {176} [style=dotted];
-    176 -> {177} [style=dotted];
-    177 -> {178};
-    178 -> {179};
-    179 -> {180 184};
-    180 -> {181};
-    181 -> {182};
-    182 -> {183};
-    184 -> {185};
-    185 -> {186};
-    186 -> {187};
-    187 -> {188};
-    188 -> {189};
 
 }

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

@@ -74,15 +74,7 @@ FILE: returns.kt
         }
     public final fun test_4(a: R|kotlin/Any?|): R|kotlin/Unit| {
         lval s: R|kotlin/String?| = (R|<local>/a| as? R|kotlin/String|)
-        lval length: R|kotlin/Int| = when (lval <elvis>: R|kotlin/Int?| = R|<local>/s|?.{ $subj$.R|/ext| }) {
+        lval length: R|kotlin/Int| = R|<local>/s|?.{ $subj$.R|/ext| } ?: ^test_4 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test_4 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|/runHigherOrder|<R|kotlin/Int|>(<L> = runHigherOrder@fun <anonymous>(): R|kotlin/Int| {
             ^ R|<local>/s|.R|kotlin/String.length|
         }

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

@@ -50,61 +50,32 @@ digraph smartcastFromArgument_kt {
                 subgraph cluster_7 {
                     color=blue
                     14 [label="Enter when branch condition "];
-                    subgraph cluster_8 {
+                    15 [label="Access variable R|<local>/a|"];
-                        color=blue
+                    16 [label="Type operator: (R|<local>/a| as? R|A|)"];
-                        15 [label="Enter when"];
+                    17 [label="Exit lhs of ?:"];
-                        16 [label="Access variable R|<local>/a|"];
+                    18 [label="Enter rhs of ?:"];
-                        17 [label="Type operator: (R|<local>/a| as? R|A|)"];
+                    19 [label="Jump: ^test Unit"];
-                        18 [label="Variable declaration: lval <elvis>: R|A?|"];
+                    20 [label="Stub" style="filled" fillcolor=gray];
-                        subgraph cluster_9 {
+                    21 [label="Lhs of ?: is not null"];
-                            color=blue
+                    22 [label="Exit ?:"];
-                            19 [label="Enter when branch condition "];
+                    23 [label="Function call: R|/takeA|(...)"];
-                            20 [label="Const: Null(null)"];
+                    24 [label="Exit when branch condition"];
-                            21 [label="Operator =="];
-                            22 [label="Exit when branch condition"];
-                        }
-                        subgraph cluster_10 {
-                            color=blue
-                            23 [label="Enter when branch condition else"];
-                            24 [label="Exit when branch condition"];
-                        }
-                        25 [label="Enter when branch result"];
-                        subgraph cluster_11 {
-                            color=blue
-                            26 [label="Enter block"];
-                            27 [label="Access variable R|<local>/<elvis>|"];
-                            28 [label="Exit block"];
-                        }
-                        29 [label="Exit when branch result"];
-                        30 [label="Enter when branch result"];
-                        subgraph cluster_12 {
-                            color=blue
-                            31 [label="Enter block"];
-                            32 [label="Jump: ^test Unit"];
-                            33 [label="Stub" style="filled" fillcolor=gray];
-                            34 [label="Exit block" style="filled" fillcolor=gray];
-                        }
-                        35 [label="Exit when branch result" style="filled" fillcolor=gray];
-                        36 [label="Exit when"];
-                    }
-                    37 [label="Function call: R|/takeA|(...)"];
-                    38 [label="Exit when branch condition"];
                 }
-                39 [label="Synthetic else branch"];
+                25 [label="Synthetic else branch"];
-                40 [label="Enter when branch result"];
+                26 [label="Enter when branch result"];
-                subgraph cluster_13 {
+                subgraph cluster_8 {
                     color=blue
-                    41 [label="Enter block"];
+                    27 [label="Enter block"];
-                    42 [label="Access variable R|<local>/a|"];
+                    28 [label="Access variable R|<local>/a|"];
-                    43 [label="Function call: R|<local>/a|.R|/A.foo|()"];
+                    29 [label="Function call: R|<local>/a|.R|/A.foo|()"];
-                    44 [label="Exit block"];
+                    30 [label="Exit block"];
                 }
-                45 [label="Exit when branch result"];
+                31 [label="Exit when branch result"];
-                46 [label="Exit when"];
+                32 [label="Exit when"];
             }
-            47 [label="Exit block"];
+            33 [label="Exit block"];
         }
-        48 [label="Exit function test" style="filled" fillcolor=red];
+        34 [label="Exit function test" style="filled" fillcolor=red];
     }
     11 -> {12};
     12 -> {13};
@@ -112,37 +83,23 @@ digraph smartcastFromArgument_kt {
     14 -> {15};
     15 -> {16};
     16 -> {17};
-    17 -> {18};
+    17 -> {21 18};
     18 -> {19};
-    19 -> {20};
+    19 -> {34};
-    20 -> {21};
+    19 -> {20} [style=dotted];
+    20 -> {22} [style=dotted];
     21 -> {22};
-    22 -> {30 23};
+    22 -> {23};
     23 -> {24};
-    24 -> {25};
+    24 -> {26 25};
-    25 -> {26};
+    25 -> {32};
     26 -> {27};
     27 -> {28};
     28 -> {29};
-    29 -> {36};
+    29 -> {30};
     30 -> {31};
     31 -> {32};
-    32 -> {48};
+    32 -> {33};
-    32 -> {33} [style=dotted];
+    33 -> {34};
-    33 -> {34} [style=dotted];
-    34 -> {35} [style=dotted];
-    35 -> {36} [style=dotted];
-    36 -> {37};
-    37 -> {38};
-    38 -> {40 39};
-    39 -> {46};
-    40 -> {41};
-    41 -> {42};
-    42 -> {43};
-    43 -> {44};
-    44 -> {45};
-    45 -> {46};
-    46 -> {47};
-    47 -> {48};
 
 }

compiler/fir/analysis-tests/testData/resolve/smartcasts/controlStructures/smartcastFromArgument.txt

@@ -8,15 +8,7 @@ FILE: smartcastFromArgument.kt
     }
     public final fun test(a: R|kotlin/Any|): R|kotlin/Unit| {
         when () {
-            R|/takeA|(when (lval <elvis>: R|A?| = (R|<local>/a| as? R|A|)) {
+            R|/takeA|((R|<local>/a| as? R|A|) ?: ^test Unit) ->  {
-                ==($subj$, Null(null)) ->  {
-                    ^test Unit
-                }
-                else ->  {
-                    R|<local>/<elvis>|
-                }
-            }
-            ) ->  {
                 R|<local>/a|.R|/A.foo|()
             }
         }

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

@@ -86,15 +86,7 @@ FILE: nullability.kt
         R|<local>/x|.<Inapplicable(WRONG_RECEIVER): [/A.foo]>#()
     }
     public final fun test_3(x: R|A?|): R|kotlin/Unit| {
-        when (lval <elvis>: R|A?| = R|<local>/x|) {
+        R|<local>/x| ?: ^test_3 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test_3 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/x|.R|/A.foo|()
     }
     public final fun test_4(x: R|A?|): R|kotlin/Unit| {
@@ -117,15 +109,7 @@ FILE: nullability.kt
 
     }
     public final fun test_6(q: R|Q?|): R|kotlin/Unit| {
-        when (lval <elvis>: R|kotlin/Int?| = R|<local>/q|?.{ $subj$.R|/Q.data| }?.{ $subj$.R|/MyData.s| }?.{ $subj$.R|kotlin/Int.inc|() }) {
+        R|<local>/q|?.{ $subj$.R|/Q.data| }?.{ $subj$.R|/MyData.s| }?.{ $subj$.R|kotlin/Int.inc|() } ?: ^test_6 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test_6 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/q|.R|/Q.data|
         R|<local>/q|.R|/Q.data|.<Inapplicable(WRONG_RECEIVER): [/MyData.s]>#
         R|<local>/q|.R|/Q.data|.<Inapplicable(WRONG_RECEIVER): [/MyData.s]>#.<Unresolved name: inc>#()

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

@@ -198,164 +198,173 @@ digraph assignSafeCall_kt {
         subgraph cluster_19 {
             color=blue
             68 [label="Enter block"];
-            subgraph cluster_20 {
+            69 [label="Access variable R|<local>/x|"];
-                color=blue
+            70 [label="Type operator: (R|<local>/x| as? R|A|)"];
-                69 [label="Enter when"];
+            71 [label="Exit lhs of ?:"];
-                70 [label="Access variable R|<local>/x|"];
+            72 [label="Enter rhs of ?:"];
-                71 [label="Type operator: (R|<local>/x| as? R|A|)"];
+            73 [label="Jump: ^test_3 Unit"];
-                72 [label="Variable declaration: lval <elvis>: R|A?|"];
+            74 [label="Stub" style="filled" fillcolor=gray];
-                subgraph cluster_21 {
+            75 [label="Lhs of ?: is not null"];
-                    color=blue
+            76 [label="Exit ?:"];
-                    73 [label="Enter when branch condition "];
+            77 [label="Variable declaration: lval a: R|A|"];
-                    74 [label="Const: Null(null)"];
+            78 [label="Access variable R|<local>/a|"];
-                    75 [label="Operator =="];
+            79 [label="Function call: R|<local>/a|.R|/A.foo|()"];
-                    76 [label="Exit when branch condition"];
+            80 [label="Access variable R|<local>/x|"];
-                }
+            81 [label="Function call: R|<local>/x|.R|/A.foo|()"];
-                subgraph cluster_22 {
+            82 [label="Exit block"];
-                    color=blue
-                    77 [label="Enter when branch condition else"];
-                    78 [label="Exit when branch condition"];
-                }
-                79 [label="Enter when branch result"];
-                subgraph cluster_23 {
-                    color=blue
-                    80 [label="Enter block"];
-                    81 [label="Access variable R|<local>/<elvis>|"];
-                    82 [label="Exit block"];
-                }
-                83 [label="Exit when branch result"];
-                84 [label="Enter when branch result"];
-                subgraph cluster_24 {
-                    color=blue
-                    85 [label="Enter block"];
-                    86 [label="Jump: ^test_3 Unit"];
-                    87 [label="Stub" style="filled" fillcolor=gray];
-                    88 [label="Exit block" style="filled" fillcolor=gray];
-                }
-                89 [label="Exit when branch result" style="filled" fillcolor=gray];
-                90 [label="Exit when"];
-            }
-            91 [label="Variable declaration: lval a: R|A|"];
-            92 [label="Access variable R|<local>/a|"];
-            93 [label="Function call: R|<local>/a|.R|/A.foo|()"];
-            94 [label="Access variable R|<local>/x|"];
-            95 [label="Function call: R|<local>/x|.R|/A.foo|()"];
-            96 [label="Exit block"];
         }
-        97 [label="Exit function test_3" style="filled" fillcolor=red];
+        83 [label="Exit function test_3" style="filled" fillcolor=red];
     }
     67 -> {68};
     68 -> {69};
     69 -> {70};
     70 -> {71};
-    71 -> {72};
+    71 -> {75 72};
     72 -> {73};
-    73 -> {74};
+    73 -> {83};
-    74 -> {75};
+    73 -> {74} [style=dotted];
+    74 -> {76} [style=dotted];
     75 -> {76};
-    76 -> {84 77};
+    76 -> {77};
     77 -> {78};
     78 -> {79};
     79 -> {80};
     80 -> {81};
     81 -> {82};
     82 -> {83};
-    83 -> {90};
+
-    84 -> {85};
+    subgraph cluster_20 {
-    85 -> {86};
+        color=red
-    86 -> {97};
+        84 [label="Enter class B" style="filled" fillcolor=red];
-    86 -> {87} [style=dotted];
+        85 [label="Exit class B" style="filled" fillcolor=red];
-    87 -> {88} [style=dotted];
+    }
-    88 -> {89} [style=dotted];
+    84 -> {85} [color=green];
-    89 -> {90} [style=dotted];
+
+    subgraph cluster_21 {
+        color=red
+        86 [label="Enter function foo" style="filled" fillcolor=red];
+        87 [label="Exit function foo" style="filled" fillcolor=red];
+    }
+    86 -> {87};
+
+    subgraph cluster_22 {
+        color=red
+        88 [label="Enter function getter" style="filled" fillcolor=red];
+        89 [label="Exit function getter" style="filled" fillcolor=red];
+    }
+    88 -> {89};
+
+    subgraph cluster_23 {
+        color=red
+        90 [label="Enter function bar" style="filled" fillcolor=red];
+        91 [label="Exit function bar" style="filled" fillcolor=red];
+    }
     90 -> {91};
-    91 -> {92};
+
+    subgraph cluster_24 {
+        color=red
+        92 [label="Enter function test_1" style="filled" fillcolor=red];
+        subgraph cluster_25 {
+            color=blue
+            93 [label="Enter block"];
+            94 [label="Access variable R|<local>/a|"];
+            95 [label="Enter safe call"];
+            96 [label="Access variable R|/B.x|"];
+            97 [label="Exit safe call"];
+            98 [label="Variable declaration: lval x: R|kotlin/Int?|"];
+            subgraph cluster_26 {
+                color=blue
+                99 [label="Enter when"];
+                subgraph cluster_27 {
+                    color=blue
+                    100 [label="Enter when branch condition "];
+                    101 [label="Access variable R|<local>/x|"];
+                    102 [label="Const: Null(null)"];
+                    103 [label="Operator !="];
+                    104 [label="Exit when branch condition"];
+                }
+                105 [label="Synthetic else branch"];
+                106 [label="Enter when branch result"];
+                subgraph cluster_28 {
+                    color=blue
+                    107 [label="Enter block"];
+                    108 [label="Access variable R|<local>/a|"];
+                    109 [label="Function call: R|<local>/a|.R|/B.bar|()"];
+                    110 [label="Exit block"];
+                }
+                111 [label="Exit when branch result"];
+                112 [label="Exit when"];
+            }
+            113 [label="Exit block"];
+        }
+        114 [label="Exit function test_1" style="filled" fillcolor=red];
+    }
     92 -> {93};
     93 -> {94};
-    94 -> {95};
+    94 -> {95 97};
     95 -> {96};
     96 -> {97};
-
+    97 -> {98};
-    subgraph cluster_25 {
+    98 -> {99};
-        color=red
+    99 -> {100};
-        98 [label="Enter class B" style="filled" fillcolor=red];
-        99 [label="Exit class B" style="filled" fillcolor=red];
-    }
-    98 -> {99} [color=green];
-
-    subgraph cluster_26 {
-        color=red
-        100 [label="Enter function foo" style="filled" fillcolor=red];
-        101 [label="Exit function foo" style="filled" fillcolor=red];
-    }
     100 -> {101};
-
+    101 -> {102};
-    subgraph cluster_27 {
-        color=red
-        102 [label="Enter function getter" style="filled" fillcolor=red];
-        103 [label="Exit function getter" style="filled" fillcolor=red];
-    }
     102 -> {103};
-
+    103 -> {104};
-    subgraph cluster_28 {
+    104 -> {106 105};
-        color=red
+    105 -> {112};
-        104 [label="Enter function bar" style="filled" fillcolor=red];
-        105 [label="Exit function bar" style="filled" fillcolor=red];
-    }
-    104 -> {105};
-
-    subgraph cluster_29 {
-        color=red
-        106 [label="Enter function test_1" style="filled" fillcolor=red];
-        subgraph cluster_30 {
-            color=blue
-            107 [label="Enter block"];
-            108 [label="Access variable R|<local>/a|"];
-            109 [label="Enter safe call"];
-            110 [label="Access variable R|/B.x|"];
-            111 [label="Exit safe call"];
-            112 [label="Variable declaration: lval x: R|kotlin/Int?|"];
-            subgraph cluster_31 {
-                color=blue
-                113 [label="Enter when"];
-                subgraph cluster_32 {
-                    color=blue
-                    114 [label="Enter when branch condition "];
-                    115 [label="Access variable R|<local>/x|"];
-                    116 [label="Const: Null(null)"];
-                    117 [label="Operator !="];
-                    118 [label="Exit when branch condition"];
-                }
-                119 [label="Synthetic else branch"];
-                120 [label="Enter when branch result"];
-                subgraph cluster_33 {
-                    color=blue
-                    121 [label="Enter block"];
-                    122 [label="Access variable R|<local>/a|"];
-                    123 [label="Function call: R|<local>/a|.R|/B.bar|()"];
-                    124 [label="Exit block"];
-                }
-                125 [label="Exit when branch result"];
-                126 [label="Exit when"];
-            }
-            127 [label="Exit block"];
-        }
-        128 [label="Exit function test_1" style="filled" fillcolor=red];
-    }
     106 -> {107};
     107 -> {108};
-    108 -> {109 111};
+    108 -> {109};
     109 -> {110};
     110 -> {111};
     111 -> {112};
     112 -> {113};
     113 -> {114};
-    114 -> {115};
+
+    subgraph cluster_29 {
+        color=red
+        115 [label="Enter function test_2" style="filled" fillcolor=red];
+        subgraph cluster_30 {
+            color=blue
+            116 [label="Enter block"];
+            117 [label="Access variable R|<local>/a|"];
+            118 [label="Enter safe call"];
+            119 [label="Function call: $subj$.R|/B.foo|()"];
+            120 [label="Exit safe call"];
+            121 [label="Variable declaration: lval x: R|kotlin/Int?|"];
+            subgraph cluster_31 {
+                color=blue
+                122 [label="Enter when"];
+                subgraph cluster_32 {
+                    color=blue
+                    123 [label="Enter when branch condition "];
+                    124 [label="Access variable R|<local>/x|"];
+                    125 [label="Const: Null(null)"];
+                    126 [label="Operator !="];
+                    127 [label="Exit when branch condition"];
+                }
+                128 [label="Synthetic else branch"];
+                129 [label="Enter when branch result"];
+                subgraph cluster_33 {
+                    color=blue
+                    130 [label="Enter block"];
+                    131 [label="Access variable R|<local>/a|"];
+                    132 [label="Function call: R|<local>/a|.R|/B.bar|()"];
+                    133 [label="Exit block"];
+                }
+                134 [label="Exit when branch result"];
+                135 [label="Exit when"];
+            }
+            136 [label="Exit block"];
+        }
+        137 [label="Exit function test_2" style="filled" fillcolor=red];
+    }
     115 -> {116};
     116 -> {117};
-    117 -> {118};
+    117 -> {118 120};
-    118 -> {120 119};
+    118 -> {119};
-    119 -> {126};
+    119 -> {120};
     120 -> {121};
     121 -> {122};
     122 -> {123};
@@ -363,151 +372,56 @@ digraph assignSafeCall_kt {
     124 -> {125};
     125 -> {126};
     126 -> {127};
-    127 -> {128};
+    127 -> {129 128};
-
+    128 -> {135};
-    subgraph cluster_34 {
-        color=red
-        129 [label="Enter function test_2" style="filled" fillcolor=red];
-        subgraph cluster_35 {
-            color=blue
-            130 [label="Enter block"];
-            131 [label="Access variable R|<local>/a|"];
-            132 [label="Enter safe call"];
-            133 [label="Function call: $subj$.R|/B.foo|()"];
-            134 [label="Exit safe call"];
-            135 [label="Variable declaration: lval x: R|kotlin/Int?|"];
-            subgraph cluster_36 {
-                color=blue
-                136 [label="Enter when"];
-                subgraph cluster_37 {
-                    color=blue
-                    137 [label="Enter when branch condition "];
-                    138 [label="Access variable R|<local>/x|"];
-                    139 [label="Const: Null(null)"];
-                    140 [label="Operator !="];
-                    141 [label="Exit when branch condition"];
-                }
-                142 [label="Synthetic else branch"];
-                143 [label="Enter when branch result"];
-                subgraph cluster_38 {
-                    color=blue
-                    144 [label="Enter block"];
-                    145 [label="Access variable R|<local>/a|"];
-                    146 [label="Function call: R|<local>/a|.R|/B.bar|()"];
-                    147 [label="Exit block"];
-                }
-                148 [label="Exit when branch result"];
-                149 [label="Exit when"];
-            }
-            150 [label="Exit block"];
-        }
-        151 [label="Exit function test_2" style="filled" fillcolor=red];
-    }
     129 -> {130};
     130 -> {131};
-    131 -> {132 134};
+    131 -> {132};
     132 -> {133};
     133 -> {134};
     134 -> {135};
     135 -> {136};
     136 -> {137};
-    137 -> {138};
+
+    subgraph cluster_34 {
+        color=red
+        138 [label="Enter function test_3" style="filled" fillcolor=red];
+        subgraph cluster_35 {
+            color=blue
+            139 [label="Enter block"];
+            140 [label="Access variable R|<local>/x|"];
+            141 [label="Type operator: (R|<local>/x| as? R|B|)"];
+            142 [label="Exit lhs of ?:"];
+            143 [label="Enter rhs of ?:"];
+            144 [label="Jump: ^test_3 Unit"];
+            145 [label="Stub" style="filled" fillcolor=gray];
+            146 [label="Lhs of ?: is not null"];
+            147 [label="Exit ?:"];
+            148 [label="Variable declaration: lval a: R|B|"];
+            149 [label="Access variable R|<local>/a|"];
+            150 [label="Function call: R|<local>/a|.R|/B.foo|()"];
+            151 [label="Access variable R|<local>/x|"];
+            152 [label="Function call: R|<local>/x|.R|/B.foo|()"];
+            153 [label="Exit block"];
+        }
+        154 [label="Exit function test_3" style="filled" fillcolor=red];
+    }
     138 -> {139};
     139 -> {140};
     140 -> {141};
-    141 -> {143 142};
+    141 -> {142};
-    142 -> {149};
+    142 -> {146 143};
     143 -> {144};
-    144 -> {145};
+    144 -> {154};
-    145 -> {146};
+    144 -> {145} [style=dotted];
+    145 -> {147} [style=dotted];
     146 -> {147};
     147 -> {148};
     148 -> {149};
     149 -> {150};
     150 -> {151};
-
+    151 -> {152};
-    subgraph cluster_39 {
-        color=red
-        152 [label="Enter function test_3" style="filled" fillcolor=red];
-        subgraph cluster_40 {
-            color=blue
-            153 [label="Enter block"];
-            subgraph cluster_41 {
-                color=blue
-                154 [label="Enter when"];
-                155 [label="Access variable R|<local>/x|"];
-                156 [label="Type operator: (R|<local>/x| as? R|B|)"];
-                157 [label="Variable declaration: lval <elvis>: R|B?|"];
-                subgraph cluster_42 {
-                    color=blue
-                    158 [label="Enter when branch condition "];
-                    159 [label="Const: Null(null)"];
-                    160 [label="Operator =="];
-                    161 [label="Exit when branch condition"];
-                }
-                subgraph cluster_43 {
-                    color=blue
-                    162 [label="Enter when branch condition else"];
-                    163 [label="Exit when branch condition"];
-                }
-                164 [label="Enter when branch result"];
-                subgraph cluster_44 {
-                    color=blue
-                    165 [label="Enter block"];
-                    166 [label="Access variable R|<local>/<elvis>|"];
-                    167 [label="Exit block"];
-                }
-                168 [label="Exit when branch result"];
-                169 [label="Enter when branch result"];
-                subgraph cluster_45 {
-                    color=blue
-                    170 [label="Enter block"];
-                    171 [label="Jump: ^test_3 Unit"];
-                    172 [label="Stub" style="filled" fillcolor=gray];
-                    173 [label="Exit block" style="filled" fillcolor=gray];
-                }
-                174 [label="Exit when branch result" style="filled" fillcolor=gray];
-                175 [label="Exit when"];
-            }
-            176 [label="Variable declaration: lval a: R|B|"];
-            177 [label="Access variable R|<local>/a|"];
-            178 [label="Function call: R|<local>/a|.R|/B.foo|()"];
-            179 [label="Access variable R|<local>/x|"];
-            180 [label="Function call: R|<local>/x|.R|/B.foo|()"];
-            181 [label="Exit block"];
-        }
-        182 [label="Exit function test_3" style="filled" fillcolor=red];
-    }
     152 -> {153};
     153 -> {154};
-    154 -> {155};
-    155 -> {156};
-    156 -> {157};
-    157 -> {158};
-    158 -> {159};
-    159 -> {160};
-    160 -> {161};
-    161 -> {169 162};
-    162 -> {163};
-    163 -> {164};
-    164 -> {165};
-    165 -> {166};
-    166 -> {167};
-    167 -> {168};
-    168 -> {175};
-    169 -> {170};
-    170 -> {171};
-    171 -> {182};
-    171 -> {172} [style=dotted];
-    172 -> {173} [style=dotted];
-    173 -> {174} [style=dotted];
-    174 -> {175} [style=dotted];
-    175 -> {176};
-    176 -> {177};
-    177 -> {178};
-    178 -> {179};
-    179 -> {180};
-    180 -> {181};
-    181 -> {182};
 
 }

compiler/fir/analysis-tests/testData/resolve/smartcasts/safeCalls/assignSafeCall.txt

@@ -34,15 +34,7 @@ FILE: assignSafeCall.kt
 
     }
     public final fun test_3(x: R|kotlin/Any?|): R|kotlin/Unit| {
-        lval a: R|A| = when (lval <elvis>: R|A?| = (R|<local>/x| as? R|A|)) {
+        lval a: R|A| = (R|<local>/x| as? R|A|) ?: ^test_3 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test_3 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/a|.R|/A.foo|()
         R|<local>/x|.R|/A.foo|()
     }
@@ -74,15 +66,7 @@ FILE: assignSafeCall.kt
 
     }
     public final fun test_3(x: R|kotlin/Any?|): R|kotlin/Unit| {
-        lval a: R|B| = when (lval <elvis>: R|B?| = (R|<local>/x| as? R|B|)) {
+        lval a: R|B| = (R|<local>/x| as? R|B|) ?: ^test_3 Unit
-            ==($subj$, Null(null)) ->  {
-                ^test_3 Unit
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
         R|<local>/a|.R|/B.foo|()
         R|<local>/x|.R|/B.foo|()
     }

compiler/fir/analysis-tests/testData/resolveWithStdlib/inference/ifElvisReturn.kt

@@ -0,0 +1,18 @@
+// ISSUE: KT-39074
+
+interface A
+interface B : A {
+    fun bar()
+}
+
+fun <K : A> materialize(): K? = null!!
+
+fun foo(b: B, cond: Boolean) {
+    val x = // inferred as A
+        if (cond)
+            b
+        else
+            materialize() ?: return
+
+    x.bar()
+}

compiler/fir/analysis-tests/testData/resolveWithStdlib/inference/ifElvisReturn.txt

@@ -6,25 +6,17 @@ FILE: ifElvisReturn.kt
 
     }
     public final fun <K : R|A|> materialize(): R|K?| {
-        ^materialize R|kotlin/TODO|()
+        ^materialize Null(null)!!
     }
-    public final fun foo(b: R|B|): R|kotlin/Unit| {
+    public final fun foo(b: R|B|, cond: R|kotlin/Boolean|): R|kotlin/Unit| {
-        lval x: R|A| = when () {
+        lval x: R|B| = when () {
-            CMP(>, R|<local>/b|.R|kotlin/Any.hashCode|().R|kotlin/Int.compareTo|(Int(0))) ->  {
+            R|<local>/cond| ->  {
                 R|<local>/b|
             }
             else ->  {
-                when (lval <elvis>: R|A?| = R|/materialize|<R|A|>()) {
+                R|/materialize|<R|kotlin/Nothing|>() ?: ^foo Unit
-                    ==($subj$, Null(null)) ->  {
-                        ^foo Unit
-                    }
-                    else ->  {
-                        R|<local>/<elvis>|
-                    }
-                }
-
             }
         }
 
-        R|<local>/x|.<Unresolved name: bar>#()
+        R|<local>/x|.R|/B.bar|()
     }

compiler/fir/analysis-tests/testData/resolveWithStdlib/j+k/MapCompute.txt

@@ -1,15 +1,7 @@
 FILE: MapCompute.kt
     public final fun <D> R|kotlin/collections/MutableMap<kotlin/String, kotlin/collections/MutableSet<D>>|.initAndAdd(key: R|kotlin/String|, value: R|D|): R|kotlin/Unit| {
         this@R|/initAndAdd|.R|FakeOverride<kotlin/collections/MutableMap.compute: R|kotlin/collections/MutableSet<D>?|>|(R|<local>/key|, <L> = compute@fun <anonymous>(_: R|ft<kotlin/String, kotlin/String?>!|, maybeValues: R|ft<kotlin/collections/MutableSet<D>, kotlin/collections/MutableSet<D>?>!|): R|ft<kotlin/collections/MutableSet<D>, kotlin/collections/MutableSet<D>?>!| {
-            lval setOfValues: R|kotlin/collections/MutableSet<D>| = when (lval <elvis>: R|ft<kotlin/collections/MutableSet<D>, kotlin/collections/MutableSet<D>?>!| = R|<local>/maybeValues|) {
+            lval setOfValues: R|kotlin/collections/MutableSet<D>| = R|<local>/maybeValues| ?: R|kotlin/collections/mutableSetOf|<R|D|>()
-                ==($subj$, Null(null)) ->  {
-                    R|kotlin/collections/mutableSetOf|<R|D|>()
-                }
-                else ->  {
-                    R|<local>/<elvis>|
-                }
-            }
-
             R|<local>/setOfValues|.R|FakeOverride<kotlin/collections/MutableSet.add: R|kotlin/Boolean|>|(R|<local>/value|)
             ^ R|<local>/setOfValues|
         }

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirDiagnosticsTestGenerated.java

@@ -1484,6 +1484,11 @@ public class FirDiagnosticsTestGenerated extends AbstractFirDiagnosticsTest {
             runTest("compiler/fir/analysis-tests/testData/resolve/inference/lambdaAsReturnStatementOfLambda.kt");
         }
 
+        @TestMetadata("lambdaInElvis.kt")
+        public void testLambdaInElvis() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/resolve/inference/lambdaInElvis.kt");
+        }
+
         @TestMetadata("nestedExtensionFunctionType.kt")
         public void testNestedExtensionFunctionType() throws Exception {
             runTest("compiler/fir/analysis-tests/testData/resolve/inference/nestedExtensionFunctionType.kt");

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirDiagnosticsWithLightTreeTestGenerated.java

@@ -1484,6 +1484,11 @@ public class FirDiagnosticsWithLightTreeTestGenerated extends AbstractFirDiagnos
             runTest("compiler/fir/analysis-tests/testData/resolve/inference/lambdaAsReturnStatementOfLambda.kt");
         }
 
+        @TestMetadata("lambdaInElvis.kt")
+        public void testLambdaInElvis() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/resolve/inference/lambdaInElvis.kt");
+        }
+
         @TestMetadata("nestedExtensionFunctionType.kt")
         public void testNestedExtensionFunctionType() throws Exception {
             runTest("compiler/fir/analysis-tests/testData/resolve/inference/nestedExtensionFunctionType.kt");

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirDiagnosticsWithStdlibTestGenerated.java

@@ -711,6 +711,11 @@ public class FirDiagnosticsWithStdlibTestGenerated extends AbstractFirDiagnostic
         public void testFlexibleTypeInSystem() throws Exception {
             runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/inference/flexibleTypeInSystem.kt");
         }
+
+        @TestMetadata("ifElvisReturn.kt")
+        public void testIfElvisReturn() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/inference/ifElvisReturn.kt");
+        }
     }
 
     @TestMetadata("compiler/fir/analysis-tests/testData/resolveWithStdlib/j+k")

compiler/fir/cones/src/org/jetbrains/kotlin/fir/symbols/SyntheticCallableId.kt

@@ -9,20 +9,28 @@ import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 
 object SyntheticCallableId {
+    private val syntheticPackageName: FqName = FqName("_synthetic")
+
     val WHEN = CallableId(
-        FqName("_synthetic"),
+        syntheticPackageName,
         Name.identifier("WHEN_CALL")
     )
     val TRY = CallableId(
-        FqName("_synthetic"),
+        syntheticPackageName,
         Name.identifier("TRY_CALL")
     )
     val CHECK_NOT_NULL = CallableId(
-        FqName("_synthetic"),
+        syntheticPackageName,
         Name.identifier("CHECK_NOT_NULL_CALL")
     )
+
+    val ELVIS_NOT_NULL = CallableId(
+        syntheticPackageName,
+        Name.identifier("ELVIS_CALL")
+    )
+
     val ID = CallableId(
-        FqName("_synthetic"),
+        syntheticPackageName,
         Name.identifier("ID_CALL")
     )
 }

compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt

@@ -1359,6 +1359,12 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
         +"!!"
     }
 
+    private fun FlowContent.generate(elvisCall: FirElvisCall) {
+        generate(elvisCall.lhs)
+        +" ?: "
+        generate(elvisCall.rhs)
+    }
+
     @Suppress("UNUSED_PARAMETER")
     private fun FlowContent.generate(elseIfTrueCondition: FirElseIfTrueCondition) {
         keyword("else")
@@ -1563,6 +1569,7 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
                 is FirOperatorCall -> generate(expression)
                 is FirBinaryLogicExpression -> generate(expression)
                 is FirCheckNotNullCall -> generate(expression)
+                is FirElvisCall -> generate(expression)
                 is FirVarargArgumentsExpression -> generate(expression)
                 is FirResolvedReifiedParameterReference -> generate(expression)
                 is FirComparisonExpression -> generate(expression)

compiler/fir/raw-fir/fir-common/src/org/jetbrains/kotlin/fir/builder/ConversionUtils.kt

@@ -141,45 +141,12 @@ fun IElementType.toFirOperation(): FirOperation =
     }
 
 fun FirExpression.generateNotNullOrOther(
-    session: FirSession, other: FirExpression, caseId: String, baseSource: FirSourceElement?,
+    other: FirExpression, baseSource: FirSourceElement?,
-): FirWhenExpression {
+): FirElvisCall {
-    val subjectName = Name.special("<$caseId>")
+    return buildElvisCall {
-    val subjectSource = baseSource?.withKind(FirFakeSourceElementKind.WhenGeneratedSubject)
-    val subjectVariable = generateTemporaryVariable(session, subjectSource, subjectName, this)
-
-    @OptIn(FirContractViolation::class)
-    val ref = FirExpressionRef<FirWhenExpression>()
-    val subjectExpression = buildWhenSubjectExpression {
-        source = subjectSource
-        whenRef = ref
-    }
-
-    return buildWhenExpression {
         source = baseSource
-        this.subject = this@generateNotNullOrOther
+        lhs = this@generateNotNullOrOther
-        this.subjectVariable = subjectVariable
+        rhs = other
-        branches += buildWhenBranch {
-            val branchSource = baseSource?.withKind(FirFakeSourceElementKind.WhenCondition)
-            source = branchSource
-            condition = buildOperatorCall {
-                source = branchSource
-                operation = FirOperation.EQ
-                argumentList = buildBinaryArgumentList(
-                    subjectExpression, buildConstExpression(branchSource, FirConstKind.Null, null)
-                )
-            }
-            result = buildSingleExpressionBlock(other)
-        }
-        branches += buildWhenBranch {
-            val otherSource = other.source?.withKind(FirFakeSourceElementKind.WhenCondition)
-            source = otherSource
-            condition = buildElseIfTrueCondition {
-                source = otherSource
-            }
-            result = buildSingleExpressionBlock(generateResolvedAccessExpression(otherSource, subjectVariable))
-        }
-    }.also {
-        ref.bind(it)
     }
 }
 

compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/converter/ExpressionsConverter.kt

@@ -246,7 +246,7 @@ class ExpressionsConverter(
 
         when (operationToken) {
             ELVIS ->
-                return leftArgAsFir.generateNotNullOrOther(baseSession, rightArgAsFir, "elvis", baseSource)
+                return leftArgAsFir.generateNotNullOrOther(rightArgAsFir, baseSource)
             ANDAND, OROR ->
                 return leftArgAsFir.generateLazyLogicalOperation(rightArgAsFir, operationToken == ANDAND, baseSource)
             in OperatorConventions.IN_OPERATIONS ->

compiler/fir/raw-fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/RawFirBuilder.kt

@@ -1554,7 +1554,7 @@ class RawFirBuilder(
 
             when (operationToken) {
                 ELVIS ->
-                    return leftArgument.generateNotNullOrOther(baseSession, rightArgument, "elvis", source)
+                    return leftArgument.generateNotNullOrOther(rightArgument, source)
                 ANDAND, OROR ->
                     return leftArgument.generateLazyLogicalOperation(rightArgument, operationToken == ANDAND, source)
                 in OperatorConventions.IN_OPERATIONS ->

compiler/fir/raw-fir/psi2fir/testData/rawBuilder/expressions/nullability.txt

@@ -1,14 +1,6 @@
 FILE: nullability.kt
     public? final? fun orFourtyTwo(arg: Int?): <implicit> {
-        ^orFourtyTwo when (lval <elvis>: <implicit> = arg#) {
+        ^orFourtyTwo arg# ?: IntegerLiteral(42)
-            ==($subj$, Null(null)) ->  {
-                IntegerLiteral(42)
-            }
-            else ->  {
-                R|<local>/<elvis>|
-            }
-        }
-
     }
     public? final? fun bang(arg: Int?): <implicit> {
         ^bang arg#!!

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Arguments.kt

@@ -42,7 +42,7 @@ fun Candidate.resolveArgumentExpression(
     isDispatch: Boolean
 ) {
     when (argument) {
-        is FirFunctionCall, is FirWhenExpression, is FirTryExpression, is FirCheckNotNullCall -> resolveSubCallArgument(
+        is FirFunctionCall, is FirWhenExpression, is FirTryExpression, is FirCheckNotNullCall, is FirElvisCall -> resolveSubCallArgument(
             csBuilder,
             argument as FirResolvable,
             expectedType,

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/CandidateFactory.kt

@@ -116,7 +116,8 @@ fun PostponedArgumentsAnalyzer.Context.addSubsystemFromExpression(statement: Fir
         is FirWhenExpression,
         is FirTryExpression,
         is FirCheckNotNullCall,
-        is FirCallableReferenceAccess
+        is FirCallableReferenceAccess,
+        is FirElvisCall
         -> (statement as FirResolvable).candidate()?.let { addOtherSystem(it.system.asReadOnlyStorage()) }
 
         is FirSafeCallExpression -> addSubsystemFromExpression(statement.regularQualifiedAccess)

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

@@ -1015,6 +1015,37 @@ abstract class FirDataFlowAnalyzer<FLOW : Flow>(
         graphBuilder.exitContractDescription()
     }
 
+    // ----------------------------------- Elvis -----------------------------------
+
+    fun exitElvisLhs(elvisCall: FirElvisCall) {
+        val (lhsExitNode, lhsIsNotNullNode, rhsEnterNode) = graphBuilder.exitElvisLhs(elvisCall)
+        lhsExitNode.mergeIncomingFlow()
+        val flow = lhsExitNode.flow
+        val lhsVariable = variableStorage.getOrCreateVariable(flow, elvisCall.lhs)
+        rhsEnterNode.flow = logicSystem.approveStatementsInsideFlow(
+            flow,
+            lhsVariable eq null,
+            shouldForkFlow = true,
+            shouldRemoveSynthetics = false
+        )
+        lhsIsNotNullNode.flow = logicSystem.approveStatementsInsideFlow(
+            flow,
+            lhsVariable notEq null,
+            shouldForkFlow = true,
+            shouldRemoveSynthetics = false
+        ).also {
+            if (lhsVariable.isReal()) {
+                it.addTypeStatement(lhsVariable typeEq any)
+            }
+        }
+    }
+
+    fun exitElvis(callCompleted: Boolean) {
+        val (elvisExitNode, unionNode) = graphBuilder.exitElvis(callCompleted)
+        elvisExitNode.mergeIncomingFlow()
+        unionNode?.let { unionFlowFromArguments(it) }
+    }
+
     // ------------------------------------------------------ Utils ------------------------------------------------------
 
     private var CFGNode<*>.flow: FLOW

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

@@ -601,6 +601,32 @@ class ExitSafeCallNode(owner: ControlFlowGraph, override val fir: FirSafeCallExp
     }
 }
 
+// ----------------------------------- Elvis -----------------------------------
+
+class ElvisLhsExitNode(owner: ControlFlowGraph, override val fir: FirElvisCall, level: Int, id: Int) : CFGNode<FirElvisCall>(owner, level, id) {
+    override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
+        return visitor.visitElvisLhsExitNode(this, data)
+    }
+}
+
+class ElvisLhsIsNotNullNode(owner: ControlFlowGraph, override val fir: FirElvisCall, level: Int, id: Int) : CFGNode<FirElvisCall>(owner, level, id) {
+    override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
+        return visitor.visitElvisLhsIsNotNullNode(this, data)
+    }
+}
+
+class ElvisRhsEnterNode(owner: ControlFlowGraph, override val fir: FirElvisCall, level: Int, id: Int) : CFGNode<FirElvisCall>(owner, level, id) {
+    override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
+        return visitor.visitElvisRhsEnterNode(this, data)
+    }
+}
+
+class ElvisExitNode(owner: ControlFlowGraph, override val fir: FirElvisCall, level: Int, id: Int) : AbstractBinaryExitNode<FirElvisCall>(owner, level, id) {
+    override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
+        return visitor.visitElvisExitNode(this, data)
+    }
+}
+
 // ----------------------------------- Other -----------------------------------
 
 class AnnotationEnterNode(owner: ControlFlowGraph, override val fir: FirAnnotationCall, level: Int, id: Int) : CFGNode<FirAnnotationCall>(owner, level, id), EnterNodeMarker {

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

@@ -106,10 +106,15 @@ fun CFGNode<*>.render(): String =
 
                 is ContractDescriptionEnterNode -> "Enter contract description"
 
-                is AbstractBinaryExitNode -> throw IllegalStateException()
-
                 is EnterDefaultArgumentsNode -> "Enter default value of ${fir.name}"
                 is ExitDefaultArgumentsNode -> "Exit default value of ${fir.name}"
+
+                is ElvisLhsExitNode -> "Exit lhs of ?:"
+                is ElvisLhsIsNotNullNode -> "Lhs of ?: is not null"
+                is ElvisRhsEnterNode -> "Enter rhs of ?:"
+                is ElvisExitNode -> "Exit ?:"
+
+                is AbstractBinaryExitNode -> throw IllegalStateException()
             },
         )
     }

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

@@ -91,6 +91,7 @@ class ControlFlowGraphBuilder {
     private val initBlockExitNodes: Stack<InitBlockExitNode> = stackOf()
 
     private val exitSafeCallNodes: Stack<ExitSafeCallNode> = stackOf()
+    private val exitElvisCallNodes: Stack<ElvisExitNode> = stackOf()
 
     // ----------------------------------- API for node builders -----------------------------------
 
@@ -986,6 +987,37 @@ class ControlFlowGraphBuilder {
         }
     }
 
+    // ----------------------------------- Elvis -----------------------------------
+
+    fun exitElvisLhs(elvisCall: FirElvisCall): Triple<ElvisLhsExitNode, ElvisLhsIsNotNullNode, ElvisRhsEnterNode> {
+        val exitNode = createElvisExitNode(elvisCall).also {
+            exitElvisCallNodes.push(it)
+        }
+
+        val lhsExitNode = createElvisLhsExitNode(elvisCall).also {
+            popAndAddEdge(it)
+        }
+
+        val lhsIsNotNullNode = createElvisLhsIsNotNullNode(elvisCall).also {
+            addEdge(lhsExitNode, it)
+            addEdge(it, exitNode)
+        }
+
+        val rhsEnterNode = createElvisRhsEnterNode(elvisCall).also {
+            addEdge(lhsExitNode, it)
+        }
+        lastNodes.push(rhsEnterNode)
+        return Triple(lhsExitNode, lhsIsNotNullNode, rhsEnterNode)
+    }
+
+    fun exitElvis(callCompleted: Boolean): Pair<ElvisExitNode, UnionFunctionCallArgumentsNode?> {
+        val exitNode = exitElvisCallNodes.pop()
+        addNewSimpleNode(exitNode)
+        exitNode.updateDeadStatus()
+        val (_, unionNode) = processUnionOfArguments(exitNode, callCompleted)
+        return exitNode to unionNode
+    }
+
     // ----------------------------------- Contract description -----------------------------------
 
     fun enterContractDescription(): CFGNode<*> {

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

@@ -125,6 +125,18 @@ fun ControlFlowGraphBuilder.createAnnotationExitNode(fir: FirAnnotationCall): An
 fun ControlFlowGraphBuilder.createAnnotationEnterNode(fir: FirAnnotationCall): AnnotationEnterNode =
     AnnotationEnterNode(currentGraph, fir, levelCounter, createId())
 
+fun ControlFlowGraphBuilder.createElvisLhsIsNotNullNode(fir: FirElvisCall): ElvisLhsIsNotNullNode =
+    ElvisLhsIsNotNullNode(currentGraph, fir, levelCounter, createId())
+
+fun ControlFlowGraphBuilder.createElvisRhsEnterNode(fir: FirElvisCall): ElvisRhsEnterNode =
+    ElvisRhsEnterNode(currentGraph, fir, levelCounter, createId())
+
+fun ControlFlowGraphBuilder.createElvisLhsExitNode(fir: FirElvisCall): ElvisLhsExitNode =
+    ElvisLhsExitNode(currentGraph, fir, levelCounter, createId())
+
+fun ControlFlowGraphBuilder.createElvisExitNode(fir: FirElvisCall): ElvisExitNode =
+    ElvisExitNode(currentGraph, fir, levelCounter, createId())
+
 fun ControlFlowGraphBuilder.createVariableDeclarationNode(fir: FirProperty): VariableDeclarationNode =
     VariableDeclarationNode(currentGraph, fir, levelCounter, createId())
 

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

@@ -307,6 +307,24 @@ abstract class ControlFlowGraphVisitor<out R, in D> {
         return visitNode(node, data)
     }
 
+    // ----------------------------------- Elvis -----------------------------------
+
+    open fun visitElvisLhsExitNode(node: ElvisLhsExitNode, data: D): R {
+        return visitNode(node, data)
+    }
+
+    open fun visitElvisLhsIsNotNullNode(node: ElvisLhsIsNotNullNode, data: D): R {
+        return visitNode(node, data)
+    }
+
+    open fun visitElvisRhsEnterNode(node: ElvisRhsEnterNode, data: D): R {
+        return visitNode(node, data)
+    }
+
+    open fun visitElvisExitNode(node: ElvisExitNode, data: D): R {
+        return visitNode(node, data)
+    }
+
     // ----------------------------------- Other -----------------------------------
 
     open fun visitAnnotationEnterNode(node: AnnotationEnterNode, data: D): R {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/ConstraintSystemCompleter.kt

@@ -292,6 +292,12 @@ fun FirStatement.processAllContainingCallCandidates(processBlocks: Boolean, proc
             processCandidateIfApplicable(processor, processBlocks)
             this.arguments.forEach { it.processAllContainingCallCandidates(processBlocks, processor) }
         }
+
+        is FirElvisCall -> {
+            processCandidateIfApplicable(processor, processBlocks)
+            lhs.processAllContainingCallCandidates(processBlocks, processor)
+            rhs.processAllContainingCallCandidates(processBlocks, processor)
+        }
     }
 }
 

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirCallCompletionResultsWriterTransformer.kt

@@ -423,14 +423,21 @@ class FirCallCompletionResultsWriterTransformer(
 
     // Transformations for synthetic calls generated by FirSyntheticCallGenerator
 
-    override fun transformWhenExpression(whenExpression: FirWhenExpression, data: ExpectedArgumentType?) =
+    override fun transformWhenExpression(whenExpression: FirWhenExpression, data: ExpectedArgumentType?): CompositeTransformResult<FirStatement> {
-        transformSyntheticCall(whenExpression, data)
+        return transformSyntheticCall(whenExpression, data)
+    }
 
-    override fun transformTryExpression(tryExpression: FirTryExpression, data: ExpectedArgumentType?) =
+    override fun transformTryExpression(tryExpression: FirTryExpression, data: ExpectedArgumentType?): CompositeTransformResult<FirStatement> {
-        transformSyntheticCall(tryExpression, data)
+        return transformSyntheticCall(tryExpression, data)
+    }
 
-    override fun transformCheckNotNullCall(checkNotNullCall: FirCheckNotNullCall, data: ExpectedArgumentType?) =
+    override fun transformCheckNotNullCall(checkNotNullCall: FirCheckNotNullCall, data: ExpectedArgumentType?): CompositeTransformResult<FirStatement> {
-        transformSyntheticCall(checkNotNullCall, data)
+        return transformSyntheticCall(checkNotNullCall, data)
+    }
+
+    override fun transformElvisCall(elvisCall: FirElvisCall, data: ExpectedArgumentType?): CompositeTransformResult<FirStatement> {
+        return transformSyntheticCall(elvisCall, data)
+    }
 
     private inline fun <reified D> transformSyntheticCall(
         syntheticCall: D,

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSyntheticCallGenerator.kt

@@ -24,6 +24,7 @@ import org.jetbrains.kotlin.fir.resolve.BodyResolveComponents
 import org.jetbrains.kotlin.fir.resolve.calls.*
 import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeUnresolvedNameError
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.FirAbstractBodyResolveTransformer
+import org.jetbrains.kotlin.fir.resolvedTypeFromPrototype
 import org.jetbrains.kotlin.fir.symbols.CallableId
 import org.jetbrains.kotlin.fir.symbols.SyntheticCallableId
 import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
@@ -47,6 +48,7 @@ class FirSyntheticCallGenerator(
     private val trySelectFunction: FirSimpleFunction = generateSyntheticSelectFunction(SyntheticCallableId.TRY)
     private val idFunction: FirSimpleFunction = generateSyntheticSelectFunction(SyntheticCallableId.ID)
     private val checkNotNullFunction: FirSimpleFunction = generateSyntheticCheckNotNullFunction()
+    private val elvisFunction: FirSimpleFunction = generateSyntheticElvisFunction()
 
     fun generateCalleeForWhenExpression(whenExpression: FirWhenExpression): FirWhenExpression? {
         val stubReference = whenExpression.calleeReference
@@ -101,6 +103,22 @@ class FirSyntheticCallGenerator(
         return checkNotNullCall.transformCalleeReference(UpdateReference, reference)
     }
 
+    fun generateCalleeForElvisCall(elvisCall: FirElvisCall): FirElvisCall? {
+        if (elvisCall.calleeReference !is FirStubReference) return null
+
+        val argumentList = buildArgumentList {
+            arguments += elvisCall.lhs
+            arguments += elvisCall.rhs
+        }
+        val reference = generateCalleeReferenceWithCandidate(
+            elvisFunction,
+            argumentList,
+            SyntheticCallableId.ELVIS_NOT_NULL.callableName
+        ) ?: return null
+
+        return elvisCall.transformCalleeReference(UpdateReference, reference)
+    }
+
     fun resolveCallableReferenceWithSyntheticOuterCall(
         callableReferenceAccess: FirCallableReferenceAccess,
         expectedTypeRef: FirTypeRef?
@@ -225,6 +243,42 @@ class FirSyntheticCallGenerator(
         }.build()
     }
 
+    private fun generateSyntheticElvisFunction(): FirSimpleFunction {
+        // Synthetic function signature:
+        //   fun <K> checkNotNull(x: K?, y: K): @Exact K
+        //
+        // Note: The upper bound of `K` cannot be `Any` because of the following case:
+        //   fun <X> test(a: X, b: X) = a ?: b
+        // `X` is not a subtype of `Any` and hence cannot satisfy `K` if it had an upper bound of `Any`.
+        val functionSymbol = FirSyntheticFunctionSymbol(SyntheticCallableId.ELVIS_NOT_NULL)
+        val (typeParameter, rightArgumentType) = generateSyntheticSelectTypeParameter()
+
+        val leftArgumentType = buildResolvedTypeRef {
+            type = rightArgumentType.coneTypeUnsafe<ConeKotlinType>().withNullability(ConeNullability.NULLABLE, session.typeContext)
+        }
+
+        val returnType = rightArgumentType.resolvedTypeFromPrototype(
+            rightArgumentType.type.withAttributes(
+                ConeAttributes.create(listOf(CompilerConeAttributes.Exact))
+            )
+        )
+
+        val typeArgument = buildTypeProjectionWithVariance {
+            typeRef = returnType
+            variance = Variance.INVARIANT
+        }
+
+        return generateMemberFunction(
+            functionSymbol,
+            SyntheticCallableId.ELVIS_NOT_NULL.callableName,
+            typeArgument.typeRef
+        ).apply {
+            typeParameters += typeParameter
+            valueParameters += leftArgumentType.toValueParameter("x")
+            valueParameters += rightArgumentType.toValueParameter("y")
+        }.build()
+    }
+
     private fun generateMemberFunction(
         symbol: FirNamedFunctionSymbol, name: Name, returnType: FirTypeRef
     ): FirSimpleFunctionBuilder {

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

@@ -304,6 +304,10 @@ open class FirBodyResolveTransformer(
         return controlFlowStatementsTransformer.transformThrowExpression(throwExpression, data)
     }
 
+    override fun transformElvisCall(elvisCall: FirElvisCall, data: ResolutionMode): CompositeTransformResult<FirStatement> {
+        return controlFlowStatementsTransformer.transformElvisCall(elvisCall, data)
+    }
+
     // --------------------------------------------------------------------------
 
     fun <D> FirElement.visitNoTransform(transformer: FirTransformer<D>, data: D) {

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

@@ -208,4 +208,31 @@ class FirControlFlowStatementsResolveTransformer(transformer: FirBodyResolveTran
             dataFlowAnalyzer.exitThrowExceptionNode(it.single as FirThrowExpression)
         }
     }
+
+    // ------------------------------- Elvis -------------------------------
+
+    override fun transformElvisCall(elvisCall: FirElvisCall, data: ResolutionMode): CompositeTransformResult<FirStatement> {
+        if (elvisCall.calleeReference is FirResolvedNamedReference) return elvisCall.compose()
+        elvisCall.transformAnnotations(transformer, data)
+        elvisCall.transformLhs(transformer, ResolutionMode.ContextDependent)
+        dataFlowAnalyzer.exitElvisLhs(elvisCall)
+        elvisCall.transformRhs(transformer, ResolutionMode.ContextDependent)
+
+        var callCompleted = false
+        val result = syntheticCallGenerator.generateCalleeForElvisCall(elvisCall)?.let {
+            val completionResult = callCompleter.completeCall(elvisCall, data.expectedType)
+            callCompleted = completionResult.callCompleted
+            completionResult.result
+        } ?: run {
+            elvisCall.resultType = buildErrorTypeRef {
+                diagnostic = ConeSimpleDiagnostic("Can't resolve ?: operator call", DiagnosticKind.InferenceError)
+            }
+            callCompleted = true
+            elvisCall
+        }
+
+        dataFlowAnalyzer.exitElvis(callCompleted)
+
+        return result.compose()
+    }
 }

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/TypeUtils.kt

@@ -6,14 +6,12 @@
 package org.jetbrains.kotlin.fir.types
 
 import org.jetbrains.kotlin.fir.FirSession
-import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.symbols.ConeClassLikeLookupTag
 import org.jetbrains.kotlin.fir.symbols.ConeClassifierLookupTag
 import org.jetbrains.kotlin.fir.symbols.ConeTypeParameterLookupTag
 import org.jetbrains.kotlin.fir.symbols.impl.ConeClassLikeLookupTagImpl
-import org.jetbrains.kotlin.fir.symbols.impl.FirTypeAliasSymbol
 import org.jetbrains.kotlin.fir.types.impl.ConeClassLikeTypeImpl
 import org.jetbrains.kotlin.fir.types.impl.ConeTypeParameterTypeImpl
 import org.jetbrains.kotlin.name.ClassId
@@ -22,7 +20,6 @@ import org.jetbrains.kotlin.types.AbstractNullabilityChecker
 import org.jetbrains.kotlin.types.AbstractStrictEqualityTypeChecker
 import org.jetbrains.kotlin.types.AbstractTypeCheckerContext
 import org.jetbrains.kotlin.types.Variance
-import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 object ConeNullabilityChecker {
     fun isSubtypeOfAny(context: ConeTypeContext, type: ConeKotlinType): Boolean {
@@ -106,6 +103,21 @@ fun <T : ConeKotlinType> T.withArguments(arguments: Array<out ConeTypeProjection
     }
 }
 
+fun <T : ConeKotlinType> T.withAttributes(attributes: ConeAttributes): T {
+    if (this.attributes == attributes) {
+        return this
+    }
+
+    @Suppress("UNCHECKED_CAST")
+    return when (this) {
+        is ConeClassErrorType -> this
+        is ConeClassLikeTypeImpl -> ConeClassLikeTypeImpl(lookupTag, typeArguments, nullability.isNullable, attributes)
+        is ConeDefinitelyNotNullType -> ConeDefinitelyNotNullType.create(original.withAttributes(attributes))!!
+        is ConeTypeParameterTypeImpl -> ConeTypeParameterTypeImpl(lookupTag, nullability.isNullable, attributes)
+        else -> error("Not supported: $this: ${this.render()}")
+    } as T
+}
+
 fun ConeTypeContext.hasNullableSuperType(type: ConeKotlinType): Boolean {
     if (type is ConeClassLikeType) return false
 

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirRenderer.kt

@@ -1022,6 +1022,12 @@ class FirRenderer(builder: StringBuilder, private val mode: RenderMode = RenderM
         print("!!")
     }
 
+    override fun visitElvisCall(elvisCall: FirElvisCall) {
+        elvisCall.lhs.accept(this)
+        print(" ?: ")
+        elvisCall.rhs.accept(this)
+    }
+
     override fun visitCallableReferenceAccess(callableReferenceAccess: FirCallableReferenceAccess) {
         callableReferenceAccess.annotations.renderAnnotations()
         callableReferenceAccess.explicitReceiver?.accept(this)

compiler/testData/diagnostics/tests/inference/nothingType/discriminatedNothingAndSmartCast.fir.kt

@@ -15,5 +15,5 @@ fun test(s: String?, silent: Boolean) {
             throw Exception()
         }
 
-    s.<!INAPPLICABLE_CANDIDATE!>length<!>
+    s.length
 }

compiler/testData/diagnostics/tests/nullableTypes/uselessElvis.fir.kt

@@ -42,7 +42,7 @@ fun test() {
 inline fun <reified T : Any> reifiedNull(): T? = null
 
 fun testFrom13648() {
-    <!INAPPLICABLE_CANDIDATE!>takeNotNull<!>(reifiedNull() ?: "")
+    takeNotNull(reifiedNull() ?: "")
 }
 
 fun bar() = <!UNRESOLVED_REFERENCE!>unresolved<!>

compiler/testData/diagnostics/tests/resolve/specialConstructions/inferenceForElvis.fir.kt

@@ -3,6 +3,6 @@
 
 fun <T: Any> foo(f: (T) -> Unit): T? = null // T is used only as return type
 fun test() {
-    val x = foo { it checkType { <!INAPPLICABLE_CANDIDATE!>_<!><String>() }} ?: "" // foo() is inferred as foo<String>, which isn't very good
+    val x = foo { it checkType { _<String>() }} ?: "" // foo() is inferred as foo<String>, which isn't very good
-    val y: Any = foo { it checkType { _<Any>() } } ?: "" // but for now it's fixed by specifying expected type
+    val y: Any = foo { <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.String")!>it<!> checkType { <!INAPPLICABLE_CANDIDATE!>_<!><Any>() } } ?: "" // but for now it's fixed by specifying expected type
 }

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/32.fir.kt

@@ -6,7 +6,7 @@
 fun <T: Any, K: Any> case_1(x: T?, y: K?) {
     x as T
     y as K
-    val z = <!DEBUG_INFO_EXPRESSION_TYPE("T?!! & T?")!>x<!> ?: <!DEBUG_INFO_EXPRESSION_TYPE("K?!!")!>y<!>
+    val z = <!DEBUG_INFO_EXPRESSION_TYPE("T?!! & T?")!>x<!> ?: <!DEBUG_INFO_EXPRESSION_TYPE("K?!! & K?")!>y<!>
 
     <!DEBUG_INFO_EXPRESSION_TYPE("T?!! & T?")!>x<!>.equals(10)
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any")!>z<!>