Exhaustive when support for sealed classes #KT-7606 Fixed

When on sealed can use is (both for derived classes and objects) or just comparison (only for derived objects).
A pack of tests provided.

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhen.kt

@@ -0,0 +1,16 @@
+sealed class Sealed(val x: Int) {
+    object First: Sealed(12)
+    open class NonFirst(x: Int, val y: Int): Sealed(x) {
+        object Second: NonFirst(34, 2)
+        object Third: NonFirst(56, 3)
+    }
+}
+
+fun foo(s: Sealed): Int {
+    return when(s) {
+        is Sealed.First -> 1
+        is Sealed.NonFirst -> 0
+        // no else required
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhen.txt

@@ -0,0 +1,46 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        internal final val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenDoubleInner.kt

@@ -0,0 +1,16 @@
+sealed class Sealed() {
+    object First: Sealed()
+    open class NonFirst: Sealed() {
+        object Second: NonFirst()
+        object Third: NonFirst()
+        // It's ALLOWED to inherit Sealed also from here
+        object Fourth: Sealed()
+    }    
+}
+
+fun foo(s: Sealed) = when(s) {
+    Sealed.First -> 1
+    is Sealed.NonFirst -> 2
+    Sealed.NonFirst.Fourth -> 4
+    // no else required
+}

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenDoubleInner.txt

@@ -0,0 +1,45 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Fourth : Sealed {
+            private constructor Fourth()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenMultipleInner.kt

@@ -0,0 +1,47 @@
+sealed class Sealed() {
+    object First: Sealed()
+    open class NonFirst: Sealed() {
+        class NonSecond: NonFirst() {
+            object Third: Sealed()
+            class NonThird: Sealed() {
+                object Fourth: NonFirst()
+                class Fifth: Sealed()
+            }    
+        }
+        object Second: Sealed()
+    }    
+}
+
+fun foo(s: Sealed) = when(s) {
+    Sealed.First -> 1
+    is Sealed.NonFirst -> 2
+    Sealed.NonFirst.Second -> 4
+    Sealed.NonFirst.NonSecond.Third -> 6
+    is Sealed.NonFirst.NonSecond.NonThird -> 8
+    is Sealed.NonFirst.NonSecond.NonThird.Fifth -> 10
+    // no else required
+}
+
+fun fooWithElse(s: Sealed) = when(s) {
+    Sealed.First -> 1
+    Sealed.NonFirst.NonSecond.Third -> 6
+    is Sealed.NonFirst.NonSecond.NonThird.Fifth -> 10
+    else -> 0
+}
+
+fun fooWithoutElse(s: Sealed) = <!NO_ELSE_IN_WHEN!>when<!>(s) {
+    Sealed.First -> 1
+    is Sealed.NonFirst -> 2
+    Sealed.NonFirst.NonSecond.Third -> 6
+    is Sealed.NonFirst.NonSecond.NonThird -> 8
+    is Sealed.NonFirst.NonSecond.NonThird.Fifth -> 10
+}
+
+fun barWithoutElse(s: Sealed) = <!NO_ELSE_IN_WHEN!>when<!>(s) {
+    Sealed.First -> 1
+    is Sealed.NonFirst -> 2
+    Sealed.NonFirst.Second -> 4
+    is Sealed.NonFirst.NonSecond.NonThird -> 8
+    is Sealed.NonFirst.NonSecond.NonThird.Fifth -> 10
+}
+

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenMultipleInner.txt

@@ -0,0 +1,69 @@
+package
+
+internal fun barWithoutElse(/*0*/ s: Sealed): kotlin.Int
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+internal fun fooWithElse(/*0*/ s: Sealed): kotlin.Int
+internal fun fooWithoutElse(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal final class NonSecond : Sealed.NonFirst {
+            public constructor NonSecond()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+            internal final class NonThird : Sealed {
+                public constructor NonThird()
+                public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+                public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+                public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+                internal final class Fifth : Sealed {
+                    public constructor Fifth()
+                    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+                    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+                    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+                }
+
+                internal object Fourth : Sealed.NonFirst {
+                    private constructor Fourth()
+                    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+                    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+                    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+                }
+            }
+
+            internal object Third : Sealed {
+                private constructor Third()
+                public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+                public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+                public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+            }
+        }
+
+        internal object Second : Sealed {
+            private constructor Second()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenNegated.kt

@@ -0,0 +1,16 @@
+sealed class Sealed(val x: Int) {
+    object First: Sealed(12)
+    open class NonFirst(x: Int, val y: Int): Sealed(x) {
+        object Second: NonFirst(34, 2)
+        object Third: NonFirst(56, 3)
+    }
+}
+
+fun foo(s: Sealed): Int {
+    return when(s) {
+        is Sealed.First -> 1
+        !is Sealed.First -> 0
+        // no else required
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenNegated.txt

@@ -0,0 +1,46 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        internal final val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenNegatedTwice.kt

@@ -0,0 +1,17 @@
+sealed class Sealed(val x: Int) {
+    object First: Sealed(12)
+    open class NonFirst(x: Int, val y: Int): Sealed(x) {
+        object Second: NonFirst(34, 2)
+        object Third: NonFirst(56, 3)
+    }
+    object Last: Sealed(78)
+}
+
+fun foo(s: Sealed): Int {
+    return when(s) {
+        !is Sealed.First -> 1
+        !is Sealed.Last -> 0
+        // no else required
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenNegatedTwice.txt

@@ -0,0 +1,54 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal object Last : Sealed {
+        private constructor Last()
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        internal final val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenOnNestedSealed.kt

@@ -0,0 +1,20 @@
+sealed class Sealed {
+    object First: Sealed()
+    sealed class NonFirst {
+        object Second: NonFirst()
+        object Third: NonFirst()
+        object Fourth: Sealed()
+    }    
+}
+
+fun foo(s: Sealed, nf: Sealed.NonFirst): Int {
+    val si = when(s) {
+        Sealed.First -> 1
+        Sealed.NonFirst.Fourth -> 4
+    }
+    val nfi = when(nf) {
+        Sealed.NonFirst.Second -> 2
+        Sealed.NonFirst.Third -> 3
+    }
+    return si + nfi
+}

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenOnNestedSealed.txt

@@ -0,0 +1,45 @@
+package
+
+internal fun foo(/*0*/ s: Sealed, /*1*/ nf: Sealed.NonFirst): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal sealed class NonFirst {
+        public constructor NonFirst()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Fourth : Sealed {
+            private constructor Fourth()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenOnNullable.kt

@@ -0,0 +1,17 @@
+sealed class Sealed(val x: Int) {
+    object First: Sealed(12)
+    open class NonFirst(x: Int, val y: Int): Sealed(x) {
+        object Second: NonFirst(34, 2)
+        object Third: NonFirst(56, 3)
+    }
+}
+
+fun foo(s: Sealed?): Int {
+    return when(s) {
+        is Sealed.First -> 1
+        is Sealed.NonFirst -> 0
+        null -> -1
+        // no else required
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenOnNullable.txt

@@ -0,0 +1,46 @@
+package
+
+internal fun foo(/*0*/ s: Sealed?): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        internal final val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenWithAdditionalMember.kt

@@ -0,0 +1,18 @@
+sealed class Sealed(val x: Int) {
+    data class Tuple(val x: Int, val y: Int)
+    object First: Sealed(12)
+    open class NonFirst(tuple: Tuple): Sealed(tuple.x) {
+        val y: Int = tuple.y
+        object Second: NonFirst(Tuple(34, 2))
+        object Third: NonFirst(Tuple(56, 3))
+    }
+}
+
+fun foo(s: Sealed): Int {
+    return when(s) {
+        is Sealed.First -> 1
+        is Sealed.NonFirst -> 0
+        // no else required
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenWithAdditionalMember.txt

@@ -0,0 +1,58 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst(/*0*/ tuple: Sealed.Tuple)
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        internal final val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+
+    kotlin.data() internal final class Tuple {
+        public constructor Tuple(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int)
+        internal final val x: kotlin.Int
+        internal final val y: kotlin.Int
+        internal final /*synthesized*/ fun component1(): kotlin.Int
+        internal final /*synthesized*/ fun component2(): kotlin.Int
+        public final /*synthesized*/ fun copy(/*0*/ x: kotlin.Int = ..., /*1*/ y: kotlin.Int = ...): Sealed.Tuple
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenWithElse.kt

@@ -0,0 +1,15 @@
+sealed class Sealed(val x: Int) {
+    object First: Sealed(12)
+    open class NonFirst(x: Int, val y: Int): Sealed(x) {
+        object Second: NonFirst(34, 2)
+        object Third: NonFirst(56, 3)
+    }
+}
+
+fun foo(s: Sealed): Int {
+    return when(s) {
+        is Sealed.NonFirst -> 0
+        else -> -1
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/ExhaustiveWhenWithElse.txt

@@ -0,0 +1,46 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        internal final val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhen.kt

@@ -0,0 +1,14 @@
+sealed class Sealed(val x: Int) {
+    object First: Sealed(12)
+    open class NonFirst(x: Int, val y: Int): Sealed(x) {
+        object Second: NonFirst(34, 2)
+        object Third: NonFirst(56, 3)
+    }
+}
+
+fun foo(s: Sealed): Int {
+    return <!NO_ELSE_IN_WHEN!>when<!>(s) {
+        is Sealed.NonFirst -> 0
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhen.txt

@@ -0,0 +1,46 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        internal final val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhenNegated.kt

@@ -0,0 +1,14 @@
+sealed class Sealed(val x: Int) {
+    object First: Sealed(12)
+    open class NonFirst(x: Int, val y: Int): Sealed(x) {
+        object Second: NonFirst(34, 2)
+        object Third: NonFirst(56, 3)
+    }
+}
+
+fun foo(s: Sealed): Int {
+    return <!NO_ELSE_IN_WHEN!>when<!>(s) {
+        !is Sealed.NonFirst -> 1
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhenNegated.txt

@@ -0,0 +1,46 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        internal final val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal final override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhenWithAdditionalCase.kt

@@ -0,0 +1,22 @@
+sealed class Sealed(val x: Int) {
+    interface ITuple {
+        val x: Int
+        val y: Int
+    }
+    class Tuple(override val x: Int, override val y: Int): ITuple
+    object First: Sealed(12)
+    open class NonFirst(tuple: Tuple): Sealed(tuple.x), ITuple {
+        override val y: Int = tuple.y
+        object Second: NonFirst(Tuple(34, 2))
+        class Third: NonFirst(Tuple(56, 3))
+    }
+}
+
+fun foo(s: Sealed): Int {
+    return <!NO_ELSE_IN_WHEN!>when<!>(s) {
+        is Sealed.First -> 1
+        !is <!INCOMPATIBLE_TYPES!>Sealed.ITuple<!> -> 0
+        // else required
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhenWithAdditionalCase.txt

@@ -0,0 +1,63 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal interface ITuple {
+        internal abstract val x: kotlin.Int
+        internal abstract val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed, Sealed.ITuple {
+        public constructor NonFirst(/*0*/ tuple: Sealed.Tuple)
+        internal final override /*2*/ /*fake_override*/ val x: kotlin.Int
+        internal open override /*1*/ val y: kotlin.Int
+        public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal open override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal final class Third : Sealed.NonFirst {
+            public constructor Third()
+            internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
+            internal open override /*1*/ /*fake_override*/ val y: kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+
+    internal final class Tuple : Sealed.ITuple {
+        public constructor Tuple(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int)
+        internal open override /*1*/ val x: kotlin.Int
+        internal open override /*1*/ val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhenWithAnyCase.kt

@@ -0,0 +1,15 @@
+sealed class Sealed {
+    object First: Sealed()
+    open class NonFirst: Sealed() {
+        object Second: NonFirst()
+        object Third: NonFirst()
+    }
+}
+
+fun foo(s: Sealed): Int {
+    return <!NO_ELSE_IN_WHEN!>when<!>(s) {
+        is Sealed.First -> 1
+        !is Any -> 0
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhenWithAnyCase.txt

@@ -0,0 +1,38 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object First : Sealed {
+        private constructor First()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class NonFirst : Sealed {
+        public constructor NonFirst()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal object Second : Sealed.NonFirst {
+            private constructor Second()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal object Third : Sealed.NonFirst {
+            private constructor Third()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/OperationWhen.kt

@@ -0,0 +1,20 @@
+sealed class Operation(val left: Int, val right: Int) {
+    abstract fun exec(): Int
+    class Plus(left: Int, right: Int): Operation(left, right) {
+        override fun exec(): Int = left + right
+    }
+    class Minus(left: Int, right: Int): Operation(left, right) {
+        override fun exec(): Int = left - right
+    }
+    class Times(left: Int, right: Int): Operation(left, right) {
+        override fun exec(): Int = left * right
+    }
+    class Slash(left: Int, right: Int): Operation(left, right) {
+        override fun exec(): Int = left / right
+    }
+}
+
+fun priority(op: Operation) = when(op) {
+    is Operation.Plus, is Operation.Minus  -> 1
+    is Operation.Times, is Operation.Slash -> 2
+}

compiler/testData/diagnostics/tests/sealed/OperationWhen.txt

@@ -0,0 +1,53 @@
+package
+
+internal fun priority(/*0*/ op: Operation): kotlin.Int
+
+internal sealed class Operation {
+    public constructor Operation(/*0*/ left: kotlin.Int, /*1*/ right: kotlin.Int)
+    internal final val left: kotlin.Int
+    internal final val right: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    internal abstract fun exec(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal final class Minus : Operation {
+        public constructor Minus(/*0*/ left: kotlin.Int, /*1*/ right: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val left: kotlin.Int
+        internal final override /*1*/ /*fake_override*/ val right: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        internal open override /*1*/ fun exec(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final class Plus : Operation {
+        public constructor Plus(/*0*/ left: kotlin.Int, /*1*/ right: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val left: kotlin.Int
+        internal final override /*1*/ /*fake_override*/ val right: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        internal open override /*1*/ fun exec(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final class Slash : Operation {
+        public constructor Slash(/*0*/ left: kotlin.Int, /*1*/ right: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val left: kotlin.Int
+        internal final override /*1*/ /*fake_override*/ val right: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        internal open override /*1*/ fun exec(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final class Times : Operation {
+        public constructor Times(/*0*/ left: kotlin.Int, /*1*/ right: kotlin.Int)
+        internal final override /*1*/ /*fake_override*/ val left: kotlin.Int
+        internal final override /*1*/ /*fake_override*/ val right: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        internal open override /*1*/ fun exec(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}

compiler/testData/diagnostics/tests/sealed/TreeWhen.kt

@@ -0,0 +1,13 @@
+sealed class Tree {
+    object Empty: Tree()
+    class Leaf(val x: Int): Tree()
+    class Node(val left: Tree, val right: Tree): Tree()
+
+    fun max(): Int {
+        when(this) {
+            is Empty -> return -1
+            is Leaf -> return <!DEBUG_INFO_SMARTCAST!>this<!>.x
+            is Node -> return <!DEBUG_INFO_SMARTCAST!>this<!>.left.max()
+        }
+    }
+}

compiler/testData/diagnostics/tests/sealed/TreeWhen.txt

@@ -0,0 +1,36 @@
+package
+
+internal sealed class Tree {
+    public constructor Tree()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    internal final fun max(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object Empty : Tree {
+        private constructor Empty()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun max(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final class Leaf : Tree {
+        public constructor Leaf(/*0*/ x: kotlin.Int)
+        internal final val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun max(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final class Node : Tree {
+        public constructor Node(/*0*/ left: Tree, /*1*/ right: Tree)
+        internal final val left: Tree
+        internal final val right: Tree
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun max(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}

compiler/testData/diagnostics/tests/sealed/TreeWhenFunctional.kt

@@ -0,0 +1,11 @@
+sealed class Tree {
+    object Empty: Tree()
+    class Leaf(val x: Int): Tree()
+    class Node(val left: Tree, val right: Tree): Tree()
+
+    fun max(): Int = when(this) {
+        is Empty -> -1
+        is Leaf  -> <!DEBUG_INFO_SMARTCAST!>this<!>.x
+        is Node  -> <!DEBUG_INFO_SMARTCAST!>this<!>.left.max()
+    }
+}

compiler/testData/diagnostics/tests/sealed/TreeWhenFunctional.txt

@@ -0,0 +1,36 @@
+package
+
+internal sealed class Tree {
+    public constructor Tree()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    internal final fun max(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object Empty : Tree {
+        private constructor Empty()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun max(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final class Leaf : Tree {
+        public constructor Leaf(/*0*/ x: kotlin.Int)
+        internal final val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun max(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final class Node : Tree {
+        public constructor Node(/*0*/ left: Tree, /*1*/ right: Tree)
+        internal final val left: Tree
+        internal final val right: Tree
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun max(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}

compiler/testData/diagnostics/tests/sealed/TreeWhenFunctionalNoIs.kt

@@ -0,0 +1,23 @@
+sealed class Tree {
+    object Empty: Tree()
+    class Leaf(val x: Int): Tree()
+    class Node(val left: Tree, val right: Tree): Tree()
+
+    fun max(): Int = when(this) {
+        Empty -> -1
+        is Leaf  -> <!DEBUG_INFO_SMARTCAST!>this<!>.x
+        is Node  -> <!DEBUG_INFO_SMARTCAST!>this<!>.left.max()
+    }
+
+    fun maxIsClass(): Int = <!NO_ELSE_IN_WHEN!>when<!>(this) {
+        Empty -> -1
+        <!NO_COMPANION_OBJECT!>Leaf<!>  -> 0
+        is Node  -> <!DEBUG_INFO_SMARTCAST!>this<!>.left.max()
+    }
+
+    fun maxWithElse(): Int = when(this) {
+        is Leaf  -> <!DEBUG_INFO_SMARTCAST!>this<!>.x
+        is Node  -> <!DEBUG_INFO_SMARTCAST!>this<!>.left.max()
+        else -> -1
+    }
+}

compiler/testData/diagnostics/tests/sealed/TreeWhenFunctionalNoIs.txt

@@ -0,0 +1,44 @@
+package
+
+internal sealed class Tree {
+    public constructor Tree()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    internal final fun max(): kotlin.Int
+    internal final fun maxIsClass(): kotlin.Int
+    internal final fun maxWithElse(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object Empty : Tree {
+        private constructor Empty()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun max(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun maxIsClass(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun maxWithElse(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final class Leaf : Tree {
+        public constructor Leaf(/*0*/ x: kotlin.Int)
+        internal final val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun max(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun maxIsClass(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun maxWithElse(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final class Node : Tree {
+        public constructor Node(/*0*/ left: Tree, /*1*/ right: Tree)
+        internal final val left: Tree
+        internal final val right: Tree
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun max(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun maxIsClass(): kotlin.Int
+        internal final override /*1*/ /*fake_override*/ fun maxWithElse(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}

compiler/testData/diagnostics/tests/sealed/WhenOnEmptySealed.kt

@@ -0,0 +1,11 @@
+// !DIAGNOSTICS: -UNUSED_EXPRESSION
+sealed class Sealed {
+
+}
+
+fun foo(s: Sealed): Int {
+    return <!NO_ELSE_IN_WHEN!>when<!>(s) {
+        // We do not return anything, so else branch must be here
+    }
+}
+

compiler/testData/diagnostics/tests/sealed/WhenOnEmptySealed.txt

@@ -0,0 +1,10 @@
+package
+
+internal fun foo(/*0*/ s: Sealed): kotlin.Int
+
+internal sealed class Sealed {
+    public constructor Sealed()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}