[FIR] Unwrap flexible types in when exhaustiveness checker

^KT-56942 Fixed

compiler/testData/diagnostics/tests/testsWithJava17/sealedClasses/flexibleSealedInSubject.fir.kt

@@ -0,0 +1,59 @@
+// ISSUE: KT-56942
+// FILE: Base.java
+public sealed class Base permits A, B {
+    public static Base provide() { return new A(); }
+}
+
+// FILE: A.java
+public final class A extends Base {}
+
+// FILE: B.java
+public final class B extends Base {}
+
+// FILE: main.kt
+
+fun test_0(base: Base) {
+    <!NO_ELSE_IN_WHEN!>when<!> (base) {
+
+    }
+
+    when (base) {
+        is A -> {}
+        is B -> {}
+    }
+
+    when (base) {
+        is A -> {}
+        is B -> {}
+        <!SENSELESS_NULL_IN_WHEN!>null<!> -> {}
+    }
+
+    when (base) {
+        is A -> {}
+        is B -> {}
+        else -> {}
+    }
+}
+
+fun test_1() {
+    <!NO_ELSE_IN_WHEN!>when<!> (Base.provide()) {
+
+    }
+
+    when (Base.provide()) {
+        is A -> {}
+        is B -> {}
+    }
+
+    when (Base.provide()) {
+        is A -> {}
+        is B -> {}
+        null -> {}
+    }
+
+    when (Base.provide()) {
+        is A -> {}
+        is B -> {}
+        else -> {}
+    }
+}

compiler/testData/diagnostics/tests/testsWithJava17/sealedClasses/flexibleSealedInSubject.kt

@@ -0,0 +1,59 @@
+// ISSUE: KT-56942
+// FILE: Base.java
+public sealed class Base permits A, B {
+    public static Base provide() { return new A(); }
+}
+
+// FILE: A.java
+public final class A extends Base {}
+
+// FILE: B.java
+public final class B extends Base {}
+
+// FILE: main.kt
+
+fun test_0(base: Base) {
+    <!NO_ELSE_IN_WHEN!>when<!> (base) {
+
+    }
+
+    when (base) {
+        is A -> {}
+        is B -> {}
+    }
+
+    when (base) {
+        is A -> {}
+        is B -> {}
+        <!SENSELESS_NULL_IN_WHEN!>null<!> -> {}
+    }
+
+    when (base) {
+        is A -> {}
+        is B -> {}
+        <!REDUNDANT_ELSE_IN_WHEN!>else<!> -> {}
+    }
+}
+
+fun test_1() {
+    <!NO_ELSE_IN_WHEN!>when<!> (Base.provide()) {
+
+    }
+
+    when (Base.provide()) {
+        is A -> {}
+        is B -> {}
+    }
+
+    when (Base.provide()) {
+        is A -> {}
+        is B -> {}
+        null -> {}
+    }
+
+    when (Base.provide()) {
+        is A -> {}
+        is B -> {}
+        else -> {}
+    }
+}

compiler/testData/diagnostics/tests/when/flexibleEnumInSubject.kt

@@ -0,0 +1,51 @@
+// FIR_IDENTICAL
+// ISSUE: KT-56942
+// FILE: EnumJava.java
+public enum EnumJava {
+    JAVA_ONE, JAVA_TWO;
+
+    public static EnumJava provide() { return EnumJava.JAVA_ONE; }
+}
+
+// FILE: EnumProviderJava.java
+public class EnumProviderJava {
+    public static EnumJava provide() { return EnumJava.JAVA_ONE; }
+}
+
+
+// FILE: main.kt
+enum class EnumKotlin {
+    KOTLIN_ONE, KOTLIN_TWO;
+
+    companion object {
+        fun provide(): EnumKotlin = EnumKotlin.KOTLIN_ONE
+    }
+}
+
+fun test_1(ejp: EnumJava, ekp: EnumKotlin) {
+    <!NO_ELSE_IN_WHEN!>when<!> (ejp) {
+        EnumJava.JAVA_ONE -> {}
+    }
+
+    <!NO_ELSE_IN_WHEN!>when<!> (ekp) {
+        EnumKotlin.KOTLIN_ONE -> {}
+    }
+
+    <!NO_ELSE_IN_WHEN!>when<!> (EnumJava.provide()) {
+        EnumJava.JAVA_ONE -> {}
+    }
+
+    <!NO_ELSE_IN_WHEN!>when<!> (EnumKotlin.provide()) {
+        EnumKotlin.KOTLIN_ONE -> {}
+    }
+}
+
+fun test_2(ejp: EnumJava, ekp: EnumKotlin) {
+    <!NO_ELSE_IN_WHEN!>when<!> (ejp) {}
+
+    <!NO_ELSE_IN_WHEN!>when<!> (ekp) {}
+
+    <!NO_ELSE_IN_WHEN!>when<!> (EnumProviderJava.provide()) {}
+
+    <!NO_ELSE_IN_WHEN!>when<!> (EnumKotlin.provide()) {}
+}