[FE 1.0] Correctly set USED_AS_EXPRESSION for unreachable when and if blocks

^KT-50028 Fixed

compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/ir/Fir2IrTextTestGenerated.java

@@ -1658,6 +1658,12 @@ public class Fir2IrTextTestGenerated extends AbstractFir2IrTextTest {
             runTest("compiler/testData/ir/irText/expressions/kt49203.kt");
         }
 
+        @Test
+        @TestMetadata("kt50028.kt")
+        public void testKt50028() throws Exception {
+            runTest("compiler/testData/ir/irText/expressions/kt50028.kt");
+        }
+
         @Test
         @TestMetadata("lambdaInCAO.kt")
         public void testLambdaInCAO() throws Exception {

compiler/frontend/cfg/src/org/jetbrains/kotlin/cfg/ControlFlowInformationProviderImpl.kt

@@ -812,17 +812,33 @@ class ControlFlowInformationProviderImpl private constructor(
             for (element in pseudocode.getValueElements(value)) {
                 trace.record(USED_AS_EXPRESSION, element, isUsedAsExpression)
                 trace.record(USED_AS_RESULT_OF_LAMBDA, element, isUsedAsResultOfLambda)
-                if (isUsedAsExpression && element is KtTryExpression) {
-                    trace.record(USED_AS_EXPRESSION, element.tryBlock, true)
-                    for (catchClause in element.catchClauses) {
-                        val body = catchClause.catchBody ?: continue
-                        trace.record(USED_AS_EXPRESSION, body, true)
+                if (isUsedAsExpression) {
+                    when (element) {
+                        is KtTryExpression -> {
+                            element.tryBlock.recordUsedAsExpression()
+                            for (catchClause in element.catchClauses) {
+                                catchClause.catchBody?.recordUsedAsExpression()
+                            }
+                        }
+                        is KtIfExpression -> {
+                            (element.then as? KtBlockExpression)?.recordUsedAsExpression()
+                            (element.`else` as? KtBlockExpression)?.recordUsedAsExpression()
+                        }
+                        is KtWhenExpression -> {
+                            for (entry in element.entries) {
+                                (entry.expression as? KtBlockExpression)?.recordUsedAsExpression()
+                            }
+                        }
                     }
                 }
             }
         }
     }
 
+    private fun KtExpression.recordUsedAsExpression() {
+        trace.record(USED_AS_EXPRESSION, this, true)
+    }
+
     private fun checkForSuspendLambdaAndMarkParameters(pseudocode: Pseudocode) {
         for (instruction in pseudocode.instructionsIncludingDeadCode) {
             if (instruction is LocalFunctionDeclarationInstruction) {

compiler/testData/codegen/box/controlStructures/returnsNothing/ifElse.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: WASM
-// WASM_MUTE_REASON: STRANGE_IMPLICIT_CAST
-
 fun kt49182(x: Boolean): String {
     return if (x) {
         return "O"
@@ -23,4 +20,4 @@ fun box(): String {
         exit()
     }
     return a
-}
+}

compiler/testData/ir/irText/expressions/kt50028.fir.ir.txt

@@ -0,0 +1,21 @@
+FILE fqName:<root> fileName:/kt50028.kt
+  FUN name:test_1 visibility:public modality:FINAL <> () returnType:kotlin.String
+    BLOCK_BODY
+      RETURN type=kotlin.Nothing from='public final fun test_1 (): kotlin.String declared in <root>'
+        WHEN type=kotlin.Nothing origin=WHEN
+          BRANCH
+            if: CONST Boolean type=kotlin.Boolean value=true
+            then: RETURN type=kotlin.Nothing from='public final fun test_1 (): kotlin.String declared in <root>'
+              CONST String type=kotlin.String value=""
+  FUN name:test_2 visibility:public modality:FINAL <> (b:kotlin.Boolean) returnType:kotlin.Boolean
+    VALUE_PARAMETER name:b index:0 type:kotlin.Boolean
+    BLOCK_BODY
+      RETURN type=kotlin.Nothing from='public final fun test_2 (b: kotlin.Boolean): kotlin.Boolean declared in <root>'
+        WHEN type=kotlin.Boolean origin=IF
+          BRANCH
+            if: GET_VAR 'b: kotlin.Boolean declared in <root>.test_2' type=kotlin.Boolean origin=null
+            then: CONST Boolean type=kotlin.Boolean value=true
+          BRANCH
+            if: CONST Boolean type=kotlin.Boolean value=true
+            then: THROW type=kotlin.Nothing
+              CONSTRUCTOR_CALL 'public constructor <init> (message: kotlin.String) [primary] declared in kotlin.NotImplementedError' type=kotlin.NotImplementedError origin=null

compiler/testData/ir/irText/expressions/kt50028.fir.kt.txt

@@ -0,0 +1,12 @@
+fun test_1(): String {
+  return when {
+    else -> return ""
+  }
+}
+
+fun test_2(b: Boolean): Boolean {
+  return when {
+    b -> true
+    else -> throw NotImplementedError()
+  }
+}

compiler/testData/ir/irText/expressions/kt50028.ir.txt

@@ -0,0 +1,24 @@
+FILE fqName:<root> fileName:/kt50028.kt
+  FUN name:test_1 visibility:public modality:FINAL <> () returnType:kotlin.String
+    BLOCK_BODY
+      RETURN type=kotlin.Nothing from='public final fun test_1 (): kotlin.String declared in <root>'
+        WHEN type=kotlin.String origin=WHEN
+          BRANCH
+            if: CONST Boolean type=kotlin.Boolean value=true
+            then: BLOCK type=kotlin.Nothing origin=null
+              RETURN type=kotlin.Nothing from='public final fun test_1 (): kotlin.String declared in <root>'
+                CONST String type=kotlin.String value=""
+  FUN name:test_2 visibility:public modality:FINAL <> (b:kotlin.Boolean) returnType:kotlin.Boolean
+    VALUE_PARAMETER name:b index:0 type:kotlin.Boolean
+    BLOCK_BODY
+      RETURN type=kotlin.Nothing from='public final fun test_2 (b: kotlin.Boolean): kotlin.Boolean declared in <root>'
+        WHEN type=kotlin.Boolean origin=IF
+          BRANCH
+            if: GET_VAR 'b: kotlin.Boolean declared in <root>.test_2' type=kotlin.Boolean origin=null
+            then: BLOCK type=kotlin.Boolean origin=null
+              CONST Boolean type=kotlin.Boolean value=true
+          BRANCH
+            if: CONST Boolean type=kotlin.Boolean value=true
+            then: BLOCK type=kotlin.Nothing origin=null
+              THROW type=kotlin.Nothing
+                CONSTRUCTOR_CALL 'public constructor <init> (message: kotlin.String) [primary] declared in kotlin.NotImplementedError' type=kotlin.NotImplementedError origin=null

compiler/testData/ir/irText/expressions/kt50028.kt

@@ -0,0 +1,17 @@
+// ISSUE: KT-50028
+
+fun test_1(): String {
+    return when {
+        else -> {
+            return ""
+        }
+    }
+}
+
+fun test_2(b: Boolean): Boolean {
+    return if (b) {
+        true
+    } else {
+        throw NotImplementedError()
+    }
+}

compiler/testData/ir/irText/expressions/kt50028.kt.txt

@@ -0,0 +1,18 @@
+fun test_1(): String {
+  return when {
+    else -> { // BLOCK
+      return ""
+    }
+  }
+}
+
+fun test_2(b: Boolean): Boolean {
+  return when {
+    b -> { // BLOCK
+      true
+    }
+    else -> { // BLOCK
+      throw NotImplementedError()
+    }
+  }
+}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/ir/IrTextTestGenerated.java

@@ -1658,6 +1658,12 @@ public class IrTextTestGenerated extends AbstractIrTextTest {
             runTest("compiler/testData/ir/irText/expressions/kt49203.kt");
         }
 
+        @Test
+        @TestMetadata("kt50028.kt")
+        public void testKt50028() throws Exception {
+            runTest("compiler/testData/ir/irText/expressions/kt50028.kt");
+        }
+
         @Test
         @TestMetadata("lambdaInCAO.kt")
         public void testLambdaInCAO() throws Exception {

compiler/tests-gen/org/jetbrains/kotlin/ir/KlibTextTestCaseGenerated.java

@@ -1247,6 +1247,11 @@ public class KlibTextTestCaseGenerated extends AbstractKlibTextTestCase {
             runTest("compiler/testData/ir/irText/expressions/kt49203.kt");
         }
 
+        @TestMetadata("kt50028.kt")
+        public void testKt50028() throws Exception {
+            runTest("compiler/testData/ir/irText/expressions/kt50028.kt");
+        }
+
         @TestMetadata("lambdaInCAO.kt")
         public void testLambdaInCAO() throws Exception {
             runTest("compiler/testData/ir/irText/expressions/lambdaInCAO.kt");