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

^KT-50028 Fixed

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()
+    }
+  }
+}