[FIR LT] Fix crash in incomplete when condition without type

#KT-58908 Fixed

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFirTestdataTestGenerated.java

@@ -3817,6 +3817,12 @@ public class DiagnosticCompilerTestFirTestdataTestGenerated extends AbstractDiag
                 runTest("compiler/fir/analysis-tests/testData/resolve/problems/incompleteUserTypeWithUnresovledTypeArgument.kt");
             }
 
+            @Test
+            @TestMetadata("incompleteWhen.kt")
+            public void testIncompleteWhen() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolve/problems/incompleteWhen.kt");
+            }
+
             @Test
             @TestMetadata("innerClassHierarchy.kt")
             public void testInnerClassHierarchy() throws Exception {

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFirTestDataTestGenerated.java

@@ -3817,6 +3817,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFirTestDataTestGenerated
                 runTest("compiler/fir/analysis-tests/testData/resolve/problems/incompleteUserTypeWithUnresovledTypeArgument.kt");
             }
 
+            @Test
+            @TestMetadata("incompleteWhen.kt")
+            public void testIncompleteWhen() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolve/problems/incompleteWhen.kt");
+            }
+
             @Test
             @TestMetadata("innerClassHierarchy.kt")
             public void testInnerClassHierarchy() throws Exception {

compiler/fir/analysis-tests/legacy-fir-tests/tests-gen/org/jetbrains/kotlin/fir/LazyBodyIsNotTouchedTestGenerated.java

@@ -3356,6 +3356,11 @@ public class LazyBodyIsNotTouchedTestGenerated extends AbstractLazyBodyIsNotTouc
             runTest("compiler/fir/analysis-tests/testData/resolve/problems/incompleteUserTypeWithUnresovledTypeArgument.kt");
         }
 
+        @TestMetadata("incompleteWhen.kt")
+        public void testIncompleteWhen() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/resolve/problems/incompleteWhen.kt");
+        }
+
         @TestMetadata("innerClassHierarchy.kt")
         public void testInnerClassHierarchy() throws Exception {
             runTest("compiler/fir/analysis-tests/testData/resolve/problems/innerClassHierarchy.kt");

compiler/fir/analysis-tests/testData/resolve/problems/incompleteWhen.fir.txt

@@ -0,0 +1,9 @@
+FILE: incompleteWhen.kt
+    public final fun main(args: R|kotlin/Array<kotlin/String>|): R|kotlin/Unit| {
+        lval x: R|kotlin/Int| = Int(42)
+        when (R|<local>/x|) {
+            ($subj$ is <ERROR TYPE REF: Incomplete code>) ->  {
+            }
+        }
+
+    }

compiler/fir/analysis-tests/testData/resolve/problems/incompleteWhen.kt

@@ -0,0 +1,4 @@
+fun main(args: Array<String>) {
+    val x = 42
+    when (x) {is<!SYNTAX!><!>}
+}

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeDiagnosticsTestGenerated.java

@@ -3817,6 +3817,12 @@ public class FirLightTreeDiagnosticsTestGenerated extends AbstractFirLightTreeDi
                 runTest("compiler/fir/analysis-tests/testData/resolve/problems/incompleteUserTypeWithUnresovledTypeArgument.kt");
             }
 
+            @Test
+            @TestMetadata("incompleteWhen.kt")
+            public void testIncompleteWhen() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolve/problems/incompleteWhen.kt");
+            }
+
             @Test
             @TestMetadata("innerClassHierarchy.kt")
             public void testInnerClassHierarchy() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiDiagnosticTestGenerated.java

@@ -3817,6 +3817,12 @@ public class FirPsiDiagnosticTestGenerated extends AbstractFirPsiDiagnosticTest
                 runTest("compiler/fir/analysis-tests/testData/resolve/problems/incompleteUserTypeWithUnresovledTypeArgument.kt");
             }
 
+            @Test
+            @TestMetadata("incompleteWhen.kt")
+            public void testIncompleteWhen() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolve/problems/incompleteWhen.kt");
+            }
+
             @Test
             @TestMetadata("innerClassHierarchy.kt")
             public void testInnerClassHierarchy() throws Exception {

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

@@ -45,6 +45,7 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirValueParameterSymbol
 import org.jetbrains.kotlin.fir.types.FirTypeProjection
 import org.jetbrains.kotlin.fir.types.FirTypeRef
+import org.jetbrains.kotlin.fir.types.builder.buildErrorTypeRef
 import org.jetbrains.kotlin.lexer.KtTokens.*
 import org.jetbrains.kotlin.name.CallableId
 import org.jetbrains.kotlin.name.SpecialNames
@@ -912,7 +913,7 @@ class ExpressionsConverter(
         hasSubject: Boolean,
     ): WhenConditionConvertedResults {
         lateinit var firOperation: FirOperation
-        lateinit var firType: FirTypeRef
+        var firType: FirTypeRef? = null
         whenCondition.forEachChildren {
             when (it.tokenType) {
                 TYPE_REFERENCE -> firType = declarationsConverter.convertType(it)
@@ -929,7 +930,7 @@ class ExpressionsConverter(
         val result = buildTypeOperatorCall {
             source = whenCondition.toFirSourceElement()
             operation = firOperation
-            conversionTypeRef = firType
+            conversionTypeRef = firType ?: buildErrorTypeRef { diagnostic = ConeSyntaxDiagnostic("Incomplete code") }
             argumentList = buildUnaryArgumentList(subjectExpression)
         }