[java-dfa] Switching on expression of unknown type should not mark branches as unreachable

Fixes IDEA-371191 Unhelpful "unreachable switch label" warning

GitOrigin-RevId: d3e92efc518590ed7c5b7219b9ba0378c292507d

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/ControlFlowAnalyzer.java

@@ -979,7 +979,8 @@ public class ControlFlowAnalyzer extends JavaElementVisitor {
       }
       selector.accept(this);
       if (syntheticVar) {
-        expressionValue = createTempVariable(targetType);
+        expressionValue = targetType == null ? 
+                          myCurrentFlow.createTempVariable(DfType.TOP) : createTempVariable(targetType);
         addInstruction(new SimpleAssignmentInstruction(null, expressionValue));
       }
       addInstruction(new PopInstruction());

java/java-tests/testData/inspection/dataFlow/fixture/SwitchNoUnreachableBranchesDueToUnresolvedType.java

@@ -0,0 +1,11 @@
+enum E {
+  A, B, C;
+
+  int x(E e, String s) {
+    return switch (<error descr="Cannot resolve symbol 'd'">d</error>) {
+      case A -> 1;
+      case B -> 2;
+      case C -> 3;
+    };
+  }
+}

java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection21Test.java

@@ -184,4 +184,8 @@ public class DataFlowInspection21Test extends DataFlowInspectionTestCase {
     DataFlowInspectionTest.addJavaxNullabilityAnnotations(myFixture);
     doTest();
   }
+  
+  public void testSwitchNoUnreachableBranchesDueToUnresolvedType() {
+    doTest();
+  }
 }