[java-inspections] IDEA-332812 Convert to old-style switch: produce incorrect code for null, default

GitOrigin-RevId: f0de0aee91d2b41e1ebb6e7a815851cbbf5b8447

java/java-impl-inspections/src/com/intellij/codeInspection/EnhancedSwitchBackwardMigrationInspection.java

@@ -286,7 +286,11 @@ public final class EnhancedSwitchBackwardMigrationInspection extends AbstractBas
       }
       else {
         PsiCaseLabelElement[] labelElements = labelElementList.getElements();
-        caseExpressionsText = StreamEx.of(labelElements).map(e -> "case " + ct.text(e) + ":").joining("\n");
+        caseExpressionsText = StreamEx.of(labelElements)
+          .map(e -> e instanceof PsiDefaultCaseLabelElement ?
+                    (ct.text(e) + ":") :
+                    ("case " + ct.text(e) + ":"))
+          .joining("\n");
       }
       PsiStatement body = rule.getBody();
       String finalBody;

java/java-tests/testData/inspection/switchExpressionBackwardMigration/afterCaseNullDefault.java

@@ -0,0 +1,12 @@
+// "Replace with old style 'switch' statement" "true"
+
+class CaseNullDefault {
+  void bar(Object o) {
+      switch (o) {
+          case null:
+          default:
+              System.out.println("1");
+              break;
+      }
+  }
+}

java/java-tests/testData/inspection/switchExpressionBackwardMigration/afterReturnCaseNullDefault.java

@@ -0,0 +1,11 @@
+// "Replace with old style 'switch' statement" "true"
+
+class ReturnCaseNullDefault {
+  int bar(Object o) {
+      switch (o) {
+          case null:
+          default:
+              return 1;
+      }
+  }
+}

java/java-tests/testData/inspection/switchExpressionBackwardMigration/beforeCaseNullDefault.java

@@ -0,0 +1,9 @@
+// "Replace with old style 'switch' statement" "true"
+
+class CaseNullDefault {
+  void bar(Object o) {
+    switc<caret>h (o) {
+      case null, default -> System.out.println("1");
+    }
+  }
+}

java/java-tests/testData/inspection/switchExpressionBackwardMigration/beforeReturnCaseNullDefault.java

@@ -0,0 +1,9 @@
+// "Replace with old style 'switch' statement" "true"
+
+class ReturnCaseNullDefault {
+  int bar(Object o) {
+    return switc<caret>h (o) {
+      case null, default -> 1;
+    }
+  }
+}