IDEA-129040 Check for the string being not null in switch label.

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

@@ -591,12 +591,14 @@ public class ControlFlowAnalyzer extends JavaElementVisitor {
 
       generateBoxingUnboxingInstructionFor(caseExpression, PsiType.INT);
       final PsiClass psiClass = PsiUtil.resolveClassInType(caseExpression.getType());
-      if (psiClass != null && psiClass.isEnum()) {
+      if (psiClass != null) {
         addInstruction(new FieldReferenceInstruction(caseExpression, "switch statement expression"));
-        enumValues = new HashSet<PsiEnumConstant>();
-        for (PsiField f : psiClass.getFields()) {
-          if (f instanceof PsiEnumConstant) {
-            enumValues.add((PsiEnumConstant)f);
+        if (psiClass.isEnum()) {
+          enumValues = new HashSet<PsiEnumConstant>();
+          for (PsiField f : psiClass.getFields()) {
+            if (f instanceof PsiEnumConstant) {
+              enumValues.add((PsiEnumConstant)f);
+            }
           }
         }
       } else {

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

@@ -0,0 +1,10 @@
+import org.jetbrains.annotations.Nullable;
+
+class BrokenAlignment {
+
+  void test(@Nullable String n) {
+    switch (<warning descr="Dereference of 'n' may produce 'java.lang.NullPointerException'">n</warning>) {
+
+    }
+  }
+}

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

@@ -109,6 +109,7 @@ public class DataFlowInspectionTest extends LightCodeInsightFixtureTestCase {
   public void testAssigningClassLiteralToNullable() throws Throwable { doTest(); }
 
   public void testSynchronizingOnNullable() throws Throwable { doTest(); }
+  public void testSwitchOnNullable() { doTest(); }
   public void testReturningNullFromVoidMethod() throws Throwable { doTest(); }
 
   public void testCatchRuntimeException() throws Throwable { doTest(); }