dfa: don't suggest to replace reference qualifiers with null

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

@@ -291,7 +291,7 @@ public class DataFlowInspectionBase extends BaseJavaBatchLocalInspectionTool {
   private static void reportConstantReferenceValues(ProblemsHolder holder, StandardInstructionVisitor visitor, Set<PsiElement> reportedAnchors) {
     for (Pair<PsiReferenceExpression, DfaConstValue> pair : visitor.getConstantReferenceValues()) {
       PsiReferenceExpression ref = pair.first;
-      if (!reportedAnchors.add(ref)) {
+      if (ref.getParent() instanceof PsiReferenceExpression || !reportedAnchors.add(ref)) {
         continue;
       }
 

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

@@ -16,4 +16,10 @@ class Test {
     return foo;
   }
 
+  public void testDontReplaceQualifierWithNull(Object bar) {
+    if (bar == null) {
+      <warning descr="Method invocation 'bar.hashCode()' may produce 'java.lang.NullPointerException'">bar.hashCode()</warning>;
+    }
+  }
+
 }

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

@@ -16,4 +16,10 @@ class Test {
     return foo;
   }
 
+  public void testDontReplaceQualifierWithNull(Object bar) {
+    if (bar == null) {
+      bar.hashCode();
+    }
+  }
+
 }