dfa: variables shouldn't be marked unknown if they don't have known constant values

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

@@ -815,22 +815,36 @@ public class DfaMemoryStateImpl implements DfaMemoryState {
 
   @Override
   public void flushFields() {
+    Set<DfaVariableValue> vars = ContainerUtil.newLinkedHashSet(getChangedVariables());
     for (EqClass aClass : myEqClasses) {
       if (aClass != null) {
-        for (DfaVariableValue value : aClass.getVariables()) {
-          if (value.isFlushableByCalls()) {
-            doFlush(value, true);
-          }
-        }
+        vars.addAll(aClass.getVariables());
       }
     }
-    for (DfaVariableValue value : new ArrayList<DfaVariableValue>(getChangedVariables())) {
+    for (DfaVariableValue value : vars) {
       if (value.isFlushableByCalls()) {
-        doFlush(value, true);
+        doFlush(value, shouldMarkUnknown(value));
       }
     }
   }
 
+  private boolean shouldMarkUnknown(DfaVariableValue value) {
+    int eqClassIndex = getEqClassIndex(value);
+    if (eqClassIndex < 0) return false;
+
+    EqClass eqClass = myEqClasses.get(eqClassIndex);
+    if (eqClass == null) return false;
+    if (eqClass.findConstant(true) != null) return true;
+
+    for (UnorderedPair<EqClass> pair : getDistinctClassPairs()) {
+      if (pair.first == eqClass && pair.second.findConstant(true) != null ||
+          pair.second == eqClass && pair.first.findConstant(true) != null) {
+        return true;
+      }
+    }
+    return false;
+  }
+
   Set<DfaVariableValue> getChangedVariables() {
     return myVariableStates.keySet();
   }

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

@@ -305,6 +305,8 @@ public class DataFlowInspectionTest extends LightCodeInsightFixtureTestCase {
   public void testNotEqualsTypo() { doTest(); }
   public void testAndEquals() { doTest(); }
 
+  public void testUnusedCallDoesNotMakeUnknown() { doTest(); }
+
   public void testParametersAreNonnullByDefault() {
     myFixture.addClass("package javax.annotation; public @interface ParametersAreNonnullByDefault {}");
     myFixture.addClass("package javax.annotation; public @interface ParametersAreNullableByDefault {}");