when a nullable parameter is reassigned with an unknown value, don't still consider it nullable (IDEA-54770)

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

@@ -277,6 +277,7 @@ public class DfaMemoryStateImpl implements DfaMemoryState {
       applyCondition(compareToNull(var, true));
     }
     else if (value instanceof DfaTypeValue) {
+      getVariableState(var).setNullable(((DfaTypeValue)value).isNullable());
       DfaRelationValue dfaInstanceof = myFactory.getRelationFactory().createRelation(var, value, JavaTokenType.INSTANCEOF_KEYWORD, false);
       applyInstanceofOrNull(dfaInstanceof);
     }

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

@@ -0,0 +1,12 @@
+import org.jetbrains.annotations.Nullable;
+
+public class BrokenAlignment {
+
+  String unknown(String s) { return s; }
+
+  public void example(@Nullable String value) {
+    value = unknown(<warning descr="Argument 'value' might be null but passed to non annotated parameter">value</warning>);
+    if (value.contains("%")) {
+    }
+  }
+}

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

@@ -83,4 +83,6 @@ public class DataFlowInspectionFixtureTest extends JavaCodeInsightFixtureTestCas
   public void testFinalFieldsDifferentInstances() throws Throwable { doTest(); }
   public void testChainedFinalFieldAccessorsDfa() throws Throwable { doTest(); }
 
+  public void testAssigningUnknownToNullable() throws Throwable { doTest(); }
+
 }