IDEA-146131 @NotNull on parameters should only apply until reassignment

java/java-tests/testData/inspection/dataFlow/NotNullLocalVariable/expected.xml

@@ -1,8 +1,3 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <problems>
-  <problem>
-    <file>Npe.java</file>
-    <line>7</line>
-    <description>Condition 'o == null' is always false</description>
-  </problem>
 </problems>

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

@@ -0,0 +1,33 @@
+import org.jetbrains.annotations.*;
+
+class Test {
+
+  @Nullable
+  String findMessage(@NotNull Element element) {
+    while (element != null) {
+      if (element.getMessage() != null) {
+        return element.getMessage();
+      }
+      element = element.getParent();
+    }
+    return null;
+  }
+
+  @Nullable
+  String findMessageWithNullableParent(@NotNull Element element) {
+    while (element != null) {
+      if (element.getMessage() != null) {
+        return element.getMessage();
+      }
+      element = element.getNullableParent();
+    }
+    return null;
+  }
+
+}
+
+interface Element {
+  Element getParent();
+  @Nullable Element getNullableParent();
+  @Nullable String getMessage();
+}