[java-dfa] Test for IDEA-375523 False positive "Argument might be null" with Guava Streams

GitOrigin-RevId: b6569cf1c45c5de3486d823f37a1426f81d0382d

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

@@ -0,0 +1,44 @@
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.NotNullByDefault;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.List;
+import java.util.stream.Stream;
+
+abstract class StreamsNull {
+  @NotNullByDefault
+  static class Streams {
+    @SafeVarargs
+    static native <T extends @Nullable Object> Stream<T> concat(Stream<? extends T>... streams);
+  }
+
+  List<String> calc(Stream<Leg> positions, Stream<Leg> leg1, Stream<Leg> leg2, double v) {
+    return Streams.concat(
+        positions.map(Leg::getInstrument),
+        leg1.map(Leg::getInstrument),
+        leg2.map(Leg::getInstrument)
+      )
+      .filter(i -> isInteresting(i, v))
+      .toList();
+  }
+
+  List<String> calc2(Stream<Leg> positions, Stream<Leg> leg1, Stream<Leg> leg2, double v) {
+    return Streams.concat(
+        positions.map(Leg::getInstrument),
+        leg1.map(Leg::getInstrument2),
+        leg2.map(Leg::getInstrument)
+      )
+      .filter(i -> isInteresting(<warning descr="Argument 'i' might be null">i</warning>, v))
+      .toList();
+  }
+
+  protected abstract boolean isInteresting(@NotNull String instrument,
+                                           double v);
+}
+
+interface Leg {
+  @NotNull
+  String getInstrument();
+  @Nullable
+  String getInstrument2();
+}