[java-psi] IDEA-379789 Guava. Possible NPE is not highlighted

Correct nullability when inferring type variable from eq and lower bounds

GitOrigin-RevId: 3c41bda2c36fd24568710ef2c9ca8b5ba0c70414

java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceSession.java

@@ -1192,6 +1192,9 @@ public class InferenceSession {
         return PsiTypes.nullType();
       } else {
         type = eqBound;
+        if (!lowerBound.equals(PsiTypes.nullType())) {
+          type = type.withNullability(eqBound.getNullability().join(lowerBound.getNullability()));
+        }
 
         if (isLowerBoundNotAssignable(var, eqBound, false)) {
           setErased();

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

@@ -0,0 +1,37 @@
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.NotNullByDefault;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.List;
+
+class MyTest {
+  @NotNullByDefault
+  static class Iterables {
+    public static native <T extends @Nullable Object> Iterable<T> concat(Iterable<? extends T> a, Iterable<? extends T> b);
+
+    public static native <T extends @Nullable Object> T[] toArray(
+      Iterable<? extends T> iterable, Class<@NotNull T> type);
+
+    public static native <T extends @Nullable Object> T get(
+      Iterable<T> iterable, int position);
+  }
+
+
+  void toArray(List<@Nullable String> l1) {
+    for (String s : Iterables.toArray(l1, String.class)) {
+      System.out.println(s.<warning descr="Method invocation 'length' may produce 'NullPointerException'">length</warning>());
+
+    }
+  }
+
+  void get(List<@Nullable String> l1) {
+    System.out.println(Iterables.get(l1, 0).<warning descr="Method invocation 'length' may produce 'NullPointerException'">length</warning>());
+
+  }
+
+  void foo(List<String> l1, List<String> l2) {
+    for (String s : Iterables.concat(l1, l2)) {
+      System.out.println(s.length());
+    }
+  }
+}

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

@@ -1,17 +0,0 @@
-import org.jetbrains.annotations.NotNullByDefault;
-import org.jetbrains.annotations.Nullable;
-
-import java.util.List;
-
-class MyTest {
-  @NotNullByDefault
-  static class Iterables {
-    public static native <T extends @Nullable Object> Iterable<T> concat(Iterable<? extends T> a, Iterable<? extends T> b);
-  }
-
-  void foo(List<String> l1, List<String> l2) {
-    for (String s : Iterables.concat(l1, l2)) {
-      System.out.println(s.length());
-    }
-  }
-}

java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection21Test.java

@@ -212,7 +212,7 @@ public class DataFlowInspection21Test extends DataFlowInspectionTestCase {
     doTest();
   }
   
-  public void testInheritNullableInstantiateUnknown() {
+  public void testGuavaIterablesProblems() {
     doTest();
   }