From b44761dc38b90efc5abd047d16a49b21b4864ca2 Mon Sep 17 00:00:00 2001
From: Tagir Valeev <tagir.valeev@jetbrains.com>
Date: Thu, 25 Sep 2025 17:36:21 +0200
Subject: [PATCH] [java-psi] IDEA-379789 Guava. Possible NPE is not highlighted

Correct nullability when inferring type variable from eq and lower bounds

GitOrigin-RevId: 3c41bda2c36fd24568710ef2c9ca8b5ba0c70414
---
 .../graphInference/InferenceSession.java      |  3 ++
 .../fixture/GuavaIterablesProblems.java       | 37 +++++++++++++++++++
 .../InheritNullableInstantiateUnknown.java    | 17 ---------
 .../DataFlowInspection21Test.java             |  2 +-
 4 files changed, 41 insertions(+), 18 deletions(-)
 create mode 100644 java/java-tests/testData/inspection/dataFlow/fixture/GuavaIterablesProblems.java
 delete mode 100644 java/java-tests/testData/inspection/dataFlow/fixture/InheritNullableInstantiateUnknown.java

diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceSession.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceSession.java
index dc6386ea9616..24e616ef6ed1 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceSession.java
+++ b/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();
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/GuavaIterablesProblems.java b/java/java-tests/testData/inspection/dataFlow/fixture/GuavaIterablesProblems.java
new file mode 100644
index 000000000000..d7e4c833e8f4
--- /dev/null
+++ b/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());
+    }
+  }
+}
\ No newline at end of file
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/InheritNullableInstantiateUnknown.java b/java/java-tests/testData/inspection/dataFlow/fixture/InheritNullableInstantiateUnknown.java
deleted file mode 100644
index b561fe7b085d..000000000000
--- a/java/java-tests/testData/inspection/dataFlow/fixture/InheritNullableInstantiateUnknown.java
+++ /dev/null
@@ -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());
-    }
-  }
-}
\ No newline at end of file
diff --git a/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection21Test.java b/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection21Test.java
index 5e96dceb6f13..e65611bfa14a 100644
--- a/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection21Test.java
+++ b/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();
   }