From a7bb7d320cf774a9ec6beb9e6b79b9bef30accf1 Mon Sep 17 00:00:00 2001
From: Manu Sridharan <msridhar@gmail.com>
Date: Fri, 23 Feb 2024 10:56:47 -0800
Subject: [PATCH] Check dereference of qualifier expression in method reference
 (#920)

Fixes #919
---
 .../main/java/com/uber/nullaway/NullAway.java    |  8 ++++++++
 .../com/uber/nullaway/NullAwayJava8Tests.java    | 16 ++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/nullaway/src/main/java/com/uber/nullaway/NullAway.java b/nullaway/src/main/java/com/uber/nullaway/NullAway.java
index 811ea592ed..1f67a4a0c0 100644
--- a/nullaway/src/main/java/com/uber/nullaway/NullAway.java
+++ b/nullaway/src/main/java/com/uber/nullaway/NullAway.java
@@ -986,6 +986,14 @@ public Description matchMemberReference(MemberReferenceTree tree, VisitorState s
     if (!withinAnnotatedCode(state)) {
       return Description.NO_MATCH;
     }
+    // Technically the qualifier expression of a method reference gets passed to
+    // Objects.requireNonNull, but it's fine to treat it as a dereference for error-checking
+    // purposes.  The error message will be slightly inaccurate
+    Description derefErrorDescription =
+        matchDereference(tree.getQualifierExpression(), tree, state);
+    if (derefErrorDescription != Description.NO_MATCH) {
+      state.reportMatch(derefErrorDescription);
+    }
     Symbol.MethodSymbol referencedMethod = ASTHelpers.getSymbol(tree);
     Symbol.MethodSymbol funcInterfaceSymbol =
         NullabilityUtil.getFunctionalInterfaceMethod(tree, state.getTypes());
diff --git a/nullaway/src/test/java/com/uber/nullaway/NullAwayJava8Tests.java b/nullaway/src/test/java/com/uber/nullaway/NullAwayJava8Tests.java
index 4ed038f916..6c37861534 100644
--- a/nullaway/src/test/java/com/uber/nullaway/NullAwayJava8Tests.java
+++ b/nullaway/src/test/java/com/uber/nullaway/NullAwayJava8Tests.java
@@ -22,4 +22,20 @@ public void functionalMethodSuperInterface() {
   public void functionalMethodOverrideSuperInterface() {
     defaultCompilationHelper.addSourceFile("NullAwayOverrideFunctionalInterfaces.java").doTest();
   }
+
+  @Test
+  public void methodReferenceOnNullableVariable() {
+    defaultCompilationHelper
+        .addSourceLines(
+            "Test.java",
+            "package com.uber;",
+            "import org.jspecify.annotations.Nullable;",
+            "class Test {",
+            "  public static boolean test(@Nullable String text, java.util.Set<String> s) {",
+            "    // BUG: Diagnostic contains: dereferenced expression text is @Nullable",
+            "    return s.stream().anyMatch(text::contains);",
+            "  }",
+            "}")
+        .doTest();
+  }
 }