add comment and move test

Author: msridhar

nullaway/src/main/java/com/uber/nullaway/generics/TypeSubstitutionUtils.java

@@ -292,10 +292,12 @@ public Type visitMethodType(Type.MethodType t, Type other) {
 
     @Override
     public Type visitClassType(Type.ClassType t, Type other) {
-      // Unwrap wildcard upper bounds
       if (other instanceof Type.WildcardType wt) {
         if (wt.isExtendsBound()) {
-          return visit(t, wt.type);
+          // As a temporary measure, we restore nullability annotations from the upper bound of the
+          // wildcard.
+          // TODO revisit this decision when we add fuller support for inference and wildcards.
+          return visit(t, wt.getExtendsBound());
         }
       }
 

nullaway/src/test/java/com/uber/nullaway/jspecify/GenericMethodLambdaOrMethodRefArgTests.java

@@ -413,6 +413,28 @@ void test() {
         .doTest();
   }
 
+  @Test
+  public void genericMethodLambdaArgWildCard() {
+    makeHelperWithInferenceFailureWarning()
+        .addSourceLines(
+            "Test.java",
+            """
+            import org.jspecify.annotations.*;
+            import java.util.function.Function;
+            @NullMarked
+            class Test {
+                static <T, R> R invokeWithReturn(Function <? super T, ? extends @Nullable R> mapper) {
+                    throw new RuntimeException();
+                }
+                static void test() {
+                    // legal, should infer R -> Object but then the type of the lambda as
+                    //  Function<Object, @Nullable Object> via wildcard upper bound
+                    Object x = invokeWithReturn(t -> null);
+                }
+            }""")
+        .doTest();
+  }
+
   private CompilationTestHelper makeHelperWithInferenceFailureWarning() {
     return makeTestHelperWithArgs(
         JSpecifyJavacConfig.withJSpecifyModeArgs(

nullaway/src/test/java/com/uber/nullaway/jspecify/GenericMethodTests.java

@@ -1042,28 +1042,6 @@ static class Foo<T extends @Nullable Object> {}
         .doTest();
   }
 
-  @Test
-  public void genericMethodLambdaArgWildCard() {
-    makeHelperWithInferenceFailureWarning()
-        .addSourceLines(
-            "Test.java",
-            """
-            import org.jspecify.annotations.*;
-            import java.util.function.Function;
-            @NullMarked
-            class Test {
-                static <T, R> R invokeWithReturn(Function <? super T, ? extends @Nullable R> mapper) {
-                    throw new RuntimeException();
-                }
-                static void test() {
-                    // legal, should infer R -> Object but then the type of the lambda as
-                    //  Function<Object, @Nullable Object> via wildcard upper bound
-                    Object x = invokeWithReturn(t -> null);
-                }
-            }""")
-        .doTest();
-  }
-
   @Test
   public void inferenceWithFieldAssignment() {
     makeHelper()