fix npe

Author: msridhar

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

@@ -948,7 +948,7 @@ private void handleMethodRefInGenericMethodInference(
     if (!referencedMethod.isStatic()) {
       // get the referenced method type as a member of the type of the qualifier expression
       qualifierType = getTreeType(memberReferenceTree.getQualifierExpression(), state);
-      if (qualifierType != null && !qualifierType.isRaw()) {
+      if (qualifierType != null) {
         referencedMethodType =
             TypeSubstitutionUtils.memberType(types, qualifierType, referencedMethod, config)
                 .asMethodType();
@@ -996,8 +996,10 @@ private void handleMethodRefInGenericMethodInference(
           !fiParamTypes.isEmpty(),
           "Expected receiver parameter for unbound method ref %s",
           memberReferenceTree);
-      Type receiverType = fiParamTypes.get(0);
-      solver.addSubtypeConstraint(receiverType, castToNonNull(qualifierType), false);
+      if (qualifierType != null) {
+        Type receiverType = fiParamTypes.get(0);
+        solver.addSubtypeConstraint(receiverType, qualifierType, false);
+      }
       fiStartIndex = 1;
     }
     if (fiParamTypes.size() - fiStartIndex != referencedParamTypes.size()) {

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

@@ -573,6 +573,30 @@ void testConsumeExplicitTypeArgs(Box<Integer> box, String sNonNull, @Nullable St
         .doTest();
   }
 
+  @Test
+  public void mapStream() {
+    makeHelperWithInferenceFailureWarning()
+        .addSourceLines(
+            "Test.java",
+            """
+            import org.jspecify.annotations.NullMarked;
+            import org.jspecify.annotations.Nullable;
+            import java.util.Map;
+            import java.util.stream.Collectors;
+            @NullMarked
+            class Test {
+              static Map<String,String> test(Map<String,String> map) {
+                return map.entrySet().stream()
+                    .collect(
+                        Collectors.toMap(
+                            Map.Entry::getKey,
+                            Map.Entry::getValue));
+              }
+            }
+            """)
+        .doTest();
+  }
+
   private CompilationTestHelper makeHelperWithInferenceFailureWarning() {
     return makeTestHelperWithArgs(
         JSpecifyJavacConfig.withJSpecifyModeArgs(