getContainingMethod returns null for lambdas; fixes issue #3850

typetools · Nov 5, 2020 · 2aebf2e · 2aebf2e
1 parent 1791802
commit 2aebf2e
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Showing 2 changed files with 21 additions and 4 deletions.
diff --git a/checker/src/main/java/org/checkerframework/checker/nullness/NullnessTransfer.java b/checker/src/main/java/org/checkerframework/checker/nullness/NullnessTransfer.java
@@ -2,6 +2,7 @@
 
 import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.MethodInvocationTree;
+import com.sun.source.tree.MethodTree;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -202,17 +203,18 @@ protected TransferResult<NullnessValue, NullnessStore> strengthenAnnotationOfEqu
             if (nullnessTypeFactory.containsSameByClass(secondAnnos, PolyNull.class)) {
                 thenStore = thenStore == null ? res.getThenStore() : thenStore;
                 elseStore = elseStore == null ? res.getElseStore() : elseStore;
+                // TODO: methodTree is null for lambdas.  Handle that case.  See Issue3850.java.
+                MethodTree methodTree = analysis.getContainingMethod(secondNode.getTree());
                 ExecutableElement methodElem =
-                        TreeUtils.elementFromDeclaration(
-                                analysis.getContainingMethod(secondNode.getTree()));
+                        methodTree == null ? null : TreeUtils.elementFromDeclaration(methodTree);
                 if (notEqualTo) {
                     elseStore.setPolyNullNull(true);
-                    if (polyNullIsNonNull(methodElem, thenStore)) {
+                    if (methodElem != null && polyNullIsNonNull(methodElem, thenStore)) {
                         thenStore.setPolyNullNonNull(true);
                     }
                 } else {
                     thenStore.setPolyNullNull(true);
-                    if (polyNullIsNonNull(methodElem, elseStore)) {
+                    if (methodElem != null && polyNullIsNonNull(methodElem, elseStore)) {
                         elseStore.setPolyNullNonNull(true);
                     }
                 }

diff --git a/checker/tests/nullness/Issue3850.java b/checker/tests/nullness/Issue3850.java
@@ -0,0 +1,15 @@
+import org.checkerframework.checker.nullness.qual.PolyNull;
+
+class Issue3850 {
+
+    private static Iterable<@PolyNull String> toPos(Iterable<? extends @PolyNull Object> nodes) {
+        // :: error: (return.type.incompatible)
+        return transform(nodes, node -> node == null ? null : node.toString());
+    }
+
+    public static <F, T> Iterable<T> transform(
+            Iterable<? extends F> iterable,
+            java.util.function.Function<? super F, ? extends T> function) {
+        throw new Error("implementation is irrelevant");
+    }
+}