8242214: NullPointerException in JDK 14 javac compiling a method reference

Ensuring a proper receiver is used to invoke protected method when method reference is unrolled into a lambda.

Reviewed-by: vromero

Author: lahodaj

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/LambdaToMethod.java

@@ -999,7 +999,10 @@ JCExpression getReceiverExpression() {
         private JCExpression makeReceiver(VarSymbol rcvr) {
             if (rcvr == null) return null;
             JCExpression rcvrExpr = make.Ident(rcvr);
-            Type rcvrType = tree.ownerAccessible ? tree.sym.enclClass().type : tree.expr.type;
+            boolean protAccess =
+                    isProtectedInSuperClassOfEnclosingClassInOtherPackage(tree.sym, owner);
+            Type rcvrType = tree.ownerAccessible && !protAccess ? tree.sym.enclClass().type
+                                                                : tree.expr.type;
             if (rcvrType == syms.arrayClass.type) {
                 // Map the receiver type to the actually type, not just "array"
                 rcvrType = tree.getQualifierExpression().type;
@@ -2270,11 +2273,6 @@ boolean isPrivateInOtherClass() {
                               types.erasure(owner.enclClass().asType()));
             }
 
-            boolean isProtectedInSuperClassOfEnclosingClassInOtherPackage() {
-                return ((tree.sym.flags() & PROTECTED) != 0 &&
-                        tree.sym.packge() != owner.packge());
-            }
-
             /**
              * Erasure destroys the implementation parameter subtype
              * relationship for intersection types.
@@ -2311,7 +2309,7 @@ final boolean needsConversionToLambda() {
                         needsVarArgsConversion() ||
                         isArrayOp() ||
                         (!nestmateLambdas && isPrivateInOtherClass()) ||
-                        isProtectedInSuperClassOfEnclosingClassInOtherPackage() ||
+                        isProtectedInSuperClassOfEnclosingClassInOtherPackage(tree.sym, owner) ||
                         !receiverAccessible() ||
                         (tree.getMode() == ReferenceMode.NEW &&
                           tree.kind != ReferenceKind.ARRAY_CTOR &&
@@ -2386,6 +2384,12 @@ private String classSig(Type type) {
         }
     }
 
+    private boolean isProtectedInSuperClassOfEnclosingClassInOtherPackage(Symbol targetReference,
+                                                                          Symbol currentClass) {
+        return ((targetReference.flags() & PROTECTED) != 0 &&
+                targetReference.packge() != currentClass.packge());
+    }
+
     /**
      * Signature Generation
      */

test/langtools/tools/javac/lambda/methodReference/ProtectedInaccessibleMethodRefTest2.java

@@ -23,45 +23,58 @@
 
 /*
  * @test
- * @bug 8234729
+ * @bug 8234729 8242214
  * @summary Javac should eagerly change code generation for method references to avert IllegalAccessError in future.
+ * @compile ProtectedInaccessibleMethodRefTest2.java
  * @run main ProtectedInaccessibleMethodRefTest2
  */
 
 import pack.I;
 import pack.J;
 
+import java.lang.reflect.Method;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.function.Function;
-import java.lang.reflect.Method;
-import java.util.concurrent.Callable;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.function.BiFunction;
 
 public final class ProtectedInaccessibleMethodRefTest2 extends I {
 
     public static void main(String... args) {
         ProtectedInaccessibleMethodRefTest2 m = new ProtectedInaccessibleMethodRefTest2();
         m.test(Paths.get("test"));
-        // Verify that the method reference has been folded into a lambda.
-        boolean lambdaFound = false;
+        // Verify that the method references have been folded into lambdas:
+        Set<String> methodNames = new HashSet<>();
         for (Method meth : ProtectedInaccessibleMethodRefTest2.class.getDeclaredMethods()) {
-            if (meth.getName().equals("lambda$test$0")) {
-                lambdaFound = true;
-                break;
-            }
+            methodNames.add(meth.getName());
         }
-        if (!lambdaFound) {
+        List<String> expectedMethods =
+                Arrays.asList("lambda$test$0", "lambda$test$1", "lambda$test$2");
+        if (!methodNames.containsAll(expectedMethods)) {
             throw new AssertionError("Did not find evidence of new code generation");
         }
     }
 
     void test(Path outputDir) {
-        Sub c = new Sub(this::readFile);
-        c.check(outputDir);
+        Sub c1 = new Sub(this::readFile);
+        c1.check(outputDir);
+        Sub c2 = new Sub(ProtectedInaccessibleMethodRefTest2::readFile, this);
+        c2.check(outputDir);
+        Sub c3 = new Sub(ProtectedInaccessibleMethodRefTest2::readFile2);
+        c3.check(outputDir);
     }
+
     public class Sub extends J {
         Sub(Function<Path,String> fileReader) {
             super(fileReader);
         }
+        Sub(BiFunction<ProtectedInaccessibleMethodRefTest2, Path,String> fileReader,
+            ProtectedInaccessibleMethodRefTest2 instance) {
+            super(p -> fileReader.apply(instance, p));
+        }
     }
 }

test/langtools/tools/javac/lambda/methodReference/pack/I.java

@@ -29,4 +29,8 @@ public class I {
     protected String readFile(Path file) {
         return file.toString();
     }
+
+    protected static String readFile2(Path file) {
+        return file.toString();
+    }
 }