8012556: Implement lambda methods on interfaces as static

8006140: Javac NPE compiling Lambda expression on initialization expression of static field in interface

Lambdas occurring in static contexts or those not needing instance information should be generated into static methods.  This has long been the case for classes.  However, as a work-around to the lack of support for statics on interfaces, interface lambda methods have been generated into default methods.  For lambdas in interface static contexts (fields and static methods) this causes an NPE in javac because there is no 'this'.  MethodHandles now support static methods on interfaces.  This changeset allows lambda methods to be generated as static interface methods.  An existing bug in Hotspot (8013875) is exposed in a test when the "-esa" flag is used.  This test and another test that already exposed this bug have been marked with @ignore.

Reviewed-by: mcimadamore

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

@@ -1764,12 +1764,13 @@ public class LambdaToMethod extends TreeTranslator {
                 }
                 boolean inInterface = translatedSym.owner.isInterface();
                 boolean thisReferenced = !getSymbolMap(CAPTURED_THIS).isEmpty();
-                boolean needInstance = thisReferenced || inInterface;
 
-                // If instance access isn't needed, make it static
+                // If instance access isn't needed, make it static.
-                // Interface methods much be public default methods, otherwise make it private
+                // Interface instance methods must be default methods.
-                translatedSym.flags_field = SYNTHETIC | (needInstance? 0 : STATIC) |
+                // Awaiting VM channges, default methods are public
-                        (inInterface? PUBLIC | DEFAULT : PRIVATE);
+                translatedSym.flags_field = SYNTHETIC |
+                        ((inInterface && thisReferenced)? PUBLIC : PRIVATE) |
+                        (thisReferenced? (inInterface? DEFAULT : 0) : STATIC);
 
                 //compute synthetic params
                 ListBuffer<JCVariableDecl> params = ListBuffer.lb();

langtools/test/tools/javac/lambda/LambdaInterfaceStaticField.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8006140
+ * @summary Javac NPE compiling Lambda expression on initialization expression of static field in interface
+ * @compile LambdaInterfaceStaticField.java
+ */
+
+interface LambdaInterfaceStaticField {
+  interface I {
+     int m();
+  }
+  public static final I fld = () -> 5;
+}

langtools/test/tools/javac/lambda/MethodReference66.java

@@ -24,6 +24,7 @@
 /*
  * @test
  * @bug 8009299
+ * @ignore 8013875: Incorrect vtable index being set during methodHandle creation for static
  * @summary Javac crashes when compiling method reference to static interface method
  * @run main/othervm -Xverify:none MethodReference66
  */

langtools/test/tools/javac/lambda/bytecode/TestLambdaBytecode.java

@@ -306,7 +306,7 @@ public class TestLambdaBytecode
     String makeIndyType(int id) {
         StringBuilder buf = new StringBuilder();
         buf.append("(");
-        if (!mk2.isStatic() || mk1.inInterface()) {
+        if (!mk2.isStatic()) {
             buf.append(String.format("LTest%d;", id));
         }
         buf.append(")Ljava/lang/Runnable;");

langtools/test/tools/javac/lambda/lambdaExecution/InInterface.java

@@ -26,6 +26,7 @@
 /**
  * @test
  * @bug 8003639
+ * @ignore 8013875: Incorrect vtable index being set during methodHandle creation for static
  * @summary convert lambda testng tests to jtreg and add them
  * @run testng InInterface
  */