8067422: Lambda method names are unnecessarily unstable

Lambda method numbers are now assigned per class for non-serializable lambdas.

Reviewed-by: mcimadamore, rfield

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

@@ -1176,12 +1176,14 @@ public class LambdaToMethod extends TreeTranslator {
         @Override
         public void visitClassDef(JCClassDecl tree) {
             List<Frame> prevStack = frameStack;
+            int prevLambdaCount = lambdaCount;
             SyntheticMethodNameCounter prevSyntheticMethodNameCounts =
                     syntheticMethodNameCounts;
             Map<ClassSymbol, Symbol> prevClinits = clinits;
             DiagnosticSource prevSource = log.currentSource();
             try {
                 log.useSource(tree.sym.sourcefile);
+                lambdaCount = 0;
                 syntheticMethodNameCounts = new SyntheticMethodNameCounter();
                 prevClinits = new HashMap<>();
                 if (tree.sym.owner.kind == MTH) {
@@ -1208,6 +1210,7 @@ public class LambdaToMethod extends TreeTranslator {
             finally {
                 log.useSource(prevSource.getFile());
                 frameStack = prevStack;
+                lambdaCount = prevLambdaCount;
                 syntheticMethodNameCounts = prevSyntheticMethodNameCounts;
                 clinits = prevClinits;
             }

langtools/test/tools/javac/lambda/lambdaNaming/TestNonSerializableLambdaNameStability.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2014, 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.
+ *
+ * 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 8067422
+ * @summary Check that the lambda names are not unnecessarily unstable
+ * @library /tools/lib
+ * @build ToolBox
+ * @run main TestNonSerializableLambdaNameStability
+ */
+
+import com.sun.tools.classfile.ClassFile;
+import com.sun.tools.classfile.Method;
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.List;
+import javax.tools.StandardLocation;
+
+public class TestNonSerializableLambdaNameStability {
+
+    public static void main(String... args) throws Exception {
+        new TestNonSerializableLambdaNameStability().run();
+    }
+
+    String lambdaSource = "public class L%d {\n" +
+                          "    public static class A {\n" +
+                          "        private Runnable r = () -> { };\n" +
+                          "    }\n" +
+                          "    public static class B {\n" +
+                          "        private Runnable r = () -> { };\n" +
+                          "    }\n" +
+                          "    private Runnable r = () -> { };\n" +
+                          "}\n";
+
+    String expectedLambdaMethodName = "lambda$new$0";
+
+    void run() throws Exception {
+        List<String> sources = new ArrayList<>();
+
+        for (int i = 0; i < 3; i++) {
+            sources.add(String.format(lambdaSource, i));
+        }
+
+        ToolBox tb = new ToolBox();
+
+        try (ToolBox.MemoryFileManager fm = new ToolBox.MemoryFileManager()) {
+            tb.new JavacTask()
+              .sources(sources.toArray(new String[sources.size()]))
+              .fileManager(fm)
+              .run();
+
+            for (String file : fm.files.get(StandardLocation.CLASS_OUTPUT).keySet()) {
+                byte[] fileBytes = fm.getFileBytes(StandardLocation.CLASS_OUTPUT, file);
+                try (InputStream in = new ByteArrayInputStream(fileBytes)) {
+                    boolean foundLambdaMethod = false;
+                    ClassFile cf = ClassFile.read(in);
+                    StringBuilder seenMethods = new StringBuilder();
+                    String sep = "";
+                    for (Method m : cf.methods) {
+                        String methodName = m.getName(cf.constant_pool);
+                        if (expectedLambdaMethodName.equals(methodName)) {
+                            foundLambdaMethod = true;
+                            break;
+                        }
+                        seenMethods.append(sep);
+                        seenMethods.append(methodName);
+                        sep = ", ";
+                    }
+
+                    if (!foundLambdaMethod) {
+                        throw new AbstractMethodError("Did not find the lambda method, " +
+                                                      "found methods: " + seenMethods.toString());
+                    }
+                }
+            }
+        }
+    }
+}