Skip access method when lambda body method can be promoted.

Author: JakeWharton

end-to-end-tests/src/test/java/net/orfjackal/retrolambda/test/LambdaClassesTest.java

@@ -4,6 +4,7 @@
 
 package net.orfjackal.retrolambda.test;
 
+import com.google.common.collect.ImmutableSet;
 import org.junit.Test;
 
 import java.lang.reflect.Method;
@@ -85,4 +86,24 @@ private NonCapturing() {
             };
         }
     }
+
+
+    @Test
+    public void lambda_bodies_contain_no_unnecessary_methods() throws ClassNotFoundException {
+        Set<String> expected = ImmutableSet.of("lambda$main$0", "main");
+
+        Set<String> actual = new HashSet<>();
+        for (Method method : HasLambdaBody.class.getDeclaredMethods()) {
+            actual.add(method.getName());
+        }
+        assertThat(actual, is(expected));
+    }
+
+    @SuppressWarnings("UnusedDeclaration")
+    private class HasLambdaBody {
+        private void main() {
+            Runnable lambda = () -> {
+            };
+        }
+    }
 }

retrolambda/src/main/java/net/orfjackal/retrolambda/interfaces/RemoveDefaultMethodBodies.java

@@ -4,6 +4,7 @@
 
 package net.orfjackal.retrolambda.interfaces;
 
+import net.orfjackal.retrolambda.lambdas.LambdaNaming;
 import org.objectweb.asm.*;
 import org.objectweb.asm.tree.MethodNode;
 
@@ -18,7 +19,8 @@ public RemoveDefaultMethodBodies(ClassVisitor next) {
 
     @Override
     public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
-        if (isPrivateInstanceMethod(access)) { // lambda impl methods which capture `this` are private instance methods
+        if (LambdaNaming.isBodyMethod(access, name)) {
+            // lambda impl methods which capture `this` are synthetic instance methods
             return null;
         }
         if (isDefaultMethod(access)) {
@@ -29,10 +31,6 @@ public MethodVisitor visitMethod(int access, String name, String desc, String si
         }
     }
 
-    private static boolean isPrivateInstanceMethod(int access) {
-        return isPrivateMethod(access) && isInstanceMethod(access);
-    }
-
     private static boolean isDefaultMethod(int access) {
         return isConcreteMethod(access) && isInstanceMethod(access);
     }

retrolambda/src/main/java/net/orfjackal/retrolambda/lambdas/BackportLambdaInvocations.java

@@ -48,6 +48,10 @@ private static void resetLambdaClassSequenceNumber() {
 
     @Override
     public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
+        if (LambdaNaming.isBodyMethod(access, name)) {
+            // Ensure our generated lambda class is able to call this method.
+            access &= ~ACC_PRIVATE;
+        }
         if (LambdaNaming.isDeserializationHook(access, name, desc)) {
             return null; // remove serialization hooks; we serialize lambda instances as-is
         }
@@ -62,6 +66,13 @@ Handle getLambdaAccessMethod(Handle implMethod) {
             // the method will be relocated to a companion class
             return implMethod;
         }
+        if (LambdaNaming.isBodyMethodName(implMethod.getName())) {
+            if (implMethod.getTag() == H_INVOKESPECIAL) {
+                // The private body method is now package so switch its invocation from special to virtual.
+                return new Handle(H_INVOKEVIRTUAL, implMethod.getOwner(), implMethod.getName(), implMethod.getDesc());
+            }
+            return implMethod;
+        }
         // TODO: do not generate an access method if the impl method is not private (probably not implementable with a single pass)
         String name = "access$lambda$" + lambdaAccessToImplMethods.size();
         String desc = getLambdaAccessMethodDesc(implMethod);

retrolambda/src/main/java/net/orfjackal/retrolambda/lambdas/LambdaNaming.java

@@ -37,4 +37,12 @@ public static boolean isPlatformFactoryMethod(int access, String name, String de
                 && desc.equals(targetDesc)
                 && Flags.hasFlag(access, ACC_PRIVATE | ACC_STATIC);
     }
+
+    public static boolean isBodyMethodName(String name) {
+        return name.startsWith("lambda$");
+    }
+
+    public static boolean isBodyMethod(int access, String name) {
+        return isBodyMethodName(name) && Flags.hasFlag(access, ACC_SYNTHETIC);
+    }
 }