[es8] More spec compliant syntactic tail calls implementation.

test/mjsunit/es7/syntactic-tail-call.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --allow-natives-syntax --harmony-explicit-tailcalls
 
 Error.prepareStackTrace = (error,stack) => {
   error.strace = stack;
   return error.message + "\n    at " + stack.join("\n    at ");
 }
@@ skipping 205 matching lines @@
   test();
   test();
   %OptimizeFunctionOnNextCall(test);
   test();
 })();
 
 
 // Tail calling via various expressions.
 (function() {
   function g1(a) {
-    return continue f([f, g1, test], false) || f([f, test], true);
+    return f([f, g1, test], false) || continue f([f, test], true);
   }
 
   function g2(a) {
-    return continue f([f, g2, test], true) && f([f, test], true);
+    return f([f, g2, test], true) && continue f([f, test], true);
   }
 
   function g3(a) {
-    return continue f([f, g3, test], 13), f([f, test], 153);
+    return f([f, g3, test], 13), continue f([f, test], 153);
   }
 
   function test() {
     assertEquals(true, g1());
     assertEquals(true, g2());
     assertEquals(153, g3());
   }
   test();
   test();
   %OptimizeFunctionOnNextCall(test);
@@ skipping 152 matching lines @@
 (function () {
   function g1(a) {
     return continue (() => { return continue f_153([f_153, test]); })();
   }
 
   function g2(a) {
     return continue (() => continue f_153([f_153, test]))();
   }
 
   function g3(a) {
-    var closure = () => continue f([f, closure, test], true)
-                                            ? f_153([f_153, test])
-                                            : f_153([f_153, test]);
-
+    var closure = () => f([f, closure, test], true)
+                              ? continue f_153([f_153, test])
+                              : f_153([f_153, test]);

[rossberg, 2016/05/02 10:59:40]

Shouldn't you need a `continue` here, too, to be equivalent to the previous
version?

[Igor Sheludko, 2016/05/04 10:28:55]

The call f([f, closure, test], true) returns true.
Whatever... Done.

     return continue closure();
   }
 
   function test() {
     assertEquals(153, g1());
     assertEquals(153, g2());
     assertEquals(153, g3());
   }
   test();
   test();
   %OptimizeFunctionOnNextCall(test);
   test();
 })();