Allow trailing commas in function parameter lists

test/mjsunit/arguments-extra-commas.js

 // Copyright 2016 the V8 project authors. All rights reserved.

[adamk, 2016/06/28 21:10:51]

For new files please use the shorter copyright notice (see most test files in
harmony/ for examples).

[adamk, 2016/06/28 21:10:52]

Also please put this file in mjsunit/harmony/ to reflect that it's for a
not-yet-launched feature.

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 // modification, are permitted provided that the following conditions are
 // met:
 //
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 //       notice, this list of conditions and the following disclaimer.
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 //       with the distribution.
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 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --allow-natives-syntax --turbo-escape
+// Flags: --harmony-trailing-commas-in-parameters
 
-function f() {
-  var x = new Array(2);
-  x[0] = 23.1234;
-  x[1] = 25.1234;
-  %DeoptimizeNow();
-  return x[0];
-}
 
-assertEquals(f(), 23.1234);
-assertEquals(f(), 23.1234);
-%OptimizeFunctionOnNextCall(f);
-assertEquals(f(), 23.1234);
+function f1(a)      { return arguments.length; }
+function f2(a,b)    { return arguments.length; }
+function f3(a,b,c)  { return arguments.length; }
+function g1(a,)     { return arguments.length; }
+function g2(a,b,)   { return arguments.length; }
+function g3(a,b,c,) { return arguments.length; }
+
+[f1, f2, f3].forEach(function(f) {

[adamk, 2016/06/28 21:10:51]

Sorry, I meant the "length" property on functions themselves, that is:

assertEquals(2, (function(a, b,){}).length)

+  assertEquals(0, f());
+
+  assertEquals(1, f(1));
+  assertEquals(2, f(1,2));
+  assertEquals(3, f(1,2,3));
+  assertEquals(4, f(1,2,3,4));
+  assertEquals(5, f(1,2,3,4,5));
+
+  assertEquals(1, f(1,));
+  assertEquals(2, f(1,2,));
+  assertEquals(3, f(1,2,3,));
+  assertEquals(4, f(1,2,3,4,));
+  assertEquals(5, f(1,2,3,4,5,));
+
+  assertEquals(0, f(...[]));
+  assertEquals(3, f(...[1, 2, 3]));
+  assertEquals(3, f(...[1,], 2, ...[3,]));
+
+  assertEquals(0, f(...[],));
+  assertEquals(3, f(...[1, 2, 3],));
+  assertEquals(3, f(...[1,], 2, ...[3,],));
+});