Allow trailing commas in function parameter lists

test/mjsunit/arguments-extra-commas.js

Index: test/mjsunit/arguments-extra-commas.js
diff --git a/test/mjsunit/compiler/escape-analysis-deopt-5.js b/test/mjsunit/arguments-extra-commas.js
similarity index 63%
copy from test/mjsunit/compiler/escape-analysis-deopt-5.js
copy to test/mjsunit/arguments-extra-commas.js
index e70f0b1221bd9ab9b33c72da70db4a38897fe34b..a1c5f3a41e0dbde318cc8ba4ee73ac51a974c3b3 100644
--- a/test/mjsunit/compiler/escape-analysis-deopt-5.js
+++ b/test/mjsunit/arguments-extra-commas.js
@@ -25,17 +25,36 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --allow-natives-syntax --turbo-escape
-
-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);
+// Flags: --harmony-trailing-commas-in-parameters
+
+
+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,],));
+});