Implement the apply functionality for dart2js and currently just put it in a test.

tests/compiler/dart2js_native/apply_test.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+//
+// This test should move to a language test once the apply method
+// gets into the specification.
+
+apply(Function function, ArgumentDescriptor args) {
+  int nbArguments = 0;

[kasperl, 2012/09/26 13:23:43]

nbArguments -> argumentCount?

[ngeoffray, 2012/09/26 13:40:45]

Done.

+  StringBuffer buffer = new StringBuffer();
+  List arguments = [];
+
+  if (args.positionalArguments != null) {
+    nbArguments += args.positionalArguments.length;
+    arguments.addAll(args.positionalArguments);
+  }
+
+  // Sort the named arguments to get the right selector name and
+  // arguments order.

[kasperl, 2012/09/26 13:23:43]

Maybe add a comment that explains why you've decided on using JS sorting?

[ngeoffray, 2012/09/26 13:40:45]

Done.

+  if (args.namedArguments != null && !args.namedArguments.isEmpty()) {
+    List<String> namedArguments = args.namedArguments.getKeys();

[kasperl, 2012/09/26 13:23:43]

Are we assuming too much about what is returned from getKeys()? This code will
crash if it isn't a JS array, right?

[ngeoffray, 2012/09/26 13:40:45]

Yes, it will crash. I changed the code to do new List.from instead.

+    nbArguments += namedArguments.length;
+    JS('void', '#.sort()', namedArguments);
+    namedArguments.forEach((String name) {
+      buffer.add('\$$name');
+      arguments.add(args.namedArguments[name]);
+    });
+  }
+
+  String selectorName = 'call\$$nbArguments$buffer';
+  var jsFunction = JS('var', '#[#]', function, selectorName);
+  if (jsFunction == null) {
+    throw new NoSuchMethodError(function, selectorName, arguments);
+  }
+  return JS('var', '#.apply(#, #)', jsFunction, function, arguments);

[kasperl, 2012/09/26 13:23:43]

Add a comment that explains why you need 'this' to be bound to the function.

[ngeoffray, 2012/09/26 13:40:45]

Done.

+}
+
+class ArgumentDescriptor {
+  final List positionalArguments;
+  final Map<String, Dynamic> namedArguments;
+
+  ArgumentDescriptor(this.positionalArguments, this.namedArguments);
+}
+
+void throwsNSME(function) {
+  Expect.throws(function, (e) => e is NoSuchMethodError);
+}
+
+main() {
+  var c1 = () => 'c1';
+  var c2 = (a) => 'c2 $a';
+  var c3 = ([a = 1]) => 'c3 $a';
+  var c4 = ({a: 1}) => 'c4 $a';
+  var c5 = ({a: 1, b: 2}) => 'c5 $a $b';
+  var c6 = ({b: 1, a: 2}) => 'c6 $a $b';
+
+  // TODO(ngeoffray): Remove these calls. They are currently needed
+  // because otherwise we would not generate the stubs. Once apply is
+  // in the specification, we should change the compiler to emit stubs
+  // for closures once it sees an 'apply' selector.
+  c1();
+  c2(1);
+  c3(); c3(1);
+  c4(); c4(a: 1);
+  c5(); c5(a: 1); c5(b: 2); c5(a:1, b: 2);
+  c6(); c6(a: 1); c6(b: 2); c6(a:1, b: 2);
+
+  Expect.equals('c1', apply(c1, new ArgumentDescriptor(null, null)));
+  Expect.equals('c1', apply(c1, new ArgumentDescriptor([], null)));
+  Expect.equals('c1', apply(c1, new ArgumentDescriptor([], {})));
+  Expect.equals('c1', apply(c1, new ArgumentDescriptor(null, {})));
+  throwsNSME(() => apply(c1, new ArgumentDescriptor([1], null)));
+  throwsNSME(() => apply(c1, new ArgumentDescriptor([1], {'a': 2})));
+  throwsNSME(() => apply(c1, new ArgumentDescriptor(null, {'a': 2})));
+
+  Expect.equals('c2 1', apply(c2, new ArgumentDescriptor([1], null)));
+  Expect.equals('c2 1', apply(c2, new ArgumentDescriptor([1], {})));
+  throwsNSME(() => apply(c2, new ArgumentDescriptor(null, null)));
+  throwsNSME(() => apply(c2, new ArgumentDescriptor([], null)));
+  throwsNSME(() => apply(c2, new ArgumentDescriptor(null, {})));
+  throwsNSME(() => apply(c2, new ArgumentDescriptor(null, {'a': 1})));
+
+  Expect.equals('c3 1', apply(c3, new ArgumentDescriptor([], null)));
+  Expect.equals('c3 2', apply(c3, new ArgumentDescriptor([2], {})));
+  throwsNSME(() => apply(c3, new ArgumentDescriptor([1, 2], null)));
+  // TODO(ngeoffray): Should be throwsNSME with the new parameter
+  // specification.
+  Expect.equals('c3 1', apply(c3, new ArgumentDescriptor(null, {'a': 1})));
+
+  Expect.equals('c4 1', apply(c4, new ArgumentDescriptor([], null)));
+  Expect.equals('c4 2', apply(c4, new ArgumentDescriptor([], {'a': 2})));
+  Expect.equals('c4 1', apply(c4, new ArgumentDescriptor(null, null)));
+  Expect.equals('c4 1', apply(c4, new ArgumentDescriptor([], {})));
+  throwsNSME(() => apply(c4, new ArgumentDescriptor([1], {'a': 1})));
+  throwsNSME(() => apply(c4, new ArgumentDescriptor([1], {})));
+  throwsNSME(() => apply(c4, new ArgumentDescriptor([], {'a': 1, 'b': 2})));
+
+  Expect.equals('c5 1 2', apply(c5, new ArgumentDescriptor([], null)));
+  Expect.equals('c5 3 2', apply(c5, new ArgumentDescriptor([], {'a': 3})));
+  Expect.equals('c5 1 2', apply(c5, new ArgumentDescriptor(null, null)));
+  Expect.equals('c5 1 2', apply(c5, new ArgumentDescriptor([], {})));
+  Expect.equals('c5 3 4',
+      apply(c5, new ArgumentDescriptor([], {'a': 3, 'b': 4})));
+  Expect.equals('c5 4 3',
+      apply(c5, new ArgumentDescriptor([], {'b': 3, 'a': 4})));
+  Expect.equals('c5 1 3',
+      apply(c5, new ArgumentDescriptor([], {'b': 3})));
+  throwsNSME(() => apply(c5, new ArgumentDescriptor([1], {'a': 1})));
+  throwsNSME(() => apply(c5, new ArgumentDescriptor([1], {})));
+  throwsNSME(() =>
+      apply(c5, new ArgumentDescriptor([], {'a': 1, 'b': 2, 'c': 3})));
+
+  Expect.equals('c6 2 1', apply(c6, new ArgumentDescriptor([], null)));
+  Expect.equals('c6 3 1', apply(c6, new ArgumentDescriptor([], {'a': 3})));
+  Expect.equals('c6 2 1', apply(c6, new ArgumentDescriptor(null, null)));
+  Expect.equals('c6 2 1', apply(c6, new ArgumentDescriptor([], {})));
+  Expect.equals('c6 3 4',
+      apply(c6, new ArgumentDescriptor([], {'a': 3, 'b': 4})));
+  Expect.equals('c6 4 3',
+      apply(c6, new ArgumentDescriptor([], {'b': 3, 'a': 4})));
+  Expect.equals('c6 2 3',
+      apply(c6, new ArgumentDescriptor([], {'b': 3})));
+  throwsNSME(() => apply(c6, new ArgumentDescriptor([1], {'a': 1})));
+  throwsNSME(() => apply(c6, new ArgumentDescriptor([1], {})));
+  throwsNSME(() =>
+      apply(c6, new ArgumentDescriptor([], {'a': 1, 'b': 2, 'c': 3})));
+}