Implement call operator.

tests/language/call_operator_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.
 
 
 // simple test with no types in signature
 class A1 {
-  operator call() => 42;
+  call() => 42;
 }
 
 // same test, include return type
 class A2 {
-  int operator call() => 35;
+  int call() => 35;
 }
 
 class B {
-  call() => 28; // expect warning, should use 'operator call'
+  call() => 28;
 }
 
 // A call() operator can have any arity
 class C {
-  operator call(arg) => 7 * arg;
+  call(arg) => 7 * arg;
 }
 
 // Test named arguments
 class D {
-  operator call([arg=6]) => 7 * arg;
+  call([arg=6]) => 7 * arg;
 }
 
-// non-trvial method body combination of positional and named
+// non-trivial method body combination of positional and named
 class E {
-  String operator call(String str, [int count=1]) {
+  String call(String str, [int count=1]) {
     String result = "";

[kasperl, 2012/08/10 10:16:28]

How about using a StringBuffer here? Seems cleaner.

[floitsch, 2012/08/10 12:19:16]

Done.

     for (var i = 0; i < count; i++) {
-      result += str;
+      result = "$result$str";
       if (i < count -1) {

[kasperl, 2012/08/10 10:16:28]

-1 => - 1

[floitsch, 2012/08/10 12:19:16]

Done.

-        result += ':';
+        result = '$result:';
       }
     }
     return result;
   }
 }
 
 main() {
   var a1 = new A1();
   Expect.equals(42, a1());
   Expect.equals(42, a1.call());
@@ skipping 19 matching lines @@
   Expect.equals(14, d.call(arg:2));
 
   var e = new E();
   Expect.equals("foo", e("foo"));
   Expect.equals("foo:foo", e("foo", 2));
   Expect.equals("foo:foo:foo", e("foo", count:3));
   Expect.equals("foo", e.call("foo"));
   Expect.equals("foo:foo", e.call("foo", 2));
   Expect.equals("foo:foo:foo", e.call("foo", count:3));
 }