Guard the use of write in the implementation of print.

lib/compiler/implementation/lib/js_helper.dart

Index: lib/compiler/implementation/lib/js_helper.dart
diff --git a/lib/compiler/implementation/lib/js_helper.dart b/lib/compiler/implementation/lib/js_helper.dart
index 1027a46bae0699588e200b47cc0e574c0affbd01..d2a5c030948b79526dce820b62d65c504563828b 100644
--- a/lib/compiler/implementation/lib/js_helper.dart
+++ b/lib/compiler/implementation/lib/js_helper.dart
@@ -370,17 +370,22 @@ class Primitives {
    * by defining a function in JavaScript called "dartPrint".
    */
   static void printString(String string) {
-    var hasDartPrint = JS('bool', @'typeof dartPrint == "function"');
+    bool hasDartPrint = JS('bool', @'typeof dartPrint == "function"');

[Emily Fortuna, 2012/07/05 11:46:42]

nit: the style guide suggests having leaving variables untyped if they're local
and it's obvious, but if you prefer it this way, I can accept that too.

[kasperl, 2012/07/05 11:49:03]

Done.

     if (hasDartPrint) {
       JS('void', @'dartPrint(#)', string);
-    } else {
-      var hasConsole = JS('bool', @'typeof console == "object"');
-      if (hasConsole) {
-        JS('void', @'console.log(#)', string);
-      } else {
-        JS('void', @'write(#)', string);
-        JS('void', @'write("\n")');
-      }
+      return;
+    }
+
+    bool hasConsole = JS('bool', @'typeof console == "object"');

[Emily Fortuna, 2012/07/05 11:46:42]

nit: personally I'd write this as 
if (hasDartPrint) {
       JS('void', @'dartPrint(#)', string);
} else if(JS('bool', @'typeof console == "object"')) {
      JS('void', @'console.log(#)', string);
} else if (JS('bool', @'typeof write == "function"')) {
etc

just to make the control flow a little clearer, but this is fine, too if you
prefer.

[kasperl, 2012/07/05 11:49:03]

In this case, I think the JS expressions are a bit obscure so I prefer to be
able to "name" them. With the extra local variables the nesting gets a bit
annoying which is why I went for the variant with explicit returns.

+    if (hasConsole) {
+      JS('void', @'console.log(#)', string);
+      return;
+    }
+
+    bool hasWrite = JS('bool', @'typeof write == "function"');
+    if (hasWrite) {
+      JS('void', @'write(#)', string);
+      JS('void', @'write("\n")');
     }
   }