When += (and similar operations) are converted to = + ,

frog/gen.dart

Index: frog/gen.dart
===================================================================
--- frog/gen.dart	(revision 2468)
+++ frog/gen.dart	(working copy)
@@ -1870,9 +1870,17 @@
         return;
       }
       return x.invoke(this, name, node, new Arguments(null, [y]));
-    } else {
-      return _visitAssign(assignKind, node.x, node.y, node, null, isVoid);
-    }
+    } else if ((assignKind != 0) && (node.y is BinaryExpression)){
+      BinaryExpression y = node.y;
+      if (TokenKind.infixPrecedence(y.op.kind) <=
+          TokenKind.infixPrecedence(assignKind)) {

[jimhug, 2011/12/15 17:43:18]

I would prefer not to include this check.  My general rule is that if you need
to think about precedence very hard then it is better to include parens.  This
check is relying on js and dart precedences to be identical - which I would have
to verify before guaranteeing.  Does this change make a big difference to the
generated code?

[dgrove, 2011/12/15 17:51:45]

It doesn't any changes in minfrog, for instance. It could make some generated JS
a bit less readable, but that could be a reasonable price to pay.

I'm going to take this out, and we can always make this smarter if we need to.
On 2011/12/15 17:43:18, jimhug wrote:

[dgrove, 2011/12/15 17:51:45]

Done.

+        // This handles transforming A x= B y C => A = A x (B y C) when
+        // precedence of x >= precedence of y. 
+        return _visitAssign(assignKind, node.x,
+            new ParenExpression(node.y, node.y.span), node, null, isVoid);
+      } 
+    }  
+    return _visitAssign(assignKind, node.x, node.y, node, null, isVoid);
   }
 
   /**