Fix wrong assumptions I had on the isolate library.

frog/leg/ssa/builder.dart

Index: frog/leg/ssa/builder.dart
===================================================================
--- frog/leg/ssa/builder.dart	(revision 5514)
+++ frog/leg/ssa/builder.dart	(working copy)
@@ -1724,7 +1724,7 @@
         addGenericSendArgumentsToList(node.arguments, inputs);
         String name = compiler.namer.instanceMethodName(
             Namer.OPERATOR_EQUALS, 1);
-        push(new HForeign(new DartString.literal('#.$name'),
+        push(new HForeign(new DartString.literal('!!#.$name'),

[ngeoffray, 2012/03/15 12:15:39]

In case we don't propagate types, the check will return false, ie the previous
code will generate:

if (a.operator$eq$1 === true) { ... }

Which is obviously wrong because a.operator$eq$1 is either undefined or a
function.

                           const LiteralDartString('bool'),
                           inputs));
         break;