Only generate assert in checked mode.

lib/compiler/implementation/resolver.dart

Index: lib/compiler/implementation/resolver.dart
===================================================================
--- lib/compiler/implementation/resolver.dart	(revision 8394)
+++ lib/compiler/implementation/resolver.dart	(working copy)
@@ -1052,6 +1052,11 @@
       AbstractFieldElement field = target;
       target = field.getter;
     }
+    if (target == compiler.assertMethod && !node.isCall) {

[kasperl, 2012/06/08 05:34:05]

===

[ngeoffray, 2012/06/08 09:40:58]

Done.

+      // We can only use assert by calling it.
+      if (!inInstanceContext) error(node, MessageKind.CANNOT_RESOLVE, [node]);

[ahe, 2012/06/08 07:59:14]

I'm not sure about this error message.

I think it is more likely that the user is using assert incorrectly, so saying
something like "missing arguments to assert".

[ngeoffray, 2012/06/08 09:40:58]

Done.

+      target = null;
+    }
     // TODO(ngeoffray): Warn if target is null and the send is
     // unqualified.
     useElement(node, target);