3ddfb72512
For #7083. The metadata issue with the old version is now fixed. Ready for review. This is also not the full solution to #7083, because this is not supported yet: ``` trait Foo : Send { } impl <T: Send> Foo for T { } fn foo<T: Foo>(val: T, chan: std::comm::Chan<T>) { chan.send(val); } ``` cc @nikomatsakis