Commits on Apr 26, 2016

1. shallow Clone for #[derive(Copy,Clone)] …

   Changes #[derive(Copy, Clone)] to use a faster impl of Clone when
   both derives are present, and there are no generics in the type.
   
   The faster impl is simply returning *self (which works because the
   type is also Copy). See the comments in libsyntax_ext/deriving/clone.rs
   for more details.
   
   There are a few types which are Copy but not Clone, in violation
   of the definition of Copy. These include large arrays and tuples. The
   very existence of these types is arguably a bug, but in order for this
   optimization not to change the applicability of #[derive(Copy, Clone)],
   the faster Clone impl also injects calls to a new function,
   core::clone::assert_receiver_is_clone, to verify that all members are
   actually Clone.
   
   This is not a breaking change, because pursuant to RFC 1521, any type
   that implements Copy should not do any observable work in its Clone
   impl.

   

   durka committed Apr 26, 2016
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