Commits on Sep 10, 2019

1. lowering: extend temporary lifetimes around await …

   This commit changes the HIR lowering around `await` so that temporary
   lifetimes are extended. Previously, await was lowered as:
   
   ```rust
   {
       let mut pinned = future;
       loop {
           match ::std::future::poll_with_tls_context(unsafe {
               <::std::pin::Pin>::new_unchecked(&mut pinned)
           }) {
               ::std::task::Poll::Ready(result) => break result,
               ::std::task::Poll::Pending => {}
           }
           yield ();
       }
   }
   ```
   
   With this commit, await is lowered as:
   
   ```rust
   match future {
       mut pinned => loop {
           match ::std::future::poll_with_tls_context(unsafe {
               <::std::pin::Pin>::new_unchecked(&mut pinned)
           }) {
               ::std::task::Poll::Ready(result) => break result,
               ::std::task::Poll::Pending => {}
           }
           yield ();
       }
   }
   ```
   
   However, this change has the following side-effects:
   
   - All temporaries in future will be considered to live across a
     yield for the purpose of auto-traits.
   - Borrowed temporaries in future are likely to be considered to be live
     across the yield for the purpose of the generator transform.
   
   Signed-off-by: David Wood <david@davidtw.co>

   

   davidtwco committed Sep 10, 2019
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