Implement a destination propagation pass

Author: jonas-schievink

src/librustc_mir/dataflow/impls/mod.rs

@@ -192,7 +192,7 @@ impl<'a, 'tcx> HasMoveData<'tcx> for DefinitelyInitializedPlaces<'a, 'tcx> {
 
 /// `EverInitializedPlaces` tracks all places that might have ever been
 /// initialized upon reaching a particular point in the control flow
-/// for a function, without an intervening `Storage Dead`.
+/// for a function, without an intervening `StorageDead`.
 ///
 /// This dataflow is used to determine if an immutable local variable may
 /// be assigned to.

src/librustc_mir/lib.rs

@@ -6,6 +6,7 @@ Rust MIR: a lowered representation of Rust.
 
 #![feature(nll)]
 #![feature(in_band_lifetimes)]
+#![feature(bindings_after_at)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]