Remove IsPrefixOf impl for Place and use the NeoPlace one

Author: spastorino

src/librustc_mir/borrow_check/error_reporting.rs

@@ -698,7 +698,9 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
             // we're not in the uninteresting case where `B` is a
             // prefix of `D`), then report this as a more interesting
             // destructor conflict.
-            if !borrow.borrowed_place.is_prefix_of(place_span.0) {
+            let borrowed_neo_place = self.infcx.tcx.as_new_place(&borrow.borrowed_place);
+            let other_neo_place = self.infcx.tcx.as_new_place(place_span.0);
+            if !borrowed_neo_place.is_prefix_of(&other_neo_place) {
                 self.report_borrow_conflicts_with_destructor(
                     context, borrow, place_span, kind, dropped_ty,
                 );

src/librustc_mir/borrow_check/prefixes.rs

@@ -17,25 +17,6 @@ pub trait IsPrefixOf<'tcx> {
     fn is_prefix_of(&self, other: &Self) -> bool;
 }
 
-impl<'tcx> IsPrefixOf<'tcx> for Place<'tcx> {
-    fn is_prefix_of(&self, other: &Place<'tcx>) -> bool {
-        let mut cursor = other;
-        loop {
-            if self == cursor {
-                return true;
-            }
-
-            match *cursor {
-                Place::Promoted(_) |
-                Place::Local(_) | Place::Static(_) => return false,
-                Place::Projection(ref proj) => {
-                    cursor = &proj.base;
-                }
-            }
-        }
-    }
-}
-
 impl<'tcx> IsPrefixOf<'tcx> for NeoPlace<'tcx> {
     fn is_prefix_of(&self, other: &NeoPlace<'tcx>) -> bool {
         self.base == other.base