Fix issue rust-lang#43481: emit the EndRegion *before* StorageDeads for a scope.

(The idea is that the StorageDead marks the point where the memory can
be deallocated, and the EndRegion is marking where borrows of that
memory can no longer legally exist.)

Author: pnkfelix

src/librustc_mir/build/scope.rs

@@ -352,14 +352,15 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         }
         let scope = self.scopes.pop().unwrap();
         assert_eq!(scope.region_scope, region_scope.0);
+
+        self.cfg.push_end_region(self.hir.tcx(), block, region_scope.1, scope.region_scope);
         unpack!(block = build_scope_drops(&mut self.cfg,
                                           &scope,
                                           &self.scopes,
                                           block,
                                           self.arg_count,
                                           false));
 
-        self.cfg.push_end_region(self.hir.tcx(), block, region_scope.1, scope.region_scope);
         block.unit()
     }
 
@@ -406,15 +407,16 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 scope.cached_exits.insert((target, region_scope.0), b);
                 b
             };
+
+            // End all regions for scopes out of which we are breaking.
+            self.cfg.push_end_region(self.hir.tcx(), block, region_scope.1, scope.region_scope);
+
             unpack!(block = build_scope_drops(&mut self.cfg,
                                               scope,
                                               rest,
                                               block,
                                               self.arg_count,
                                               false));
-
-            // End all regions for scopes out of which we are breaking.
-            self.cfg.push_end_region(self.hir.tcx(), block, region_scope.1, scope.region_scope);
         }
         }
         let scope = &self.scopes[len - scope_count];