experiment with place code

Author: xacrimon

compiler/rustc_mir_build/src/builder/matches/match_pair.rs

@@ -129,7 +129,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         &mut self,
         base_pat: &'pat Pat<'tcx>,
         match_pairs: &mut Vec<MatchPairTree<'pat, 'tcx>>,
-        place: &PlaceBuilder<'tcx>,
+        place: PlaceBuilder<'tcx>,
         prefix: &'pat [Box<Pat<'tcx>>],
         opt_slice: &'pat Option<Box<Pat<'tcx>>>,
         suffix: &'pat [Box<Pat<'tcx>>],
@@ -158,13 +158,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         if self.is_constant_pattern_subslice(prefix) {
             let elem_ty = prefix[0].ty;
             let prefix_valtree = self.simplify_const_pattern_slice_into_valtree(prefix);
-            // FIXME(jieyouxu): triple check these place calculations!
+            let elem =
+                ProjectionElem::Subslice { from: 0, to: prefix.len() as u64, from_end: false };
             if let Some(match_pair) = self.valtree_to_match_pair(
                 base_pat.ty,
                 base_pat.span,
                 prefix.len() as u64,
                 prefix_valtree,
-                place.base().into(),
+                place.clone_project(elem),
                 elem_ty,
             ) {
                 match_pairs.push(match_pair);
@@ -318,7 +319,7 @@ impl<'pat, 'tcx> MatchPairTree<'pat, 'tcx> {
                 cx.prefix_slice_suffix(
                     pattern,
                     &mut subpairs,
-                    &place_builder,
+                    place_builder,
                     prefix,
                     slice,
                     suffix,
@@ -329,7 +330,7 @@ impl<'pat, 'tcx> MatchPairTree<'pat, 'tcx> {
                 cx.prefix_slice_suffix(
                     pattern,
                     &mut subpairs,
-                    &place_builder,
+                    place_builder,
                     prefix,
                     slice,
                     suffix,