useful debugging

Author: xacrimon

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

@@ -60,12 +60,18 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             let elem_ty = prefix[0].ty;
             let prefix_valtree = self.simplify_const_pattern_slice_into_valtree(prefix);
 
+            let project = PlaceElem::Subslice {
+                from: 0 as u64,
+                to: prefix.len() as u64,
+                from_end: false,
+            }; // or use a projection??
+
             let match_pair = self.valtree_to_match_pair(
                 src_path.ty,
                 src_path.span,
                 prefix.len() as u64,
                 prefix_valtree,
-                place.clone(),
+                place.clone_project(project),
                 elem_ty,
             );
 

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

@@ -468,6 +468,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             _ => span_bug!(source_info.span, "invalid type for non-scalar compare: {}", ty),
         };
 
+        tracing::warn!("compare_ty: {:?}", compare_ty);
+
         let eq_def_id =
             self.tcx.require_lang_item(LangItem::MatchLoweredCmp, Some(source_info.span));
         let method = trait_method(self.tcx, eq_def_id, sym::do_match, [compare_ty, compare_ty]);