refactor valtree_to_match_pair for readability

Author: xacrimon

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

@@ -157,9 +157,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         elem_ty: Ty<'tcx>,
     ) -> MatchPairTree<'pat, 'tcx> {
         let tcx = self.tcx;
-        tracing::warn!("source pattern type: {:?}", src_pat_ty);
         let (const_ty, pat_ty) = match src_pat_ty.kind() {
-            // wait is source path the wrong thing to care about?
             ty::Slice(_) => (
                 Ty::new_imm_ref(
                     tcx,
@@ -174,24 +172,21 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     tcx.lifetimes.re_erased,
                     Ty::new_array(tcx, elem_ty, subslice_len),
                 ),
-                Ty::new_array(tcx, elem_ty, subslice_len), // WRONG TYPE with too short array len for the move
+                Ty::new_array(tcx, elem_ty, subslice_len),
             ),
-            _ => todo!(),
+            _ => unreachable!(),
         };
 
-        tracing::warn!("const and new pattern type: {:?}, {:?}", const_ty, pat_ty);
-
-        let r#const = ty::Const::new(tcx, ty::ConstKind::Value(const_ty, valtree));
-        let r#const2 = Const::Ty(const_ty, r#const);
+        let ty_cost = ty::Const::new(tcx, ty::ConstKind::Value(const_ty, valtree));
+        let value = Const::Ty(const_ty, r#ty_cost);
+        let test_case = TestCase::Constant { value };
 
         let pattern = tcx.arena.alloc(Pat {
             ty: pat_ty,
             span,
-            kind: PatKind::Constant { value: Const::Ty(const_ty, r#const) },
+            kind: PatKind::Constant { value },
         });
 
-        let test_case = TestCase::Constant { value: r#const2 };
-
         MatchPairTree {
             place: Some(place.to_place(self)),
             test_case,