Reduce direct mk_ty usage.

We use more specific `mk_*` functions in most places, might as well use
them as much as possible.

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -193,7 +193,7 @@ fn get_info_on_unsized_field<'tcx>(
 
     // Have to adjust type for ty::Str
     let unsized_inner_ty = match unsized_inner_ty.kind() {
-        ty::Str => tcx.mk_ty(ty::Uint(ty::UintTy::U8)),
+        ty::Str => tcx.types.u8,
         _ => unsized_inner_ty,
     };
 
@@ -216,7 +216,7 @@ fn create_pointee_place<'tcx>(
 
         let (unsized_inner_ty, num_elems) = get_info_on_unsized_field(ty, valtree, tcx);
         let unsized_inner_ty = match unsized_inner_ty.kind() {
-            ty::Str => tcx.mk_ty(ty::Uint(ty::UintTy::U8)),
+            ty::Str => tcx.types.u8,
             _ => unsized_inner_ty,
         };
         let unsized_inner_ty_size =

compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs

@@ -217,10 +217,10 @@ impl Qualif for CustomEq {
 
     fn in_adt_inherently<'tcx>(
         cx: &ConstCx<'_, 'tcx>,
-        adt: AdtDef<'tcx>,
+        def: AdtDef<'tcx>,
         substs: SubstsRef<'tcx>,
     ) -> bool {
-        let ty = cx.tcx.mk_ty(ty::Adt(adt, substs));
+        let ty = cx.tcx.mk_adt(def, substs);
         !ty.is_structural_eq_shallow(cx.tcx)
     }
 }