Remove one more usage of mk_substs_trait

compiler/rustc_middle/src/mir/mod.rs

@@ -1847,7 +1847,7 @@ impl<'tcx> Operand<'tcx> {
     pub fn function_handle(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        substs: impl IntoIterator<Item = GenericArg<'tcx>>,
         span: Span,
     ) -> Self {
         let ty = tcx.mk_fn_def(def_id, substs);

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -142,7 +142,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let exchange_malloc = Operand::function_handle(
                     tcx,
                     tcx.require_lang_item(LangItem::ExchangeMalloc, Some(expr_span)),
-                    ty::List::empty(),
+                    [],
                     expr_span,
                 );
                 let storage = this.temp(tcx.mk_mut_ptr(tcx.types.u8), expr_span);

compiler/rustc_mir_dataflow/src/elaborate_drops.rs

@@ -614,7 +614,6 @@ where
         let drop_trait = tcx.require_lang_item(LangItem::Drop, None);
         let drop_fn = tcx.associated_item_def_ids(drop_trait)[0];
         let ty = self.place_ty(self.place);
-        let substs = tcx.mk_substs_trait(ty, []);
 
         let ref_ty =
             tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut { ty, mutbl: hir::Mutability::Mut });
@@ -632,7 +631,12 @@ where
             )],
             terminator: Some(Terminator {
                 kind: TerminatorKind::Call {
-                    func: Operand::function_handle(tcx, drop_fn, substs, self.source_info.span),
+                    func: Operand::function_handle(
+                        tcx,
+                        drop_fn,
+                        [ty.into()],
+                        self.source_info.span,
+                    ),
                     args: vec![Operand::Move(Place::from(ref_place))],
                     destination: unit_temp,
                     target: Some(succ),