rustc_index: Add a `ZERO` constant to index types

It is commonly used.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/vtable.rs b/src/vtable.rs
index 86ebf37d105..04e24320f91 100644
--- a/src/vtable.rs
+++ b/src/vtable.rs
@@ -61,7 +61,7 @@ pub(crate) fn get_ptr_and_method_ref<'tcx>(
             if ty.is_dyn_star() {
                 let inner_layout = fx.layout_of(arg.layout().ty.builtin_deref(true).unwrap().ty);
                 let dyn_star = CPlace::for_ptr(Pointer::new(arg.load_scalar(fx)), inner_layout);
-                let ptr = dyn_star.place_field(fx, FieldIdx::new(0)).to_ptr();
+                let ptr = dyn_star.place_field(fx, FieldIdx::ZERO).to_ptr();
                 let vtable =
                     dyn_star.place_field(fx, FieldIdx::new(1)).to_cvalue(fx).load_scalar(fx);
                 break 'block (ptr, vtable);