Function rustc_trait_selection::traits::get_vtable_index_of_object_method

pub fn get_vtable_index_of_object_method<'tcx, N>(
    tcx: TyCtxt<'tcx>,
    object: &ImplSourceObjectData<'tcx, N>,
    method_def_id: DefId
) -> Option<usize>

Given an upcast trait object described by object, returns the index of the method method_def_id (which should be part of object.upcast_trait_ref) within the vtable for object.