diff options
| -rw-r--r-- | src/librustc_traits/chalk_context/program_clauses.rs | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/src/librustc_traits/chalk_context/program_clauses.rs b/src/librustc_traits/chalk_context/program_clauses.rs index b604f140762..06da938ceaa 100644 --- a/src/librustc_traits/chalk_context/program_clauses.rs +++ b/src/librustc_traits/chalk_context/program_clauses.rs @@ -280,7 +280,10 @@ fn wf_clause_for_tuple<'tcx>( Some(def_id) => def_id, None => return ty::List::empty(), }; - let sized_implemented = type_list[0..arity - 1].iter() + + // If `arity == 0` (i.e. the unit type) or `arity == 1`, this list of + // hypotheses is actually empty. + let sized_implemented = type_list[0 .. std::cmp::max(arity, 1) - 1].iter() .map(|ty| ty::TraitRef { def_id: sized_trait, substs: tcx.mk_substs_trait(*ty, ty::List::empty()), |