style: include iter_on_single_items (#798)

Cargo.toml

@@ -157,7 +157,6 @@ derive_partial_eq_without_eq = { level = "allow", priority = 1 }
 empty_line_after_doc_comments = { level = "allow", priority = 1 }
 fallible_impl_from = { level = "allow", priority = 1 }
 imprecise_flops = { level = "allow", priority = 1 }
-iter_on_single_items = { level = "allow", priority = 1 }
 missing_const_for_fn = { level = "allow", priority = 1 }
 nonstandard_macro_braces = { level = "allow", priority = 1 }
 option_if_let_else = { level = "allow", priority = 1 }

src/math/field.rs

@@ -236,7 +236,7 @@ mod tests {
             for gen in 1..P - 1 {
                 // every field element != 0 generates the whole field additively
                 let gen = PrimeField::from(gen as i64);
-                let mut generated: HashSet<PrimeField<P>> = [gen].into_iter().collect();
+                let mut generated: HashSet<PrimeField<P>> = std::iter::once(gen).collect();
                 let mut x = gen;
                 for _ in 0..P {
                     x = x + gen;