enable clippy::ignored_unit_patterns lint and do fixes

matching over `()` is more explicit, use `()` instead of `_`
for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ignored_unit_patterns

src/from.rs

@@ -61,6 +61,6 @@ impl<T, const N: usize> FromIteratorFixed<T, N> for [T; N] {
         let IteratorFixed { inner: mut it } = iter_fixed;
         // We know that it will yield N elements due to it originating from an IteratorFixed
         // of size N
-        [(); N].map(|_| it.next().unwrap())
+        [(); N].map(|()| it.next().unwrap())
     }
 }

src/lib.rs

@@ -4,6 +4,7 @@
 #![cfg_attr(feature = "nightly_features", feature(generic_const_exprs))]
 // enable additionnal lints
 #![warn(clippy::doc_markdown)]
+#![warn(clippy::ignored_unit_patterns)]
 
 use core::iter;
 
@@ -65,7 +66,7 @@ where
     [(); N]
         .into_iter_fixed()
         .enumerate()
-        .map(move |(i, _)| f(i))
+        .map(move |(i, ())| f(i))
 }
 
 impl<I, const N: usize> IteratorFixed<I, N>