use free functions instead of Filter::new

Having a ::new on each of the filter types was a bit weird, especially
because we returned Box<dyn ...> instead of Self (and clippy rightfully
complained). With this patch, we now have a bunch of normal functions,
and we don't show to the outside how a filter is actually implemented
(or what struct is behind it).

1 files changed, 6 insertions, 8 deletions

diff --git a/src/filters/mod.rs b/src/filters/mod.rs
index 3d0868b..162b6f8 100644
--- a/src/filters/mod.rs
+++ b/src/filters/mod.rs
@@ -1,4 +1,3 @@
-#![allow(clippy::new_ret_no_self)]
 use std::{fmt, ops};
 
 use num_derive::FromPrimitive;
@@ -74,13 +73,7 @@ pub trait Filter<Early, Late>: Send + Sync + fmt::Debug {
 }
 
 #[derive(Debug, Clone, Copy)]
-pub struct Const(pub bool);
-
-impl Const {
-    pub fn new<E, L>(output: bool) -> Box<dyn Filter<E, L>> {
-        Box::new(Const(output))
-    }
-}
+struct Const(pub bool);
 
 impl<E, L> Filter<E, L> for Const {
     fn filter_early(&self, _: &E) -> Inclusion {
@@ -92,6 +85,11 @@ impl<E, L> Filter<E, L> for Const {
     }
 }
 
+/// Construct a `Filter` that always returns a fixed value.
+pub fn constant<E, L>(output: bool) -> Box<dyn Filter<E, L>> {
+    Box::new(Const(output))
+}
+
 struct AndFilter<E, L>(Box<dyn Filter<E, L>>, Box<dyn Filter<E, L>>);
 
 impl<E, L> Filter<E, L> for AndFilter<E, L> {