Update #[allow(_)] macros to lint with new version of clippy

Give all `allow` macros a reason statement, and change the macros to
`expect` where possible

crates/fzn-huub/benches/fzn_huub_benchmarks.rs

@@ -1,4 +1,7 @@
-#![allow(unused_crate_dependencies)]
+#![expect(
+	unused_crate_dependencies,
+	reason = "only dependencies for benchmarking are used in this file"
+)]
 use std::{
 	io::Write,
 	path::{Path, PathBuf},

crates/fzn-huub/src/lib.rs

@@ -495,7 +495,7 @@ impl TryFrom<Arguments> for Cli<io::Stdout, fn() -> io::Stderr> {
 				.map_err(|e| e.to_string())?,
 
 			stdout: io::stdout(),
-			#[allow(trivial_casts)] // Doesn't compile without the cast
+			#[expect(trivial_casts, reason = "doesn't compile without the case")]
 			stderr: io::stderr as fn() -> io::Stderr,
 			ansi_color: true,
 		};

crates/fzn-huub/src/main.rs

@@ -1,4 +1,7 @@
-#![allow(unused_crate_dependencies)]
+#![allow(
+	unused_crate_dependencies,
+	reason = "other dependencies are used in the lib.rs file"
+)]
 use std::{convert::Infallible, fs, path::PathBuf, process::ExitCode};
 
 use fzn_huub::Cli;

crates/fzn-huub/tests/flatzinc_tests.rs

@@ -1,4 +1,7 @@
-#![allow(unused_crate_dependencies)]
+#![expect(
+	unused_crate_dependencies,
+	reason = "only dependencies for testing are used in this file"
+)]
 mod helpers;
 
 #[cfg(test)]

crates/huub/src/actions/explanation.rs

@@ -2,7 +2,6 @@ use crate::{actions::inspection::InspectionActions, BoolView, IntView, LitMeanin
 
 pub(crate) trait ExplanationActions: InspectionActions {
 	fn try_int_lit(&self, var: IntView, meaning: LitMeaning) -> Option<BoolView>;
-	#[allow(unused)] // TODO
 	/// Get a literal that represents the given meaning (that is currently `true`)
 	/// or a relaxation if the literal does not yet exist.
 	fn get_int_lit_relaxed(&mut self, var: IntView, meaning: LitMeaning) -> (BoolView, LitMeaning);

crates/huub/src/actions/propagation.rs

@@ -27,7 +27,7 @@ pub(crate) trait PropagationActions: ExplanationActions + DecisionActions {
 		val: IntVal,
 		reason: impl ReasonBuilder<Self>,
 	) -> Result<(), Conflict>;
-	#[allow(dead_code)] // TODO
+	#[expect(dead_code, reason = "TODO: no current use case in propagators")]
 	fn set_int_val(
 		&mut self,
 		var: IntView,

crates/huub/src/model/bool.rs

@@ -407,7 +407,10 @@ impl From<&BoolView> for BoolExpr {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
-#[allow(variant_size_differences)]
+#[allow(
+	variant_size_differences,
+	reason = "`bool` is smaller than all other variants"
+)]
 pub enum BoolView {
 	Lit(RawLit),
 	Const(bool),

crates/huub/src/model/reformulate.rs

@@ -155,7 +155,10 @@ impl VariableMap {
 		let _ = self.map.insert(index.into(), elem.into());
 	}
 
-	#[allow(dead_code)] // TODO
+	#[expect(
+		dead_code,
+		reason = "TODO: investigate whether this can be used for SAT rewriting"
+	)]
 	pub(crate) fn insert_bool(&mut self, index: RawVar, elem: BoolView) {
 		let _ = self.map.insert(index.into(), elem.into());
 	}

crates/huub/src/solver/engine/int_var.rs

@@ -637,7 +637,10 @@ impl IntVar {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
-#[allow(variant_size_differences)]
+#[allow(
+	variant_size_differences,
+	reason = "TODO: Investigate if using Box improves performance"
+)]
 pub(crate) enum OrderStorage {
 	/// Variables for all inequality conditions are eagerly created and stored in order
 	Eager {

crates/huub/src/solver/engine/queue.rs

@@ -38,26 +38,38 @@ impl<E> PriorityQueue<E> {
 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[repr(u8)]
 pub(crate) enum PriorityLevel {
+	#[allow(
+		dead_code,
+		reason = "TODO: no current propagators are this priority level"
+	)]
 	/// The lowest priority level, all other priority levels are more important
-	#[allow(dead_code)] // TODO
 	Lowest,
 	/// A low level of priority, all apart from one priority level are more
 	/// important
 	Low,
+	#[allow(
+		dead_code,
+		reason = "TODO: no current propagators are this priority level"
+	)]
 	/// A medium level of priority, there are just as many normal priority levels
 	/// more as less important than this one.
-	#[allow(dead_code)] // TODO
 	Medium,
+	#[allow(
+		dead_code,
+		reason = "TODO: no current propagators are this priority level"
+	)]
 	/// A high level of priority, all apart from one normal priority level are
 	/// less important.
-	#[allow(dead_code)] // TODO
 	High,
 	/// The highest normal priority level, this priority level is the most
 	/// important normal level of priority.
 	Highest,
+	#[allow(
+		dead_code,
+		reason = "TODO: no current propagators are this priority level"
+	)]
 	/// An extraordinarily high level of priority, generally used to ensure
 	/// something will happen next.
-	#[allow(dead_code)] // TODO
 	Immediate,
 }
 

crates/huub/src/solver/value.rs

@@ -9,7 +9,7 @@ use crate::{
 };
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
-#[allow(variant_size_differences)]
+#[allow(variant_size_differences, reason = "`Int` cannot be as smal as `Bool`")]
 pub enum Value {
 	Bool(bool),
 	Int(IntVal),

crates/huub/src/solver/view.rs

@@ -58,7 +58,7 @@ impl BoolView {
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
-#[allow(variant_size_differences)]
+#[allow(variant_size_differences, reason = "`Lit` cannot be as smal as `bool`")]
 pub(crate) enum BoolViewInner {
 	Lit(RawLit),
 	Const(bool),