chore(deps): upgrade perfectionist and enable non_exhaustive_error

Bump `perfectionist` past `0.0.0-rc.7` to its current `master`
HEAD, which introduces the `non_exhaustive_error` rule and a
suite of `single_letter_*` rules. Wire `non_exhaustive_error`
in as a deny-level lint at the crate root and address the
violations it surfaces:

- Add `#[non_exhaustive]` to `args::fraction::ConversionError`
  and `args::fraction::FromStrError`.
- Drop the unused `derive_more::Error` derive from
  `bytes_format::parsed_value::ParsedValue`. The enum is a
  formatter return value rather than an error type, so it no
  longer participates in the rule.

The new `single_letter_*` rules also surface unrelated
violations, addressed as follows:

- Rename trait-method parameters `a` / `b` to `path` / `prefix`
  in `app::overlapping_arguments::Api::starts_with`, and rename
  the closure parameter `r` to `range` in `usage_md`.
- Configure the rule's `comparison_methods` allowlist in
  `dylint.toml` to include the project-specific helper
  `sort_reflection_by` and the `into-sorted` crate's
  `into_sorted_by`, both of which take comparison closures
  whose `|a, b|` parameters CLAUDE.md explicitly permits.
- Allow `single_letter_let_binding` at the `args` module level
  because `clap_derive`'s `default_value_t` expansion produces
  a `let s = ...` binding that is outside our control.

Register the `perfectionist` tool and gate the deny directive
on `cfg(dylint_lib = "perfectionist")` so non-dylint builds do
not see an unknown lint tool. Declare the matching `check-cfg`
entry in `Cargo.toml` to keep `unexpected_cfgs` quiet on
ordinary builds.

https://claude.ai/code/session_01CoRidYHvni9nKNgxMPXmfQ

Author: claude

Cargo.toml

@@ -88,6 +88,9 @@ terminal_size = "0.4.4"
 text-block-macros = "0.2.0"
 zero-copy-pads = "0.2.0"
 
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(dylint_lib, values("perfectionist"))'] }
+
 [dev-dependencies]
 build-fs-tree = "0.8.1"
 command-extra = "1.0.0"

dylint.toml

@@ -1,4 +1,31 @@
 [workspace.metadata.dylint]
 libraries = [
-    { git = "https://github.com/KSXGitHub/perfectionist", tag = "0.0.0-rc.7" },
+    { git = "https://github.com/KSXGitHub/perfectionist", rev = "3acd734c12fbd56d2c760f3c7bc9a19e45e62541" },
+]
+
+["perfectionist::single_letter_names"]
+# Treat project-specific and third-party comparison-style helpers as if
+# they were standard `sort_by`-shaped methods, so the idiomatic
+# `|a, b| a.field.cmp(&b.field)` closure does not trip the rule. The
+# defaults are included explicitly because setting this list replaces
+# the built-in allowlist rather than extending it.
+comparison_methods = [
+    "sort_by",
+    "sort_unstable_by",
+    "sort_by_key",
+    "sort_unstable_by_key",
+    "min_by",
+    "max_by",
+    "min_by_key",
+    "max_by_key",
+    "binary_search_by",
+    "binary_search_by_key",
+    "cmp_by",
+    "partial_cmp_by",
+    "eq_by",
+    "fold",
+    # Project-specific helper used in integration tests.
+    "sort_reflection_by",
+    # `into-sorted` crate's consuming sort.
+    "into_sorted_by",
 ]

src/app/overlapping_arguments.rs

@@ -14,7 +14,7 @@ pub trait Api {
     type RealPathError;
     fn canonicalize(path: &Self::Argument) -> Result<Self::RealPath, Self::RealPathError>;
     fn is_real_dir(path: &Self::Argument) -> bool;
-    fn starts_with(a: &Self::RealPath, b: &Self::RealPath) -> bool;
+    fn starts_with(path: &Self::RealPath, prefix: &Self::RealPath) -> bool;
 }
 
 /// Implementation of [`Api`] that interacts with the real system.
@@ -36,8 +36,8 @@ impl Api for RealApi {
     }
 
     #[inline]
-    fn starts_with(a: &Self::RealPath, b: &Self::RealPath) -> bool {
-        a.starts_with(b)
+    fn starts_with(path: &Self::RealPath, prefix: &Self::RealPath) -> bool {
+        path.starts_with(prefix)
     }
 }
 

src/app/overlapping_arguments/test_remove_overlapping_paths.rs

@@ -64,8 +64,8 @@ impl Api for MockedApi {
             .all(|(link, _)| PathBuf::from(link).normalize() != path)
     }
 
-    fn starts_with(a: &Self::RealPath, b: &Self::RealPath) -> bool {
-        a.starts_with(b)
+    fn starts_with(path: &Self::RealPath, prefix: &Self::RealPath) -> bool {
+        path.starts_with(prefix)
     }
 }
 

src/args.rs

@@ -1,3 +1,11 @@
+#![cfg_attr(
+    dylint_lib = "perfectionist",
+    allow(
+        perfectionist::single_letter_let_binding,
+        reason = "the `let s` bindings flagged by this lint originate in `clap_derive` macro expansion of `default_value_t` and are outside our control",
+    )
+)]
+
 pub mod depth;
 pub mod fraction;
 pub mod quantity;

src/args/fraction.rs

@@ -11,6 +11,7 @@ pub struct Fraction(f32);
 
 /// Error that occurs when calling [`Fraction::new`].
 #[derive(Debug, Display, Clone, Copy, PartialEq, Eq, Error)]
+#[non_exhaustive]
 pub enum ConversionError {
     /// Provided value is greater than or equal to 1.
     #[display("greater than or equal to 1")]
@@ -43,6 +44,7 @@ impl TryFrom<f32> for Fraction {
 
 /// Error that occurs when parsing a string as [`Fraction`].
 #[derive(Debug, Display, Clone, PartialEq, Eq, Error)]
+#[non_exhaustive]
 pub enum FromStrError {
     ParseFloatError(ParseFloatError),
     Conversion(ConversionError),

src/bytes_format/parsed_value.rs

@@ -1,7 +1,7 @@
-use derive_more::{Display, Error};
+use derive_more::Display;
 
 /// Return value of [`Formatter::parse_value`](super::Formatter::parse_value).
-#[derive(Debug, Display, Clone, Copy, Error)]
+#[derive(Debug, Display, Clone, Copy)]
 pub enum ParsedValue {
     /// When input value is less than `scale_base`.
     #[display("{value}   ")]

src/lib.rs

@@ -4,6 +4,12 @@
 //! [`tree_builder::TreeBuilder`], [`data_tree::DataTree`], or [`visualizer::Visualizer`].
 
 #![deny(warnings)]
+#![cfg_attr(dylint_lib = "perfectionist", feature(register_tool))]
+#![cfg_attr(dylint_lib = "perfectionist", register_tool(perfectionist))]
+#![cfg_attr(
+    dylint_lib = "perfectionist",
+    deny(perfectionist::non_exhaustive_error)
+)]
 
 #[cfg(feature = "json")]
 pub use serde;

src/usage_md.rs

@@ -85,7 +85,7 @@ fn render_argument(out: &mut String, arg: &Arg) {
         .unwrap_or_else(|| arg.get_id().as_str());
     let is_multiple = arg
         .get_num_args()
-        .map(|r| r.max_values() > 1)
+        .map(|range| range.max_values() > 1)
         .unwrap_or(false);
     let display_name = if arg.is_required_set() {
         if is_multiple {

tests/_utils.rs

@@ -466,7 +466,7 @@ impl<'a> Default for CommandList<'a> {
     /// Initialize a list with one `pdu` command.
     fn default() -> Self {
         CommandRepresentation::default()
-            .pipe(|x| vec![x])
+            .pipe(|command| vec![command])
             .pipe(CommandList)
     }
 }