check_manual_pattern_char_comparison: avoid indexing and increase readability

Author: AurelienFT

clippy_lints/src/string_patterns.rs

@@ -1,4 +1,3 @@
-use std::cmp::Ordering;
 use std::ops::ControlFlow;
 
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
@@ -18,19 +17,19 @@ use rustc_span::{sym, Span};
 
 declare_clippy_lint! {
     /// ### What it does
-    /// Checks for manual char comparison in string patterns
+    /// Checks for manual `char` comparison in string patterns
     ///
     /// ### Why is this bad?
     /// This can be written more concisely using a `char` or an array of `char`.
     /// This is more readable and more optimized when comparing to only one `char`.
     ///
     /// ### Example
     /// ```no_run
-    /// "Hello World !".trim_end_matches(|c: char| c == '.' || c == ',' || c == '!' || c == '?');
+    /// "Hello World!".trim_end_matches(|c| c == '.' || c == ',' || c == '!' || c == '?');
     /// ```
     /// Use instead:
     /// ```no_run
-    /// "Hello World !".trim_end_matches(['.', ',', '!', '?']);
+    /// "Hello World!".trim_end_matches(['.', ',', '!', '?']);
     /// ```
     #[clippy::version = "1.80.0"]
     pub MANUAL_PATTERN_CHAR_COMPARISON,
@@ -124,10 +123,9 @@ fn get_char_span<'tcx>(cx: &'_ LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Optio
 }
 
 fn check_manual_pattern_char_comparison(cx: &LateContext<'_>, method_arg: &Expr<'_>) {
-    let applicability = Applicability::MachineApplicable;
     if let ExprKind::Closure(closure) = method_arg.kind
         && let body = cx.tcx.hir().body(closure.body)
-        && let PatKind::Binding(_, binding, ..) = body.params[0].pat.kind
+        && let Some(PatKind::Binding(_, binding, ..)) = body.params.first().map(|p| p.pat.kind)
     {
         let mut set_char_spans: Vec<Span> = Vec::new();
 
@@ -185,27 +183,25 @@ fn check_manual_pattern_char_comparison(cx: &LateContext<'_>, method_arg: &Expr<
             MANUAL_PATTERN_CHAR_COMPARISON,
             method_arg.span,
             "this manual char comparison can be written more succinctly",
-            |diag| match set_char_spans.len().cmp(&1) {
-                Ordering::Equal => {
+            |diag| {
+                if let [set_char_span] = set_char_spans[..] {
                     diag.span_suggestion(
                         method_arg.span,
                         "consider using a `char`",
-                        snippet(cx, set_char_spans[0], "c"),
-                        applicability,
+                        snippet(cx, set_char_span, "c"),
+                        Applicability::MachineApplicable,
                     );
-                },
-                Ordering::Greater => {
+                } else {
                     diag.span_suggestion(
                         method_arg.span,
                         "consider using an array of `char`",
                         format!(
                             "[{}]",
                             set_char_spans.into_iter().map(|span| snippet(cx, span, "c")).join(", ")
                         ),
-                        applicability,
+                        Applicability::MachineApplicable,
                     );
-                },
-                Ordering::Less => {},
+                }
             },
         );
     }