misc: use Symbols instead of &strs

clippy_lints/src/methods/manual_saturating_arithmetic.rs

@@ -8,6 +8,7 @@ use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_lint::LateContext;
 use rustc_middle::ty::layout::LayoutOf;
+use rustc_span::Symbol;
 
 pub fn check(
     cx: &LateContext<'_>,
@@ -15,7 +16,7 @@ pub fn check(
     arith_lhs: &hir::Expr<'_>,
     arith_rhs: &hir::Expr<'_>,
     unwrap_arg: &hir::Expr<'_>,
-    arith: &str,
+    arith: Symbol,
 ) {
     let ty = cx.typeck_results().expr_ty(arith_lhs);
     if !ty.is_integral() {
@@ -26,35 +27,43 @@ pub fn check(
         return;
     };
 
-    if ty.is_signed() {
+    let Some(checked_arith) = CheckedArith::new(arith) else {
+        return;
+    };
+
+    {
         use self::MinMax::{Max, Min};
         use self::Sign::{Neg, Pos};
+        use CheckedArith::{Add, Mul, Sub};
 
-        let Some(sign) = lit_sign(arith_rhs) else {
-            return;
-        };
+        if ty.is_signed() {
+            let Some(sign) = lit_sign(arith_rhs) else {
+                return;
+            };
 
-        match (arith, sign, mm) {
-            ("add", Pos, Max) | ("add", Neg, Min) | ("sub", Neg, Max) | ("sub", Pos, Min) => (),
-            // "mul" is omitted because lhs can be negative.
-            _ => return,
-        }
-    } else {
-        match (mm, arith) {
-            (MinMax::Max, "add" | "mul") | (MinMax::Min, "sub") => (),
-            _ => return,
+            match (&checked_arith, sign, mm) {
+                (Add, Pos, Max) | (Add, Neg, Min) | (Sub, Neg, Max) | (Sub, Pos, Min) => (),
+                // "mul" is omitted because lhs can be negative.
+                _ => return,
+            }
+        } else {
+            match (mm, &checked_arith) {
+                (Max, Add | Mul) | (Min, Sub) => (),
+                _ => return,
+            }
         }
     }
 
     let mut applicability = Applicability::MachineApplicable;
+    let saturating_arith = checked_arith.as_saturating();
     span_lint_and_sugg(
         cx,
         super::MANUAL_SATURATING_ARITHMETIC,
         expr.span,
         "manual saturating arithmetic",
-        format!("consider using `saturating_{arith}`"),
+        format!("consider using `{saturating_arith}`"),
         format!(
-            "{}.saturating_{arith}({})",
+            "{}.{saturating_arith}({})",
             snippet_with_applicability(cx, arith_lhs.span, "..", &mut applicability),
             snippet_with_applicability(cx, arith_rhs.span, "..", &mut applicability),
         ),
@@ -62,6 +71,32 @@ pub fn check(
     );
 }
 
+enum CheckedArith {
+    Add,
+    Sub,
+    Mul,
+}
+
+impl CheckedArith {
+    fn new(sym: Symbol) -> Option<Self> {
+        let res = match sym {
+            sym::checked_add => Self::Add,
+            sym::checked_sub => Self::Sub,
+            sym::checked_mul => Self::Mul,
+            _ => return None,
+        };
+        Some(res)
+    }
+
+    fn as_saturating(&self) -> &'static str {
+        match self {
+            Self::Add => "saturating_add",
+            Self::Sub => "saturating_sub",
+            Self::Mul => "saturating_mul",
+        }
+    }
+}
+
 #[derive(PartialEq, Eq)]
 enum MinMax {
     Min,

clippy_lints/src/methods/mod.rs

@@ -5507,14 +5507,7 @@ impl Methods {
                 (sym::unwrap_or, [u_arg]) => {
                     match method_call(recv) {
                         Some((arith @ (sym::checked_add | sym::checked_sub | sym::checked_mul), lhs, [rhs], _, _)) => {
-                            manual_saturating_arithmetic::check(
-                                cx,
-                                expr,
-                                lhs,
-                                rhs,
-                                u_arg,
-                                &arith.as_str()[const { "checked_".len() }..],
-                            );
+                            manual_saturating_arithmetic::check(cx, expr, lhs, rhs, u_arg, arith);
                         },
                         Some((sym::map, m_recv, [m_arg], span, _)) => {
                             option_map_unwrap_or::check(cx, expr, m_recv, m_arg, recv, u_arg, span, self.msrv);