Avoid ref when using format!

Clean up a few minor refs in `format!` macro, as it has a performance cost. Apparently the compiler is unable to inline `format!("{}", &variable)`, and does a run-time double-reference instead (format macro already does one level referencing).

Inlining format args prevents accidental `&` misuse.

Author: nyurik

clippy_lints/src/approx_const.rs

@@ -97,7 +97,7 @@ impl ApproxConstant {
                         cx,
                         APPROX_CONSTANT,
                         e.span,
-                        format!("approximate value of `{module}::consts::{}` found", &name),
+                        format!("approximate value of `{module}::consts::{name}` found"),
                         None,
                         "consider using the constant directly",
                     );

clippy_lints/src/default.rs

@@ -221,7 +221,7 @@ impl<'tcx> LateLintPass<'tcx> for Default {
                         .map(ToString::to_string)
                         .collect::<Vec<_>>()
                         .join(", ");
-                    format!("{adt_def_ty_name}::<{}>", &tys_str)
+                    format!("{adt_def_ty_name}::<{tys_str}>")
                 } else {
                     binding_type.to_string()
                 };

clippy_lints/src/methods/open_options.rs

@@ -151,7 +151,7 @@ fn check_open_options(cx: &LateContext<'_>, settings: &[(OpenOption, Argument, S
                 cx,
                 NONSENSICAL_OPEN_OPTIONS,
                 prev_span,
-                format!("the method `{}` is called more than once", &option),
+                format!("the method `{option}` is called more than once"),
             );
         }
     }

clippy_lints/src/methods/wrong_self_convention.rs

@@ -127,7 +127,7 @@ pub(super) fn check<'tcx>(
                         .collect::<Vec<_>>()
                         .join(" and ");
 
-                    format!("methods with the following characteristics: ({})", &s)
+                    format!("methods with the following characteristics: ({s})")
                 } else {
                     format!("methods called {}", &conventions[0])
                 }

clippy_lints/src/no_effect.rs

@@ -272,7 +272,7 @@ fn check_unnecessary_operation(cx: &LateContext<'_>, stmt: &Stmt<'_>) {
             }
             let snippet =
                 if let (Some(arr), Some(func)) = (snippet_opt(cx, reduced[0].span), snippet_opt(cx, reduced[1].span)) {
-                    format!("assert!({}.len() > {});", &arr, &func)
+                    format!("assert!({arr}.len() > {func});")
                 } else {
                     return;
                 };

clippy_lints/src/types/borrowed_box.rs

@@ -48,15 +48,15 @@ pub(super) fn check(cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, lt: &Lifetime, m
                 let inner_snippet = snippet(cx, inner.span, "..");
                 let suggestion = match &inner.kind {
                     TyKind::TraitObject(bounds, lt_bound, _) if bounds.len() > 1 || !lt_bound.is_elided() => {
-                        format!("&{ltopt}({})", &inner_snippet)
+                        format!("&{ltopt}({inner_snippet})")
                     },
                     TyKind::Path(qpath)
                         if get_bounds_if_impl_trait(cx, qpath, inner.hir_id)
                             .map_or(false, |bounds| bounds.len() > 1) =>
                     {
-                        format!("&{ltopt}({})", &inner_snippet)
+                        format!("&{ltopt}({inner_snippet})")
                     },
-                    _ => format!("&{ltopt}{}", &inner_snippet),
+                    _ => format!("&{ltopt}{inner_snippet}"),
                 };
                 span_lint_and_sugg(
                     cx,