Apply derivable_impls to Clippy itself

Author: profetia

clippy_lints/src/matches/significant_drop_in_scrutinee.rs

@@ -226,11 +226,12 @@ impl<'a, 'tcx> SigDropChecker<'a, 'tcx> {
     }
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Default)]
 enum SigDropHolder {
     /// No values with significant drop present in this expression.
     ///
     /// Expressions that we've emitted lints do not count.
+    #[default]
     None,
     /// Some field in this expression references to values with significant drop.
     ///
@@ -244,12 +245,6 @@ enum SigDropHolder {
     Moved,
 }
 
-impl Default for SigDropHolder {
-    fn default() -> Self {
-        Self::None
-    }
-}
-
 struct SigDropHelper<'a, 'tcx> {
     cx: &'a LateContext<'tcx>,
     parent_expr: Option<&'tcx Expr<'tcx>>,