refactor: new type for range operands

Author: calebcartwright

rustfmt-core/rustfmt-lib/src/patterns.rs

@@ -55,6 +55,19 @@ fn is_short_pattern_inner(pat: &ast::Pat) -> bool {
     }
 }
 
+struct RangeOperand<'a>(&'a Option<ptr::P<ast::Expr>>);
+
+impl<'a> Rewrite for RangeOperand<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match &self.0 {
+            None => Some("".to_owned()),
+            Some(ref exp) => {
+                exp.rewrite(context, shape)
+            }
+        }
+    }
+}
+
 impl Rewrite for Pat {
     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
         match self.kind {
@@ -180,16 +193,6 @@ impl Rewrite for Pat {
                 }
             }
             PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
-                impl Rewrite for Option<ptr::P<ast::Expr>> {
-                    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
-                        match &self {
-                            None => Some("".to_owned()),
-                            Some(ref exp) => {
-                                exp.rewrite(context, shape)
-                            }
-                        }
-                    }
-                }
                 let infix = match end_kind.node {
                     RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
                     RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
@@ -209,8 +212,8 @@ impl Rewrite for Pat {
                     infix.to_owned()
                 };
                 rewrite_pair(
-                    lhs,
-                    rhs,
+                    &RangeOperand(lhs),
+                    &RangeOperand(rhs),
                     PairParts::infix(&infix),
                     context,
                     shape,