minor fix

Author: ding-young

src/items.rs

@@ -2115,7 +2115,10 @@ impl Rewrite for ast::FnRetTy {
                         .checked_sub(arrow_width)
                         .max_width_error(shape.width, self.span())?;
                     return ty
-                        .rewrite_result(context, Shape::legacy(inner_width, shape.indent + 3))
+                        .rewrite_result(
+                            context,
+                            Shape::legacy(inner_width, shape.indent + arrow_width),
+                        )
                         .map(|r| format!("-> {}", r));
                 }
 

src/rewrite.rs

@@ -20,7 +20,7 @@ pub(crate) trait Rewrite {
     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String>;
 
     fn rewrite_result(&self, context: &RewriteContext<'_>, shape: Shape) -> RewriteResult {
-        self.rewrite(context, shape).ok_or(RewriteError::Unknown)
+        self.rewrite(context, shape).unknown_error()
     }
 }