1 files changed, 4 insertions, 1 deletions
diff --git a/src/tools/rustfmt/src/attr.rs b/src/tools/rustfmt/src/attr.rs
index 315eb10a9db..a5982820e3d 100644
--- a/src/tools/rustfmt/src/attr.rs
+++ b/src/tools/rustfmt/src/attr.rs
@@ -13,6 +13,7 @@ use crate::lists::{definitive_tactic, itemize_list, write_list, ListFormatting,
 use crate::overflow;
 use crate::rewrite::{Rewrite, RewriteContext};
 use crate::shape::Shape;
+use crate::source_map::SpanUtils;
 use crate::types::{rewrite_path, PathContext};
 use crate::utils::{count_newlines, mk_sp};
 
@@ -116,7 +117,9 @@ fn format_derive(
                 |span| span.lo(),
                 |span| span.hi(),
                 |span| Some(context.snippet(*span).to_owned()),
-                attr.span.lo(),
+                // We update derive attribute spans to start after the opening '('
+                // This helps us focus parsing to just what's inside #[derive(...)]
+                context.snippet_provider.span_after(attr.span, "("),
                 attr.span.hi(),
                 false,
             );