add comment to use of invocation_parent

rust-lang · Nov 25, 2024 · 51a3ab0 · 51a3ab0
1 parent 99c6d26
commit 51a3ab0
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
@@ -608,6 +608,10 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             if self.cx.sess.opts.incremental.is_some() {
                 for (invoc, _) in invocations.iter_mut() {
                     let expn_id = invoc.expansion_data.id;
+                    // When lowering anon-consts, we may end up with spans whose
+                    // parent is the containing item instead of the anon-const itself.
+                    //
+                    // This shouldn't cause any issues wrt to incremental compilation. 
                     let parent_def = self.cx.resolver.invocation_parent(expn_id);
                     let span = invoc.span_mut();
                     *span = span.with_parent(Some(parent_def));