filter out derive helper attributes during ast lowering but keeping them for rustdoc

compiler/rustc_attr_parsing/src/interface.rs

@@ -292,6 +292,11 @@ impl<'sess> AttributeParser<'sess> {
         mut emit_lint: impl FnMut(LintId, MultiSpan, EmitAttribute),
     ) -> Vec<Attribute> {
         let mut attributes = Vec::new();
+        // We store the attributes we intend to discard at the end of this function in order to
+        // check they are applied to the right target and error out if necessary. In practice, we
+        // end up dropping only derive attributes and derive helpers, both being fully processed
+        // at macro expansion.
+        let mut dropped_attributes = Vec::new();
         let mut attr_paths: Vec<RefPathParser<'_>> = Vec::new();
         let mut early_parsed_state = EarlyParsedState::default();
 
@@ -452,7 +457,19 @@ impl<'sess> AttributeParser<'sess> {
                             self.check_invalid_crate_level_attr_item(&attr, inner_span);
                         }
 
-                        attributes.push(Attribute::Unparsed(Box::new(attr)));
+                        let attr = Attribute::Unparsed(Box::new(attr));
+
+                        if self.sess.opts.actually_rustdoc
+                            || self.tools.is_some_and(|t| t.iter().any(|i| i.name == parts[0]))
+                            // FIXME: this can be removed once #152369 has been merged.
+                            // https://github.com/rust-lang/rust/pull/152369
+                            || [sym::allow, sym::deny, sym::expect, sym::forbid, sym::warn]
+                                .contains(&parts[0])
+                        {
+                            attributes.push(attr);
+                        } else {
+                            dropped_attributes.push(attr);
+                        }
                     };
                 }
             }
@@ -476,7 +493,7 @@ impl<'sess> AttributeParser<'sess> {
         }
 
         if !matches!(self.should_emit, ShouldEmit::Nothing) && target == Target::WherePredicate {
-            self.check_invalid_where_predicate_attrs(attributes.iter());
+            self.check_invalid_where_predicate_attrs(attributes.iter().chain(&dropped_attributes));
         }
 
         attributes