1 files changed, 103 insertions, 0 deletions
diff --git a/src/librustdoc/fold.rs b/src/librustdoc/fold.rs
new file mode 100644
index 000000000..6b7e67e2c
--- /dev/null
+++ b/src/librustdoc/fold.rs
@@ -0,0 +1,103 @@
+use crate::clean::*;
+
+pub(crate) fn strip_item(mut item: Item) -> Item {
+    if !matches!(*item.kind, StrippedItem(..)) {
+        item.kind = Box::new(StrippedItem(item.kind));
+    }
+    item
+}
+
+pub(crate) trait DocFolder: Sized {
+    fn fold_item(&mut self, item: Item) -> Option<Item> {
+        Some(self.fold_item_recur(item))
+    }
+
+    /// don't override!
+    fn fold_inner_recur(&mut self, kind: ItemKind) -> ItemKind {
+        match kind {
+            StrippedItem(..) => unreachable!(),
+            ModuleItem(i) => ModuleItem(self.fold_mod(i)),
+            StructItem(mut i) => {
+                i.fields = i.fields.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                StructItem(i)
+            }
+            UnionItem(mut i) => {
+                i.fields = i.fields.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                UnionItem(i)
+            }
+            EnumItem(mut i) => {
+                i.variants = i.variants.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                EnumItem(i)
+            }
+            TraitItem(mut i) => {
+                i.items = i.items.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                TraitItem(i)
+            }
+            ImplItem(mut i) => {
+                i.items = i.items.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                ImplItem(i)
+            }
+            VariantItem(i) => match i {
+                Variant::Struct(mut j) => {
+                    j.fields = j.fields.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                    VariantItem(Variant::Struct(j))
+                }
+                Variant::Tuple(fields) => {
+                    let fields = fields.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                    VariantItem(Variant::Tuple(fields))
+                }
+                Variant::CLike => VariantItem(Variant::CLike),
+            },
+            ExternCrateItem { src: _ }
+            | ImportItem(_)
+            | FunctionItem(_)
+            | TypedefItem(_)
+            | OpaqueTyItem(_)
+            | StaticItem(_)
+            | ConstantItem(_)
+            | TraitAliasItem(_)
+            | TyMethodItem(_)
+            | MethodItem(_, _)
+            | StructFieldItem(_)
+            | ForeignFunctionItem(_)
+            | ForeignStaticItem(_)
+            | ForeignTypeItem
+            | MacroItem(_)
+            | ProcMacroItem(_)
+            | PrimitiveItem(_)
+            | TyAssocConstItem(..)
+            | AssocConstItem(..)
+            | TyAssocTypeItem(..)
+            | AssocTypeItem(..)
+            | KeywordItem => kind,
+        }
+    }
+
+    /// don't override!
+    fn fold_item_recur(&mut self, mut item: Item) -> Item {
+        item.kind = Box::new(match *item.kind {
+            StrippedItem(box i) => StrippedItem(Box::new(self.fold_inner_recur(i))),
+            _ => self.fold_inner_recur(*item.kind),
+        });
+        item
+    }
+
+    fn fold_mod(&mut self, m: Module) -> Module {
+        Module {
+            span: m.span,
+            items: m.items.into_iter().filter_map(|i| self.fold_item(i)).collect(),
+        }
+    }
+
+    fn fold_crate(&mut self, mut c: Crate) -> Crate {
+        c.module = self.fold_item(c.module).unwrap();
+
+        let external_traits = { std::mem::take(&mut *c.external_traits.borrow_mut()) };
+        for (k, mut v) in external_traits {
+            v.trait_.items = v.trait_.items.into_iter().filter_map(|i| self.fold_item(i)).collect();
+            c.external_traits.borrow_mut().insert(k, v);
+        }
+
+        c
+    }
+}