use ty::Binder in rustdoc instead of skip_binder

compiler/rustc_middle/src/ty/sty.rs

@@ -980,8 +980,12 @@ where
     /// contain any bound vars that would be bound by the
     /// binder. This is commonly used to 'inject' a value T into a
     /// different binding level.
+    #[track_caller]
     pub fn dummy(value: T) -> Binder<'tcx, T> {
-        assert!(!value.has_escaping_bound_vars());
+        assert!(
+            !value.has_escaping_bound_vars(),
+            "`{value:?}` has escaping bound vars, so it cannot be wrapped in a dummy binder."
+        );
         Binder(value, ty::List::empty())
     }
 
@@ -1128,6 +1132,13 @@ impl<'tcx, T> Binder<'tcx, Option<T>> {
     }
 }
 
+impl<'tcx, T: IntoIterator> Binder<'tcx, T> {
+    pub fn iter(self) -> impl Iterator<Item = ty::Binder<'tcx, T::Item>> {
+        let bound_vars = self.1;
+        self.0.into_iter().map(|v| Binder(v, bound_vars))
+    }
+}
+
 /// Represents the projection of an associated type. In explicit UFCS
 /// form this would be written `<T as Trait<..>>::N`.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]

src/librustdoc/clean/auto_trait.rs

@@ -44,7 +44,7 @@ where
         discard_positive_impl: bool,
     ) -> Option<Item> {
         let tcx = self.cx.tcx;
-        let trait_ref = tcx.mk_trait_ref(trait_def_id, [ty]);
+        let trait_ref = ty::Binder::dummy(tcx.mk_trait_ref(trait_def_id, [ty]));
         if !self.cx.generated_synthetics.insert((ty, trait_def_id)) {
             debug!("get_auto_trait_impl_for({:?}): already generated, aborting", trait_ref);
             return None;
@@ -124,7 +124,7 @@ where
                 unsafety: hir::Unsafety::Normal,
                 generics: new_generics,
                 trait_: Some(clean_trait_ref_with_bindings(self.cx, trait_ref, ThinVec::new())),
-                for_: clean_middle_ty(ty, self.cx, None),
+                for_: clean_middle_ty(ty::Binder::dummy(ty), self.cx, None),
                 items: Vec::new(),
                 polarity,
                 kind: ImplKind::Auto,

src/librustdoc/clean/blanket_impl.rs

@@ -105,10 +105,10 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                         // the post-inference `trait_ref`, as it's more accurate.
                         trait_: Some(clean_trait_ref_with_bindings(
                             cx,
-                            trait_ref.0,
+                            ty::Binder::dummy(trait_ref.0),
                             ThinVec::new(),
                         )),
-                        for_: clean_middle_ty(ty.0, cx, None),
+                        for_: clean_middle_ty(ty::Binder::dummy(ty.0), cx, None),
                         items: cx
                             .tcx
                             .associated_items(impl_def_id)
@@ -117,7 +117,7 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                             .collect::<Vec<_>>(),
                         polarity: ty::ImplPolarity::Positive,
                         kind: ImplKind::Blanket(Box::new(clean_middle_ty(
-                            trait_ref.0.self_ty(),
+                            ty::Binder::dummy(trait_ref.0.self_ty()),
                             cx,
                             None,
                         ))),

src/librustdoc/clean/inline.rs

@@ -293,7 +293,7 @@ fn build_union(cx: &mut DocContext<'_>, did: DefId) -> clean::Union {
 
 fn build_type_alias(cx: &mut DocContext<'_>, did: DefId) -> Box<clean::Typedef> {
     let predicates = cx.tcx.explicit_predicates_of(did);
-    let type_ = clean_middle_ty(cx.tcx.type_of(did), cx, Some(did));
+    let type_ = clean_middle_ty(ty::Binder::dummy(cx.tcx.type_of(did)), cx, Some(did));
 
     Box::new(clean::Typedef {
         type_,
@@ -405,7 +405,7 @@ pub(crate) fn build_impl(
 
     let for_ = match &impl_item {
         Some(impl_) => clean_ty(impl_.self_ty, cx),
-        None => clean_middle_ty(tcx.type_of(did), cx, Some(did)),
+        None => clean_middle_ty(ty::Binder::dummy(tcx.type_of(did)), cx, Some(did)),
     };
 
     // Only inline impl if the implementing type is
@@ -496,7 +496,8 @@ pub(crate) fn build_impl(
         ),
     };
     let polarity = tcx.impl_polarity(did);
-    let trait_ = associated_trait.map(|t| clean_trait_ref_with_bindings(cx, t, ThinVec::new()));
+    let trait_ = associated_trait
+        .map(|t| clean_trait_ref_with_bindings(cx, ty::Binder::dummy(t), ThinVec::new()));
     if trait_.as_ref().map(|t| t.def_id()) == tcx.lang_items().deref_trait() {
         super::build_deref_target_impls(cx, &trait_items, ret);
     }
@@ -640,14 +641,14 @@ pub(crate) fn print_inlined_const(tcx: TyCtxt<'_>, did: DefId) -> String {
 
 fn build_const(cx: &mut DocContext<'_>, def_id: DefId) -> clean::Constant {
     clean::Constant {
-        type_: clean_middle_ty(cx.tcx.type_of(def_id), cx, Some(def_id)),
+        type_: clean_middle_ty(ty::Binder::dummy(cx.tcx.type_of(def_id)), cx, Some(def_id)),
         kind: clean::ConstantKind::Extern { def_id },
     }
 }
 
 fn build_static(cx: &mut DocContext<'_>, did: DefId, mutable: bool) -> clean::Static {
     clean::Static {
-        type_: clean_middle_ty(cx.tcx.type_of(did), cx, Some(did)),
+        type_: clean_middle_ty(ty::Binder::dummy(cx.tcx.type_of(did)), cx, Some(did)),
         mutability: if mutable { Mutability::Mut } else { Mutability::Not },
         expr: None,
     }

src/librustdoc/clean/types.rs

@@ -1343,7 +1343,7 @@ pub(crate) enum GenericBound {
 impl GenericBound {
     pub(crate) fn maybe_sized(cx: &mut DocContext<'_>) -> GenericBound {
         let did = cx.tcx.require_lang_item(LangItem::Sized, None);
-        let empty = cx.tcx.intern_substs(&[]);
+        let empty = ty::Binder::dummy(ty::InternalSubsts::empty());
         let path = external_path(cx, did, false, ThinVec::new(), empty);
         inline::record_extern_fqn(cx, did, ItemType::Trait);
         GenericBound::TraitBound(

src/librustdoc/clean/utils.rs

@@ -78,21 +78,29 @@ pub(crate) fn krate(cx: &mut DocContext<'_>) -> Crate {
 
 pub(crate) fn substs_to_args<'tcx>(
     cx: &mut DocContext<'tcx>,
-    substs: &[ty::subst::GenericArg<'tcx>],
+    substs: ty::Binder<'tcx, &[ty::subst::GenericArg<'tcx>]>,
     mut skip_first: bool,
 ) -> Vec<GenericArg> {
     let mut ret_val =
-        Vec::with_capacity(substs.len().saturating_sub(if skip_first { 1 } else { 0 }));
-    ret_val.extend(substs.iter().filter_map(|kind| match kind.unpack() {
+        Vec::with_capacity(substs.skip_binder().len().saturating_sub(if skip_first {
+            1
+        } else {
+            0
+        }));
+    ret_val.extend(substs.iter().filter_map(|kind| match kind.skip_binder().unpack() {
         GenericArgKind::Lifetime(lt) => {
             Some(GenericArg::Lifetime(clean_middle_region(lt).unwrap_or(Lifetime::elided())))
         }
         GenericArgKind::Type(_) if skip_first => {
             skip_first = false;
             None
         }
-        GenericArgKind::Type(ty) => Some(GenericArg::Type(clean_middle_ty(ty, cx, None))),
-        GenericArgKind::Const(ct) => Some(GenericArg::Const(Box::new(clean_middle_const(ct, cx)))),
+        GenericArgKind::Type(ty) => {
+            Some(GenericArg::Type(clean_middle_ty(kind.rebind(ty), cx, None)))
+        }
+        GenericArgKind::Const(ct) => {
+            Some(GenericArg::Const(Box::new(clean_middle_const(kind.rebind(ct), cx))))
+        }
     }));
     ret_val
 }
@@ -102,15 +110,20 @@ fn external_generic_args<'tcx>(
     did: DefId,
     has_self: bool,
     bindings: ThinVec<TypeBinding>,
-    substs: SubstsRef<'tcx>,
+    substs: ty::Binder<'tcx, SubstsRef<'tcx>>,
 ) -> GenericArgs {
-    let args = substs_to_args(cx, substs, has_self);
+    let args = substs_to_args(cx, substs.map_bound(|substs| &substs[..]), has_self);
 
     if cx.tcx.fn_trait_kind_from_def_id(did).is_some() {
+        let ty = substs
+            .iter()
+            .nth(if has_self { 1 } else { 0 })
+            .unwrap()
+            .map_bound(|arg| arg.expect_ty());
         let inputs =
             // The trait's first substitution is the one after self, if there is one.
-            match substs.iter().nth(if has_self { 1 } else { 0 }).unwrap().expect_ty().kind() {
-                ty::Tuple(tys) => tys.iter().map(|t| clean_middle_ty(t, cx, None)).collect::<Vec<_>>().into(),
+            match ty.skip_binder().kind() {
+                ty::Tuple(tys) => tys.iter().map(|t| clean_middle_ty(ty.rebind(t), cx, None)).collect::<Vec<_>>().into(),
                 _ => return GenericArgs::AngleBracketed { args: args.into(), bindings },
             };
         let output = bindings.into_iter().next().and_then(|binding| match binding.kind {
@@ -130,7 +143,7 @@ pub(super) fn external_path<'tcx>(
     did: DefId,
     has_self: bool,
     bindings: ThinVec<TypeBinding>,
-    substs: SubstsRef<'tcx>,
+    substs: ty::Binder<'tcx, SubstsRef<'tcx>>,
 ) -> Path {
     let def_kind = cx.tcx.def_kind(did);
     let name = cx.tcx.item_name(did);