Auto merge of #129244 - cjgillot:opaque-hir, r=compiler-errors

Make opaque types regular HIR nodes

Having opaque types as HIR owner introduces all sorts of complications. This PR proposes to make them regular HIR nodes instead.

I haven't gone through all the test changes yet, so there may be a few surprises.

Many thanks to `@camelid` for the first draft.
Fixes https://github.com/rust-lang/rust/issues/129023

Fixes #129099
Fixes #125843
Fixes #119716
Fixes #121422

12 files changed, 16 insertions, 60 deletions

diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index b79458eaa78..fa73733360c 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1828,13 +1828,8 @@ pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> T
             Array(Box::new(clean_ty(ty, cx)), length.into())
         }
         TyKind::Tup(tys) => Tuple(tys.iter().map(|ty| clean_ty(ty, cx)).collect()),
-        TyKind::OpaqueDef(item_id, _) => {
-            let item = cx.tcx.hir().item(item_id);
-            if let hir::ItemKind::OpaqueTy(ty) = item.kind {
-                ImplTrait(ty.bounds.iter().filter_map(|x| clean_generic_bound(x, cx)).collect())
-            } else {
-                unreachable!()
-            }
+        TyKind::OpaqueDef(ty, _) => {
+            ImplTrait(ty.bounds.iter().filter_map(|x| clean_generic_bound(x, cx)).collect())
         }
         TyKind::Path(_) => clean_qpath(ty, cx),
         TyKind::TraitObject(bounds, lifetime, _) => {
@@ -2736,9 +2731,6 @@ fn clean_maybe_renamed_item<'tcx>(
                 type_: clean_ty(ty, cx),
                 kind: ConstantKind::Local { body: body_id, def_id },
             })),
-            // clean_ty changes types which reference an OpaqueTy item to instead be
-            // an ImplTrait, so it's ok to return nothing here.
-            ItemKind::OpaqueTy(_) => return vec![],
             ItemKind::TyAlias(hir_ty, generics) => {
                 *cx.current_type_aliases.entry(def_id).or_insert(0) += 1;
                 let rustdoc_ty = clean_ty(hir_ty, cx);
diff --git a/src/librustdoc/html/render/span_map.rs b/src/librustdoc/html/render/span_map.rs
index 2143f1ff236..7e1ea5cde83 100644
--- a/src/librustdoc/html/render/span_map.rs
+++ b/src/librustdoc/html/render/span_map.rs
@@ -243,7 +243,6 @@ impl<'tcx> Visitor<'tcx> for SpanMapVisitor<'tcx> {
             | ItemKind::ExternCrate(_)
             | ItemKind::ForeignMod { .. }
             | ItemKind::GlobalAsm(_)
-            | ItemKind::OpaqueTy(_)
             // We already have "visit_mod" above so no need to check it here.
             | ItemKind::Mod(_) => {}
         }
diff --git a/src/librustdoc/visit_ast.rs b/src/librustdoc/visit_ast.rs
index 6defe91d383..f789aca7378 100644
--- a/src/librustdoc/visit_ast.rs
+++ b/src/librustdoc/visit_ast.rs
@@ -505,21 +505,11 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
             | hir::ItemKind::Struct(..)
             | hir::ItemKind::Union(..)
             | hir::ItemKind::TyAlias(..)
-            | hir::ItemKind::OpaqueTy(hir::OpaqueTy {
-                origin: hir::OpaqueTyOrigin::TyAlias { .. },
-                ..
-            })
             | hir::ItemKind::Static(..)
             | hir::ItemKind::Trait(..)
             | hir::ItemKind::TraitAlias(..) => {
                 self.add_to_current_mod(item, renamed, import_id);
             }
-            hir::ItemKind::OpaqueTy(hir::OpaqueTy {
-                origin: hir::OpaqueTyOrigin::AsyncFn { .. } | hir::OpaqueTyOrigin::FnReturn { .. },
-                ..
-            }) => {
-                // return-position impl traits are never nameable, and should never be documented.
-            }
             hir::ItemKind::Const(..) => {
                 // Underscore constants do not correspond to a nameable item and
                 // so are never useful in documentation.
diff --git a/src/tools/clippy/clippy_lints/src/extra_unused_type_parameters.rs b/src/tools/clippy/clippy_lints/src/extra_unused_type_parameters.rs
index 796af851bac..6ad879b9fe7 100644
--- a/src/tools/clippy/clippy_lints/src/extra_unused_type_parameters.rs
+++ b/src/tools/clippy/clippy_lints/src/extra_unused_type_parameters.rs
@@ -6,7 +6,7 @@ use rustc_errors::Applicability;
 use rustc_hir::intravisit::{Visitor, walk_impl_item, walk_item, walk_param_bound, walk_ty};
 use rustc_hir::{
     BodyId, ExprKind, GenericBound, GenericParam, GenericParamKind, Generics, ImplItem, ImplItemKind, Item, ItemKind,
-    PredicateOrigin, Ty, TyKind, WherePredicate,
+    PredicateOrigin, Ty, WherePredicate,
 };
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::hir::nested_filter;
@@ -199,12 +199,6 @@ impl<'tcx> Visitor<'tcx> for TypeWalker<'_, 'tcx> {
     fn visit_ty(&mut self, t: &'tcx Ty<'tcx>) {
         if let Some((def_id, _)) = t.peel_refs().as_generic_param() {
             self.ty_params.remove(&def_id);
-        } else if let TyKind::OpaqueDef(id, _) = t.kind {
-            // Explicitly walk OpaqueDef. Normally `walk_ty` would do the job, but it calls
-            // `visit_nested_item`, which checks that `Self::NestedFilter::INTER` is set. We're
-            // using `OnlyBodies`, so the check ends up failing and the type isn't fully walked.
-            let item = self.nested_visit_map().item(id);
-            walk_item(self, item);
         } else {
             walk_ty(self, t);
         }
diff --git a/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs b/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
index 6794c6cabfe..5f349d78053 100644
--- a/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
+++ b/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
@@ -3,7 +3,7 @@ use clippy_utils::source::snippet;
 use rustc_errors::{Applicability, SuggestionStyle};
 use rustc_hir::def_id::DefId;
 use rustc_hir::{
-    AssocItemConstraint, GenericArg, GenericBound, GenericBounds, ItemKind, PredicateOrigin, TraitBoundModifier,
+    AssocItemConstraint, GenericArg, GenericBound, GenericBounds, PredicateOrigin, TraitBoundModifier,
     TyKind, WherePredicate,
 };
 use rustc_hir_analysis::lower_ty;
@@ -342,11 +342,8 @@ impl<'tcx> LateLintPass<'tcx> for ImpliedBoundsInImpls {
         }
     }
 
-    fn check_ty(&mut self, cx: &LateContext<'_>, ty: &rustc_hir::Ty<'_>) {
-        if let TyKind::OpaqueDef(item_id, ..) = ty.kind
-            && let item = cx.tcx.hir().item(item_id)
-            && let ItemKind::OpaqueTy(opaque_ty) = item.kind
-        {
+    fn check_ty(&mut self, cx: &LateContext<'tcx>, ty: &rustc_hir::Ty<'tcx>) {
+        if let TyKind::OpaqueDef(opaque_ty, ..) = ty.kind {
             check(cx, opaque_ty.bounds);
         }
     }
diff --git a/src/tools/clippy/clippy_lints/src/len_zero.rs b/src/tools/clippy/clippy_lints/src/len_zero.rs
index 45346cd18a6..311bbce14bd 100644
--- a/src/tools/clippy/clippy_lints/src/len_zero.rs
+++ b/src/tools/clippy/clippy_lints/src/len_zero.rs
@@ -308,11 +308,7 @@ enum LenOutput {
 
 fn extract_future_output<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<&'tcx PathSegment<'tcx>> {
     if let ty::Alias(_, alias_ty) = ty.kind()
-        && let Some(Node::Item(item)) = cx.tcx.hir().get_if_local(alias_ty.def_id)
-        && let Item {
-            kind: ItemKind::OpaqueTy(opaque),
-            ..
-        } = item
+        && let Some(Node::OpaqueTy(opaque)) = cx.tcx.hir().get_if_local(alias_ty.def_id)
         && let OpaqueTyOrigin::AsyncFn { .. } = opaque.origin
         && let [GenericBound::Trait(trait_ref, _)] = &opaque.bounds
         && let Some(segment) = trait_ref.trait_ref.path.segments.last()
diff --git a/src/tools/clippy/clippy_lints/src/lifetimes.rs b/src/tools/clippy/clippy_lints/src/lifetimes.rs
index 5c37e735445..7c3ef98fd74 100644
--- a/src/tools/clippy/clippy_lints/src/lifetimes.rs
+++ b/src/tools/clippy/clippy_lints/src/lifetimes.rs
@@ -6,7 +6,7 @@ use rustc_errors::Applicability;
 use rustc_hir::FnRetTy::Return;
 use rustc_hir::intravisit::nested_filter::{self as hir_nested_filter, NestedFilter};
 use rustc_hir::intravisit::{
-    Visitor, walk_fn_decl, walk_generic_args, walk_generics, walk_impl_item_ref, walk_item, walk_param_bound,
+    Visitor, walk_fn_decl, walk_generic_args, walk_generics, walk_impl_item_ref, walk_param_bound,
     walk_poly_trait_ref, walk_trait_ref, walk_ty, walk_where_predicate,
 };
 use rustc_hir::{
@@ -420,11 +420,9 @@ impl<'tcx> Visitor<'tcx> for RefVisitor<'_, 'tcx> {
 
     fn visit_ty(&mut self, ty: &'tcx Ty<'_>) {
         match ty.kind {
-            TyKind::OpaqueDef(item, bounds) => {
-                let map = self.cx.tcx.hir();
-                let item = map.item(item);
+            TyKind::OpaqueDef(opaque, bounds) => {
                 let len = self.lts.len();
-                walk_item(self, item);
+                self.visit_opaque_ty(opaque);
                 self.lts.truncate(len);
                 self.lts.extend(bounds.iter().filter_map(|bound| match bound {
                     GenericArg::Lifetime(&l) => Some(l),
diff --git a/src/tools/clippy/clippy_lints/src/manual_async_fn.rs b/src/tools/clippy/clippy_lints/src/manual_async_fn.rs
index 7097c85156c..81115cffdca 100644
--- a/src/tools/clippy/clippy_lints/src/manual_async_fn.rs
+++ b/src/tools/clippy/clippy_lints/src/manual_async_fn.rs
@@ -4,7 +4,7 @@ use rustc_errors::Applicability;
 use rustc_hir::intravisit::FnKind;
 use rustc_hir::{
     Block, Body, Closure, ClosureKind, CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, ExprKind, FnDecl,
-    FnRetTy, GenericArg, GenericBound, ImplItem, Item, ItemKind, LifetimeName, Node, TraitRef, Ty, TyKind,
+    FnRetTy, GenericArg, GenericBound, ImplItem, Item, LifetimeName, Node, TraitRef, Ty, TyKind,
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::declare_lint_pass;
@@ -105,9 +105,7 @@ fn future_trait_ref<'tcx>(
     cx: &LateContext<'tcx>,
     ty: &'tcx Ty<'tcx>,
 ) -> Option<(&'tcx TraitRef<'tcx>, Vec<LifetimeName>)> {
-    if let TyKind::OpaqueDef(item_id, bounds) = ty.kind
-        && let item = cx.tcx.hir().item(item_id)
-        && let ItemKind::OpaqueTy(opaque) = &item.kind
+    if let TyKind::OpaqueDef(opaque, bounds) = ty.kind
         && let Some(trait_ref) = opaque.bounds.iter().find_map(|bound| {
             if let GenericBound::Trait(poly, _) = bound {
                 Some(&poly.trait_ref)
diff --git a/src/tools/clippy/clippy_lints/src/missing_doc.rs b/src/tools/clippy/clippy_lints/src/missing_doc.rs
index 64fc1a8a1a5..007bcebdff6 100644
--- a/src/tools/clippy/clippy_lints/src/missing_doc.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_doc.rs
@@ -193,8 +193,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
             | hir::ItemKind::Trait(..)
             | hir::ItemKind::TraitAlias(..)
             | hir::ItemKind::TyAlias(..)
-            | hir::ItemKind::Union(..)
-            | hir::ItemKind::OpaqueTy(..) => {},
+            | hir::ItemKind::Union(..) => {}
             hir::ItemKind::ExternCrate(..)
             | hir::ItemKind::ForeignMod { .. }
             | hir::ItemKind::GlobalAsm(..)
diff --git a/src/tools/clippy/clippy_lints/src/missing_inline.rs b/src/tools/clippy/clippy_lints/src/missing_inline.rs
index d342be4545c..f95a0f63fab 100644
--- a/src/tools/clippy/clippy_lints/src/missing_inline.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_inline.rs
@@ -130,7 +130,6 @@ impl<'tcx> LateLintPass<'tcx> for MissingInline {
             | hir::ItemKind::GlobalAsm(..)
             | hir::ItemKind::TyAlias(..)
             | hir::ItemKind::Union(..)
-            | hir::ItemKind::OpaqueTy(..)
             | hir::ItemKind::ExternCrate(..)
             | hir::ItemKind::ForeignMod { .. }
             | hir::ItemKind::Impl { .. }
diff --git a/src/tools/clippy/clippy_lints/src/use_self.rs b/src/tools/clippy/clippy_lints/src/use_self.rs
index 08449de79b3..f5cf4a586fd 100644
--- a/src/tools/clippy/clippy_lints/src/use_self.rs
+++ b/src/tools/clippy/clippy_lints/src/use_self.rs
@@ -85,10 +85,6 @@ const SEGMENTS_MSG: &str = "segments should be composed of at least 1 element";
 
 impl<'tcx> LateLintPass<'tcx> for UseSelf {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &Item<'tcx>) {
-        if matches!(item.kind, ItemKind::OpaqueTy(_)) {
-            // skip over `ItemKind::OpaqueTy` in order to lint `foo() -> impl <..>`
-            return;
-        }
         // We push the self types of `impl`s on a stack here. Only the top type on the stack is
         // relevant for linting, since this is the self type of the `impl` we're currently in. To
         // avoid linting on nested items, we push `StackItem::NoCheck` on the stack to signal, that
@@ -130,10 +126,8 @@ impl<'tcx> LateLintPass<'tcx> for UseSelf {
         self.stack.push(stack_item);
     }
 
-    fn check_item_post(&mut self, _: &LateContext<'_>, item: &Item<'_>) {
-        if !matches!(item.kind, ItemKind::OpaqueTy(_)) {
-            self.stack.pop();
-        }
+    fn check_item_post(&mut self, _: &LateContext<'_>, _: &Item<'_>) {
+        self.stack.pop();
     }
 
     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
diff --git a/src/tools/clippy/clippy_utils/src/check_proc_macro.rs b/src/tools/clippy/clippy_utils/src/check_proc_macro.rs
index 9143d292f67..b18997e6ee4 100644
--- a/src/tools/clippy/clippy_utils/src/check_proc_macro.rs
+++ b/src/tools/clippy/clippy_utils/src/check_proc_macro.rs
@@ -220,7 +220,7 @@ fn item_search_pat(item: &Item<'_>) -> (Pat, Pat) {
         ItemKind::Const(..) => (Pat::Str("const"), Pat::Str(";")),
         ItemKind::Fn(sig, ..) => (fn_header_search_pat(sig.header), Pat::Str("")),
         ItemKind::ForeignMod { .. } => (Pat::Str("extern"), Pat::Str("}")),
-        ItemKind::TyAlias(..) | ItemKind::OpaqueTy(_) => (Pat::Str("type"), Pat::Str(";")),
+        ItemKind::TyAlias(..) => (Pat::Str("type"), Pat::Str(";")),
         ItemKind::Enum(..) => (Pat::Str("enum"), Pat::Str("}")),
         ItemKind::Struct(VariantData::Struct { .. }, _) => (Pat::Str("struct"), Pat::Str("}")),
         ItemKind::Struct(..) => (Pat::Str("struct"), Pat::Str(";")),