1 use super::{AnonymousLifetimeMode, LoweringContext, ParamMode};
2 use super::{ImplTraitContext, ImplTraitPosition};
5 use rustc_ast::node_id::NodeMap;
7 use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
9 use rustc_data_structures::fx::FxHashSet;
10 use rustc_errors::struct_span_err;
12 use rustc_hir::def::{DefKind, Res};
13 use rustc_hir::def_id::LocalDefId;
14 use rustc_span::source_map::{respan, DesugaringKind};
15 use rustc_span::symbol::{kw, sym, Ident};
17 use rustc_target::spec::abi;
18 use smallvec::{smallvec, SmallVec};
23 pub(super) struct ItemLowerer<'a, 'lowering, 'hir> {
24 pub(super) lctx: &'a mut LoweringContext<'lowering, 'hir>,
27 impl ItemLowerer<'_, '_, '_> {
28 fn with_trait_impl_ref(&mut self, impl_ref: &Option<TraitRef>, f: impl FnOnce(&mut Self)) {
29 let old = self.lctx.is_in_trait_impl;
30 self.lctx.is_in_trait_impl = impl_ref.is_some();
32 self.lctx.is_in_trait_impl = old;
36 impl<'a> Visitor<'a> for ItemLowerer<'a, '_, '_> {
37 fn visit_item(&mut self, item: &'a Item) {
38 let mut item_hir_id = None;
39 self.lctx.with_hir_id_owner(item.id, |lctx| {
40 lctx.without_in_scope_lifetime_defs(|lctx| {
41 if let Some(hir_item) = lctx.lower_item(item) {
42 let id = lctx.insert_item(hir_item);
43 item_hir_id = Some(id);
48 if let Some(hir_id) = item_hir_id {
49 self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
50 let this = &mut ItemLowerer { lctx: this };
52 ItemKind::Mod(..) => {
53 let def_id = this.lctx.lower_node_id(item.id).expect_owner();
54 let old_current_module =
55 mem::replace(&mut this.lctx.current_module, def_id);
56 visit::walk_item(this, item);
57 this.lctx.current_module = old_current_module;
59 ItemKind::Impl(box ImplKind { ref of_trait, .. }) => {
60 this.with_trait_impl_ref(of_trait, |this| visit::walk_item(this, item));
62 _ => visit::walk_item(this, item),
68 fn visit_fn(&mut self, fk: FnKind<'a>, sp: Span, _: NodeId) {
70 FnKind::Fn(FnCtxt::Foreign, _, sig, _, _) => {
71 self.visit_fn_header(&sig.header);
72 visit::walk_fn_decl(self, &sig.decl);
73 // Don't visit the foreign function body even if it has one, since lowering the
74 // body would have no meaning and will have already been caught as a parse error.
76 _ => visit::walk_fn(self, fk, sp),
80 fn visit_assoc_item(&mut self, item: &'a AssocItem, ctxt: AssocCtxt) {
81 self.lctx.with_hir_id_owner(item.id, |lctx| match ctxt {
83 let hir_item = lctx.lower_trait_item(item);
84 let id = hir_item.trait_item_id();
85 lctx.trait_items.insert(id, hir_item);
86 lctx.modules.entry(lctx.current_module).or_default().trait_items.insert(id);
89 let hir_item = lctx.lower_impl_item(item);
90 let id = hir_item.impl_item_id();
91 lctx.impl_items.insert(id, hir_item);
92 lctx.modules.entry(lctx.current_module).or_default().impl_items.insert(id);
96 visit::walk_assoc_item(self, item, ctxt);
99 fn visit_foreign_item(&mut self, item: &'a ForeignItem) {
100 self.lctx.allocate_hir_id_counter(item.id);
101 self.lctx.with_hir_id_owner(item.id, |lctx| {
102 let hir_item = lctx.lower_foreign_item(item);
103 let id = hir_item.foreign_item_id();
104 lctx.foreign_items.insert(id, hir_item);
105 lctx.modules.entry(lctx.current_module).or_default().foreign_items.insert(id);
108 visit::walk_foreign_item(self, item);
112 impl<'hir> LoweringContext<'_, 'hir> {
113 // Same as the method above, but accepts `hir::GenericParam`s
114 // instead of `ast::GenericParam`s.
115 // This should only be used with generics that have already had their
116 // in-band lifetimes added. In practice, this means that this function is
117 // only used when lowering a child item of a trait or impl.
118 fn with_parent_item_lifetime_defs<T>(
120 parent_hir_id: hir::ItemId,
121 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
123 let old_len = self.in_scope_lifetimes.len();
125 let parent_generics = match self.items.get(&parent_hir_id).unwrap().kind {
126 hir::ItemKind::Impl(hir::Impl { ref generics, .. })
127 | hir::ItemKind::Trait(_, _, ref generics, ..) => generics.params,
130 let lt_def_names = parent_generics.iter().filter_map(|param| match param.kind {
131 hir::GenericParamKind::Lifetime { .. } => Some(param.name.normalize_to_macros_2_0()),
134 self.in_scope_lifetimes.extend(lt_def_names);
138 self.in_scope_lifetimes.truncate(old_len);
142 // Clears (and restores) the `in_scope_lifetimes` field. Used when
143 // visiting nested items, which never inherit in-scope lifetimes
144 // from their surrounding environment.
145 fn without_in_scope_lifetime_defs<T>(
147 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
149 let old_in_scope_lifetimes = mem::replace(&mut self.in_scope_lifetimes, vec![]);
151 // this vector is only used when walking over impl headers,
152 // input types, and the like, and should not be non-empty in
154 assert!(self.lifetimes_to_define.is_empty());
158 assert!(self.in_scope_lifetimes.is_empty());
159 self.in_scope_lifetimes = old_in_scope_lifetimes;
164 pub(super) fn lower_mod(&mut self, items: &[P<Item>], inner: Span) -> hir::Mod<'hir> {
167 item_ids: self.arena.alloc_from_iter(items.iter().flat_map(|x| self.lower_item_id(x))),
171 pub(super) fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
172 let node_ids = match i.kind {
173 ItemKind::Use(ref use_tree) => {
174 let mut vec = smallvec![i.id];
175 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
178 ItemKind::MacroDef(..) => SmallVec::new(),
179 ItemKind::Fn(..) | ItemKind::Impl(box ImplKind { of_trait: None, .. }) => {
182 _ => smallvec![i.id],
187 .map(|node_id| hir::ItemId {
188 def_id: self.allocate_hir_id_counter(node_id).expect_owner(),
193 fn lower_item_id_use_tree(
197 vec: &mut SmallVec<[NodeId; 1]>,
200 UseTreeKind::Nested(ref nested_vec) => {
201 for &(ref nested, id) in nested_vec {
203 self.lower_item_id_use_tree(nested, id, vec);
206 UseTreeKind::Glob => {}
207 UseTreeKind::Simple(_, id1, id2) => {
209 self.expect_full_res_from_use(base_id).skip(1).zip([id1, id2].iter())
217 pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item<'hir>> {
218 let mut ident = i.ident;
219 let mut vis = self.lower_visibility(&i.vis, None);
221 if let ItemKind::MacroDef(MacroDef { ref body, macro_rules }) = i.kind {
222 if !macro_rules || self.sess.contains_name(&i.attrs, sym::macro_export) {
223 let hir_id = self.lower_node_id(i.id);
224 self.lower_attrs(hir_id, &i.attrs);
225 let body = P(self.lower_mac_args(body));
226 self.exported_macros.push(hir::MacroDef {
229 def_id: hir_id.expect_owner(),
231 ast: MacroDef { body, macro_rules },
234 for a in i.attrs.iter() {
235 let a = self.lower_attr(a);
236 self.non_exported_macro_attrs.push(a);
242 let hir_id = self.lower_node_id(i.id);
243 let attrs = self.lower_attrs(hir_id, &i.attrs);
244 let kind = self.lower_item_kind(i.span, i.id, hir_id, &mut ident, attrs, &mut vis, &i.kind);
245 Some(hir::Item { def_id: hir_id.expect_owner(), ident, kind, vis, span: i.span })
254 attrs: Option<&'hir [Attribute]>,
255 vis: &mut hir::Visibility<'hir>,
257 ) -> hir::ItemKind<'hir> {
259 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
260 ItemKind::Use(ref use_tree) => {
261 // Start with an empty prefix.
262 let prefix = Path { segments: vec![], span: use_tree.span, tokens: None };
264 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
266 ItemKind::Static(ref t, m, ref e) => {
267 let (ty, body_id) = self.lower_const_item(t, span, e.as_deref());
268 hir::ItemKind::Static(ty, m, body_id)
270 ItemKind::Const(_, ref t, ref e) => {
271 let (ty, body_id) = self.lower_const_item(t, span, e.as_deref());
272 hir::ItemKind::Const(ty, body_id)
274 ItemKind::Fn(box FnKind(
276 FnSig { ref decl, header, span: fn_sig_span },
280 let fn_def_id = self.resolver.local_def_id(id);
281 self.with_new_scopes(|this| {
282 this.current_item = Some(ident.span);
284 // Note: we don't need to change the return type from `T` to
285 // `impl Future<Output = T>` here because lower_body
286 // only cares about the input argument patterns in the function
287 // declaration (decl), not the return types.
288 let asyncness = header.asyncness;
290 this.lower_maybe_async_body(span, &decl, asyncness, body.as_deref());
292 let (generics, decl) = this.add_in_band_defs(
295 AnonymousLifetimeMode::PassThrough,
297 let ret_id = asyncness.opt_return_id();
300 Some((fn_def_id.to_def_id(), idty)),
306 let sig = hir::FnSig {
308 header: this.lower_fn_header(header, fn_sig_span, id),
311 hir::ItemKind::Fn(sig, generics, body_id)
314 ItemKind::Mod(_, ref mod_kind) => match mod_kind {
315 ModKind::Loaded(items, _, inner_span) => {
316 hir::ItemKind::Mod(self.lower_mod(items, *inner_span))
318 ModKind::Unloaded => panic!("`mod` items should have been loaded by now"),
320 ItemKind::ForeignMod(ref fm) => {
321 if fm.abi.is_none() {
322 self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
324 hir::ItemKind::ForeignMod {
325 abi: fm.abi.map_or(abi::Abi::C { unwind: false }, |abi| self.lower_abi(abi)),
328 .alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item_ref(x))),
331 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
332 ItemKind::TyAlias(box TyAliasKind(_, ref gen, _, Some(ref ty))) => {
335 // type Foo = impl Trait
340 // opaque type Foo1: Trait
341 let ty = self.lower_ty(
343 ImplTraitContext::OtherOpaqueTy {
344 capturable_lifetimes: &mut FxHashSet::default(),
345 origin: hir::OpaqueTyOrigin::TyAlias,
348 let generics = self.lower_generics(gen, ImplTraitContext::disallowed());
349 hir::ItemKind::TyAlias(ty, generics)
351 ItemKind::TyAlias(box TyAliasKind(_, ref generics, _, None)) => {
352 let ty = self.arena.alloc(self.ty(span, hir::TyKind::Err));
353 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
354 hir::ItemKind::TyAlias(ty, generics)
356 ItemKind::Enum(ref enum_definition, ref generics) => hir::ItemKind::Enum(
358 variants: self.arena.alloc_from_iter(
359 enum_definition.variants.iter().map(|x| self.lower_variant(x)),
362 self.lower_generics(generics, ImplTraitContext::disallowed()),
364 ItemKind::Struct(ref struct_def, ref generics) => {
365 let struct_def = self.lower_variant_data(hir_id, struct_def);
366 hir::ItemKind::Struct(
368 self.lower_generics(generics, ImplTraitContext::disallowed()),
371 ItemKind::Union(ref vdata, ref generics) => {
372 let vdata = self.lower_variant_data(hir_id, vdata);
373 hir::ItemKind::Union(
375 self.lower_generics(generics, ImplTraitContext::disallowed()),
378 ItemKind::Impl(box ImplKind {
383 generics: ref ast_generics,
384 of_trait: ref trait_ref,
386 items: ref impl_items,
388 // Lower the "impl header" first. This ordering is important
389 // for in-band lifetimes! Consider `'a` here:
391 // impl Foo<'a> for u32 {
392 // fn method(&'a self) { .. }
395 // Because we start by lowering the `Foo<'a> for u32`
396 // part, we will add `'a` to the list of generics on
397 // the impl. When we then encounter it later in the
398 // method, it will not be considered an in-band
399 // lifetime to be added, but rather a reference to a
401 let lowered_trait_def_id = self.lower_node_id(id).expect_owner();
402 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
404 lowered_trait_def_id,
405 AnonymousLifetimeMode::CreateParameter,
407 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
408 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
411 if let Some(ref trait_ref) = trait_ref {
412 if let Res::Def(DefKind::Trait, def_id) = trait_ref.path.res {
416 .push(lowered_trait_def_id);
420 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
422 (trait_ref, lowered_ty)
427 self.with_in_scope_lifetime_defs(&ast_generics.params, |this| {
428 this.arena.alloc_from_iter(
429 impl_items.iter().map(|item| this.lower_impl_item_ref(item)),
433 // `defaultness.has_value()` is never called for an `impl`, always `true` in order
434 // to not cause an assertion failure inside the `lower_defaultness` function.
436 let (defaultness, defaultness_span) = self.lower_defaultness(defaultness, has_val);
437 hir::ItemKind::Impl(hir::Impl {
438 unsafety: self.lower_unsafety(unsafety),
442 constness: self.lower_constness(constness),
446 items: new_impl_items,
449 ItemKind::Trait(box TraitKind(
456 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
459 .alloc_from_iter(items.iter().map(|item| self.lower_trait_item_ref(item)));
460 hir::ItemKind::Trait(
462 self.lower_unsafety(unsafety),
463 self.lower_generics(generics, ImplTraitContext::disallowed()),
468 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
469 self.lower_generics(generics, ImplTraitContext::disallowed()),
470 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
472 ItemKind::MacroDef(..) | ItemKind::MacCall(..) => {
473 panic!("`TyMac` should have been expanded by now")
483 ) -> (&'hir hir::Ty<'hir>, hir::BodyId) {
484 let mut capturable_lifetimes;
485 let itctx = if self.sess.features_untracked().impl_trait_in_bindings {
486 capturable_lifetimes = FxHashSet::default();
487 ImplTraitContext::OtherOpaqueTy {
488 capturable_lifetimes: &mut capturable_lifetimes,
489 origin: hir::OpaqueTyOrigin::Misc,
492 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
494 let ty = self.lower_ty(ty, itctx);
495 (ty, self.lower_const_body(span, body))
503 vis: &mut hir::Visibility<'hir>,
505 attrs: Option<&'hir [Attribute]>,
506 ) -> hir::ItemKind<'hir> {
507 debug!("lower_use_tree(tree={:?})", tree);
508 debug!("lower_use_tree: vis = {:?}", vis);
510 let path = &tree.prefix;
511 let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect();
514 UseTreeKind::Simple(rename, id1, id2) => {
515 *ident = tree.ident();
517 // First, apply the prefix to the path.
518 let mut path = Path { segments, span: path.span, tokens: None };
520 // Correctly resolve `self` imports.
521 if path.segments.len() > 1
522 && path.segments.last().unwrap().ident.name == kw::SelfLower
524 let _ = path.segments.pop();
525 if rename.is_none() {
526 *ident = path.segments.last().unwrap().ident;
530 let mut resolutions = self.expect_full_res_from_use(id);
531 // We want to return *something* from this function, so hold onto the first item
533 let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
535 // Here, we are looping over namespaces, if they exist for the definition
536 // being imported. We only handle type and value namespaces because we
537 // won't be dealing with macros in the rest of the compiler.
538 // Essentially a single `use` which imports two names is desugared into
540 for (res, &new_node_id) in resolutions.zip([id1, id2].iter()) {
542 let mut path = path.clone();
543 for seg in &mut path.segments {
544 seg.id = self.resolver.next_node_id();
546 let span = path.span;
548 self.with_hir_id_owner(new_node_id, |this| {
549 let new_id = this.lower_node_id(new_node_id);
550 let res = this.lower_res(res);
551 let path = this.lower_path_extra(res, &path, ParamMode::Explicit, None);
552 let kind = hir::ItemKind::Use(path, hir::UseKind::Single);
553 let vis = this.rebuild_vis(&vis);
554 if let Some(attrs) = attrs {
555 this.attrs.insert(new_id, attrs);
558 this.insert_item(hir::Item {
559 def_id: new_id.expect_owner(),
568 let path = self.lower_path_extra(ret_res, &path, ParamMode::Explicit, None);
569 hir::ItemKind::Use(path, hir::UseKind::Single)
571 UseTreeKind::Glob => {
572 let path = self.lower_path(
574 &Path { segments, span: path.span, tokens: None },
577 hir::ItemKind::Use(path, hir::UseKind::Glob)
579 UseTreeKind::Nested(ref trees) => {
580 // Nested imports are desugared into simple imports.
581 // So, if we start with
584 // pub(x) use foo::{a, b};
587 // we will create three items:
590 // pub(x) use foo::a;
591 // pub(x) use foo::b;
592 // pub(x) use foo::{}; // <-- this is called the `ListStem`
595 // The first two are produced by recursively invoking
596 // `lower_use_tree` (and indeed there may be things
597 // like `use foo::{a::{b, c}}` and so forth). They
598 // wind up being directly added to
599 // `self.items`. However, the structure of this
600 // function also requires us to return one item, and
601 // for that we return the `{}` import (called the
604 let prefix = Path { segments, span: prefix.span.to(path.span), tokens: None };
606 // Add all the nested `PathListItem`s to the HIR.
607 for &(ref use_tree, id) in trees {
608 let new_hir_id = self.lower_node_id(id);
610 let mut prefix = prefix.clone();
612 // Give the segments new node-ids since they are being cloned.
613 for seg in &mut prefix.segments {
614 seg.id = self.resolver.next_node_id();
617 // Each `use` import is an item and thus are owners of the
618 // names in the path. Up to this point the nested import is
619 // the current owner, since we want each desugared import to
620 // own its own names, we have to adjust the owner before
621 // lowering the rest of the import.
622 self.with_hir_id_owner(id, |this| {
623 let mut vis = this.rebuild_vis(&vis);
624 let mut ident = *ident;
627 this.lower_use_tree(use_tree, &prefix, id, &mut vis, &mut ident, attrs);
628 if let Some(attrs) = attrs {
629 this.attrs.insert(new_hir_id, attrs);
632 this.insert_item(hir::Item {
633 def_id: new_hir_id.expect_owner(),
642 // Subtle and a bit hacky: we lower the privacy level
643 // of the list stem to "private" most of the time, but
644 // not for "restricted" paths. The key thing is that
645 // we don't want it to stay as `pub` (with no caveats)
646 // because that affects rustdoc and also the lints
647 // about `pub` items. But we can't *always* make it
648 // private -- particularly not for restricted paths --
649 // because it contains node-ids that would then be
650 // unused, failing the check that HirIds are "densely
653 hir::VisibilityKind::Public
654 | hir::VisibilityKind::Crate(_)
655 | hir::VisibilityKind::Inherited => {
656 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
658 hir::VisibilityKind::Restricted { .. } => {
659 // Do nothing here, as described in the comment on the match.
663 let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
664 let res = self.lower_res(res);
665 let path = self.lower_path_extra(res, &prefix, ParamMode::Explicit, None);
666 hir::ItemKind::Use(path, hir::UseKind::ListStem)
671 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
672 /// many times in the HIR tree; for each occurrence, we need to assign distinct
673 /// `NodeId`s. (See, e.g., #56128.)
674 fn rebuild_use_path(&mut self, path: &hir::Path<'hir>) -> &'hir hir::Path<'hir> {
675 debug!("rebuild_use_path(path = {:?})", path);
677 self.arena.alloc_from_iter(path.segments.iter().map(|seg| hir::PathSegment {
679 hir_id: seg.hir_id.map(|_| self.next_id()),
682 infer_args: seg.infer_args,
684 self.arena.alloc(hir::Path { span: path.span, res: path.res, segments })
687 fn rebuild_vis(&mut self, vis: &hir::Visibility<'hir>) -> hir::Visibility<'hir> {
688 let vis_kind = match vis.node {
689 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
690 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
691 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
692 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
693 hir::VisibilityKind::Restricted {
694 path: self.rebuild_use_path(path),
695 hir_id: self.next_id(),
699 respan(vis.span, vis_kind)
702 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem<'hir> {
703 let hir_id = self.lower_node_id(i.id);
704 let def_id = hir_id.expect_owner();
705 self.lower_attrs(hir_id, &i.attrs);
710 ForeignItemKind::Fn(box FnKind(_, ref sig, ref generics, _)) => {
711 let fdec = &sig.decl;
712 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
715 AnonymousLifetimeMode::PassThrough,
718 // Disallow `impl Trait` in foreign items.
719 this.lower_fn_decl(fdec, None, false, None),
720 this.lower_fn_params_to_names(fdec),
725 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
727 ForeignItemKind::Static(ref t, m, _) => {
728 let ty = self.lower_ty(t, ImplTraitContext::disallowed());
729 hir::ForeignItemKind::Static(ty, m)
731 ForeignItemKind::TyAlias(..) => hir::ForeignItemKind::Type,
732 ForeignItemKind::MacCall(_) => panic!("macro shouldn't exist here"),
734 vis: self.lower_visibility(&i.vis, None),
739 fn lower_foreign_item_ref(&mut self, i: &ForeignItem) -> hir::ForeignItemRef<'hir> {
740 hir::ForeignItemRef {
741 id: hir::ForeignItemId { def_id: self.lower_node_id(i.id).expect_owner() },
744 vis: self.lower_visibility(&i.vis, Some(i.id)),
748 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> &'hir hir::GlobalAsm {
749 self.arena.alloc(hir::GlobalAsm { asm: ga.asm })
752 fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> {
753 let id = self.lower_node_id(v.id);
754 self.lower_attrs(id, &v.attrs);
757 data: self.lower_variant_data(id, &v.data),
758 disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
764 fn lower_variant_data(
766 parent_id: hir::HirId,
768 ) -> hir::VariantData<'hir> {
770 VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
772 .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_field_def(f))),
775 VariantData::Tuple(ref fields, id) => {
776 let ctor_id = self.lower_node_id(id);
777 self.alias_attrs(ctor_id, parent_id);
778 hir::VariantData::Tuple(
779 self.arena.alloc_from_iter(
780 fields.iter().enumerate().map(|f| self.lower_field_def(f)),
785 VariantData::Unit(id) => {
786 let ctor_id = self.lower_node_id(id);
787 self.alias_attrs(ctor_id, parent_id);
788 hir::VariantData::Unit(ctor_id)
793 fn lower_field_def(&mut self, (index, f): (usize, &FieldDef)) -> hir::FieldDef<'hir> {
794 let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
795 let t = self.lower_path_ty(
799 ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
800 ImplTraitContext::disallowed(),
804 self.lower_ty(&f.ty, ImplTraitContext::disallowed())
806 let hir_id = self.lower_node_id(f.id);
807 self.lower_attrs(hir_id, &f.attrs);
811 ident: match f.ident {
812 Some(ident) => ident,
813 // FIXME(jseyfried): positional field hygiene.
814 None => Ident::new(sym::integer(index), f.span),
816 vis: self.lower_visibility(&f.vis, None),
821 fn lower_trait_item(&mut self, i: &AssocItem) -> hir::TraitItem<'hir> {
822 let hir_id = self.lower_node_id(i.id);
823 let trait_item_def_id = hir_id.expect_owner();
825 let (generics, kind) = match i.kind {
826 AssocItemKind::Const(_, ref ty, ref default) => {
827 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
828 let body = default.as_ref().map(|x| self.lower_const_body(i.span, Some(x)));
829 (hir::Generics::empty(), hir::TraitItemKind::Const(ty, body))
831 AssocItemKind::Fn(box FnKind(_, ref sig, ref generics, None)) => {
832 let names = self.lower_fn_params_to_names(&sig.decl);
833 let (generics, sig) =
834 self.lower_method_sig(generics, sig, trait_item_def_id, false, None, i.id);
835 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)))
837 AssocItemKind::Fn(box FnKind(_, ref sig, ref generics, Some(ref body))) => {
838 let body_id = self.lower_fn_body_block(i.span, &sig.decl, Some(body));
839 let (generics, sig) =
840 self.lower_method_sig(generics, sig, trait_item_def_id, false, None, i.id);
841 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)))
843 AssocItemKind::TyAlias(box TyAliasKind(_, ref generics, ref bounds, ref default)) => {
844 let ty = default.as_ref().map(|x| self.lower_ty(x, ImplTraitContext::disallowed()));
845 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
846 let kind = hir::TraitItemKind::Type(
847 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
853 AssocItemKind::MacCall(..) => panic!("macro item shouldn't exist at this point"),
856 self.lower_attrs(hir_id, &i.attrs);
857 hir::TraitItem { def_id: trait_item_def_id, ident: i.ident, generics, kind, span: i.span }
860 fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef {
861 let (kind, has_default) = match &i.kind {
862 AssocItemKind::Const(_, _, default) => (hir::AssocItemKind::Const, default.is_some()),
863 AssocItemKind::TyAlias(box TyAliasKind(_, _, _, default)) => {
864 (hir::AssocItemKind::Type, default.is_some())
866 AssocItemKind::Fn(box FnKind(_, sig, _, default)) => {
867 (hir::AssocItemKind::Fn { has_self: sig.decl.has_self() }, default.is_some())
869 AssocItemKind::MacCall(..) => unimplemented!(),
871 let id = hir::TraitItemId { def_id: self.lower_node_id(i.id).expect_owner() };
872 let defaultness = hir::Defaultness::Default { has_value: has_default };
873 hir::TraitItemRef { id, ident: i.ident, span: i.span, defaultness, kind }
876 /// Construct `ExprKind::Err` for the given `span`.
877 crate fn expr_err(&mut self, span: Span) -> hir::Expr<'hir> {
878 self.expr(span, hir::ExprKind::Err, AttrVec::new())
881 fn lower_impl_item(&mut self, i: &AssocItem) -> hir::ImplItem<'hir> {
882 let impl_item_def_id = self.resolver.local_def_id(i.id);
884 let (generics, kind) = match &i.kind {
885 AssocItemKind::Const(_, ty, expr) => {
886 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
888 hir::Generics::empty(),
889 hir::ImplItemKind::Const(ty, self.lower_const_body(i.span, expr.as_deref())),
892 AssocItemKind::Fn(box FnKind(_, sig, generics, body)) => {
893 self.current_item = Some(i.span);
894 let asyncness = sig.header.asyncness;
896 self.lower_maybe_async_body(i.span, &sig.decl, asyncness, body.as_deref());
897 let impl_trait_return_allow = !self.is_in_trait_impl;
898 let (generics, sig) = self.lower_method_sig(
902 impl_trait_return_allow,
903 asyncness.opt_return_id(),
907 (generics, hir::ImplItemKind::Fn(sig, body_id))
909 AssocItemKind::TyAlias(box TyAliasKind(_, generics, _, ty)) => {
910 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
911 let kind = match ty {
913 let ty = self.arena.alloc(self.ty(i.span, hir::TyKind::Err));
914 hir::ImplItemKind::TyAlias(ty)
917 let ty = self.lower_ty(
919 ImplTraitContext::OtherOpaqueTy {
920 capturable_lifetimes: &mut FxHashSet::default(),
921 origin: hir::OpaqueTyOrigin::TyAlias,
924 hir::ImplItemKind::TyAlias(ty)
929 AssocItemKind::MacCall(..) => panic!("`TyMac` should have been expanded by now"),
932 // Since `default impl` is not yet implemented, this is always true in impls.
933 let has_value = true;
934 let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
935 let hir_id = self.lower_node_id(i.id);
936 self.lower_attrs(hir_id, &i.attrs);
938 def_id: hir_id.expect_owner(),
941 vis: self.lower_visibility(&i.vis, None),
948 fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef<'hir> {
949 // Since `default impl` is not yet implemented, this is always true in impls.
950 let has_value = true;
951 let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
953 id: hir::ImplItemId { def_id: self.lower_node_id(i.id).expect_owner() },
956 vis: self.lower_visibility(&i.vis, Some(i.id)),
958 kind: match &i.kind {
959 AssocItemKind::Const(..) => hir::AssocItemKind::Const,
960 AssocItemKind::TyAlias(..) => hir::AssocItemKind::Type,
961 AssocItemKind::Fn(box FnKind(_, sig, ..)) => {
962 hir::AssocItemKind::Fn { has_self: sig.decl.has_self() }
964 AssocItemKind::MacCall(..) => unimplemented!(),
969 /// If an `explicit_owner` is given, this method allocates the `HirId` in
970 /// the address space of that item instead of the item currently being
971 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
972 /// lower a `Visibility` value although we haven't lowered the owning
973 /// `ImplItem` in question yet.
977 explicit_owner: Option<NodeId>,
978 ) -> hir::Visibility<'hir> {
979 let node = match v.kind {
980 VisibilityKind::Public => hir::VisibilityKind::Public,
981 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
982 VisibilityKind::Restricted { ref path, id } => {
983 debug!("lower_visibility: restricted path id = {:?}", id);
984 let lowered_id = if let Some(owner) = explicit_owner {
985 self.lower_node_id_with_owner(id, owner)
987 self.lower_node_id(id)
989 let res = self.expect_full_res(id);
990 let res = self.lower_res(res);
991 hir::VisibilityKind::Restricted {
992 path: self.lower_path_extra(res, path, ParamMode::Explicit, explicit_owner),
996 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
1001 fn lower_defaultness(
1005 ) -> (hir::Defaultness, Option<Span>) {
1007 Defaultness::Default(sp) => (hir::Defaultness::Default { has_value }, Some(sp)),
1008 Defaultness::Final => {
1010 (hir::Defaultness::Final, None)
1017 params: &'hir [hir::Param<'hir>],
1018 value: hir::Expr<'hir>,
1020 let body = hir::Body { generator_kind: self.generator_kind, params, value };
1022 self.bodies.insert(id, body);
1026 pub(super) fn lower_body(
1028 f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>),
1030 let prev_gen_kind = self.generator_kind.take();
1031 let task_context = self.task_context.take();
1032 let (parameters, result) = f(self);
1033 let body_id = self.record_body(parameters, result);
1034 self.task_context = task_context;
1035 self.generator_kind = prev_gen_kind;
1039 fn lower_param(&mut self, param: &Param) -> hir::Param<'hir> {
1040 let hir_id = self.lower_node_id(param.id);
1041 self.lower_attrs(hir_id, ¶m.attrs);
1044 pat: self.lower_pat(¶m.pat),
1045 ty_span: param.ty.span,
1050 pub(super) fn lower_fn_body(
1053 body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
1055 self.lower_body(|this| {
1057 this.arena.alloc_from_iter(decl.inputs.iter().map(|x| this.lower_param(x))),
1063 fn lower_fn_body_block(
1067 body: Option<&Block>,
1069 self.lower_fn_body(decl, |this| this.lower_block_expr_opt(span, body))
1072 fn lower_block_expr_opt(&mut self, span: Span, block: Option<&Block>) -> hir::Expr<'hir> {
1074 Some(block) => self.lower_block_expr(block),
1075 None => self.expr_err(span),
1079 pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
1080 self.lower_body(|this| {
1084 Some(expr) => this.lower_expr_mut(expr),
1085 None => this.expr_err(span),
1091 fn lower_maybe_async_body(
1096 body: Option<&Block>,
1098 let closure_id = match asyncness {
1099 Async::Yes { closure_id, .. } => closure_id,
1100 Async::No => return self.lower_fn_body_block(span, decl, body),
1103 self.lower_body(|this| {
1104 let mut parameters: Vec<hir::Param<'_>> = Vec::new();
1105 let mut statements: Vec<hir::Stmt<'_>> = Vec::new();
1107 // Async function parameters are lowered into the closure body so that they are
1108 // captured and so that the drop order matches the equivalent non-async functions.
1112 // async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
1118 // fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
1120 // let __arg2 = __arg2;
1121 // let <pattern> = __arg2;
1122 // let __arg1 = __arg1;
1123 // let <pattern> = __arg1;
1124 // let __arg0 = __arg0;
1125 // let <pattern> = __arg0;
1126 // drop-temps { <body> } // see comments later in fn for details
1130 // If `<pattern>` is a simple ident, then it is lowered to a single
1131 // `let <pattern> = <pattern>;` statement as an optimization.
1133 // Note that the body is embedded in `drop-temps`; an
1134 // equivalent desugaring would be `return { <body>
1135 // };`. The key point is that we wish to drop all the
1136 // let-bound variables and temporaries created in the body
1137 // (and its tail expression!) before we drop the
1138 // parameters (c.f. rust-lang/rust#64512).
1139 for (index, parameter) in decl.inputs.iter().enumerate() {
1140 let parameter = this.lower_param(parameter);
1141 let span = parameter.pat.span;
1143 // Check if this is a binding pattern, if so, we can optimize and avoid adding a
1144 // `let <pat> = __argN;` statement. In this case, we do not rename the parameter.
1145 let (ident, is_simple_parameter) = match parameter.pat.kind {
1146 hir::PatKind::Binding(
1147 hir::BindingAnnotation::Unannotated | hir::BindingAnnotation::Mutable,
1152 // For `ref mut` or wildcard arguments, we can't reuse the binding, but
1153 // we can keep the same name for the parameter.
1154 // This lets rustdoc render it correctly in documentation.
1155 hir::PatKind::Binding(_, _, ident, _) => (ident, false),
1156 hir::PatKind::Wild => {
1157 (Ident::with_dummy_span(rustc_span::symbol::kw::Underscore), false)
1160 // Replace the ident for bindings that aren't simple.
1161 let name = format!("__arg{}", index);
1162 let ident = Ident::from_str(&name);
1168 let desugared_span = this.mark_span_with_reason(DesugaringKind::Async, span, None);
1170 // Construct a parameter representing `__argN: <ty>` to replace the parameter of the
1173 // If this is the simple case, this parameter will end up being the same as the
1174 // original parameter, but with a different pattern id.
1175 let stmt_attrs = this.attrs.get(¶meter.hir_id).copied();
1176 let (new_parameter_pat, new_parameter_id) = this.pat_ident(desugared_span, ident);
1177 let new_parameter = hir::Param {
1178 hir_id: parameter.hir_id,
1179 pat: new_parameter_pat,
1180 ty_span: parameter.ty_span,
1181 span: parameter.span,
1184 if is_simple_parameter {
1185 // If this is the simple case, then we only insert one statement that is
1186 // `let <pat> = <pat>;`. We re-use the original argument's pattern so that
1187 // `HirId`s are densely assigned.
1188 let expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1189 let stmt = this.stmt_let_pat(
1194 hir::LocalSource::AsyncFn,
1196 statements.push(stmt);
1198 // If this is not the simple case, then we construct two statements:
1201 // let __argN = __argN;
1202 // let <pat> = __argN;
1205 // The first statement moves the parameter into the closure and thus ensures
1206 // that the drop order is correct.
1208 // The second statement creates the bindings that the user wrote.
1210 // Construct the `let mut __argN = __argN;` statement. It must be a mut binding
1211 // because the user may have specified a `ref mut` binding in the next
1213 let (move_pat, move_id) = this.pat_ident_binding_mode(
1216 hir::BindingAnnotation::Mutable,
1218 let move_expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1219 let move_stmt = this.stmt_let_pat(
1224 hir::LocalSource::AsyncFn,
1227 // Construct the `let <pat> = __argN;` statement. We re-use the original
1228 // parameter's pattern so that `HirId`s are densely assigned.
1229 let pattern_expr = this.expr_ident(desugared_span, ident, move_id);
1230 let pattern_stmt = this.stmt_let_pat(
1235 hir::LocalSource::AsyncFn,
1238 statements.push(move_stmt);
1239 statements.push(pattern_stmt);
1242 parameters.push(new_parameter);
1245 let body_span = body.map_or(span, |b| b.span);
1246 let async_expr = this.make_async_expr(
1251 hir::AsyncGeneratorKind::Fn,
1253 // Create a block from the user's function body:
1254 let user_body = this.lower_block_expr_opt(body_span, body);
1256 // Transform into `drop-temps { <user-body> }`, an expression:
1257 let desugared_span =
1258 this.mark_span_with_reason(DesugaringKind::Async, user_body.span, None);
1259 let user_body = this.expr_drop_temps(
1261 this.arena.alloc(user_body),
1265 // As noted above, create the final block like
1269 // let $param_pattern = $raw_param;
1271 // drop-temps { <user-body> }
1274 let body = this.block_all(
1276 this.arena.alloc_from_iter(statements),
1280 this.expr_block(body, AttrVec::new())
1285 this.arena.alloc_from_iter(parameters),
1286 this.expr(body_span, async_expr, AttrVec::new()),
1291 fn lower_method_sig(
1293 generics: &Generics,
1295 fn_def_id: LocalDefId,
1296 impl_trait_return_allow: bool,
1297 is_async: Option<NodeId>,
1299 ) -> (hir::Generics<'hir>, hir::FnSig<'hir>) {
1300 let header = self.lower_fn_header(sig.header, sig.span, id);
1301 let (generics, decl) = self.add_in_band_defs(
1304 AnonymousLifetimeMode::PassThrough,
1308 Some((fn_def_id.to_def_id(), idty)),
1309 impl_trait_return_allow,
1314 (generics, hir::FnSig { header, decl, span: sig.span })
1317 fn lower_fn_header(&mut self, h: FnHeader, span: Span, id: NodeId) -> hir::FnHeader {
1319 unsafety: self.lower_unsafety(h.unsafety),
1320 asyncness: self.lower_asyncness(h.asyncness),
1321 constness: self.lower_constness(h.constness),
1322 abi: self.lower_extern(h.ext, span, id),
1326 pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
1327 abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
1328 self.error_on_invalid_abi(abi);
1333 pub(super) fn lower_extern(&mut self, ext: Extern, span: Span, id: NodeId) -> abi::Abi {
1335 Extern::None => abi::Abi::Rust,
1336 Extern::Implicit => {
1337 self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
1338 abi::Abi::C { unwind: false }
1340 Extern::Explicit(abi) => self.lower_abi(abi),
1344 fn error_on_invalid_abi(&self, abi: StrLit) {
1345 struct_span_err!(self.sess, abi.span, E0703, "invalid ABI: found `{}`", abi.symbol)
1346 .span_label(abi.span, "invalid ABI")
1347 .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
1351 fn lower_asyncness(&mut self, a: Async) -> hir::IsAsync {
1353 Async::Yes { .. } => hir::IsAsync::Async,
1354 Async::No => hir::IsAsync::NotAsync,
1358 fn lower_constness(&mut self, c: Const) -> hir::Constness {
1360 Const::Yes(_) => hir::Constness::Const,
1361 Const::No => hir::Constness::NotConst,
1365 pub(super) fn lower_unsafety(&mut self, u: Unsafe) -> hir::Unsafety {
1367 Unsafe::Yes(_) => hir::Unsafety::Unsafe,
1368 Unsafe::No => hir::Unsafety::Normal,
1372 pub(super) fn lower_generics_mut(
1374 generics: &Generics,
1375 itctx: ImplTraitContext<'_, 'hir>,
1376 ) -> GenericsCtor<'hir> {
1377 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
1378 // FIXME: this could probably be done with less rightward drift. It also looks like two
1379 // control paths where `report_error` is called are the only paths that advance to after the
1380 // match statement, so the error reporting could probably just be moved there.
1381 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
1382 for pred in &generics.where_clause.predicates {
1383 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
1384 'next_bound: for bound in &bound_pred.bounds {
1385 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
1386 let report_error = |this: &mut Self| {
1387 this.diagnostic().span_err(
1388 bound_pred.bounded_ty.span,
1389 "`?Trait` bounds are only permitted at the \
1390 point where a type parameter is declared",
1393 // Check if the where clause type is a plain type parameter.
1394 match bound_pred.bounded_ty.kind {
1395 TyKind::Path(None, ref path)
1396 if path.segments.len() == 1
1397 && bound_pred.bound_generic_params.is_empty() =>
1399 if let Some(Res::Def(DefKind::TyParam, def_id)) = self
1401 .get_partial_res(bound_pred.bounded_ty.id)
1402 .map(|d| d.base_res())
1404 if let Some(def_id) = def_id.as_local() {
1405 for param in &generics.params {
1406 if let GenericParamKind::Type { .. } = param.kind {
1407 if def_id == self.resolver.local_def_id(param.id) {
1411 .push(bound.clone());
1412 continue 'next_bound;
1420 _ => report_error(self),
1428 params: self.lower_generic_params_mut(&generics.params, &add_bounds, itctx).collect(),
1429 where_clause: self.lower_where_clause(&generics.where_clause),
1430 span: generics.span,
1434 pub(super) fn lower_generics(
1436 generics: &Generics,
1437 itctx: ImplTraitContext<'_, 'hir>,
1438 ) -> hir::Generics<'hir> {
1439 let generics_ctor = self.lower_generics_mut(generics, itctx);
1440 generics_ctor.into_generics(self.arena)
1443 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause<'hir> {
1444 self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
1446 predicates: this.arena.alloc_from_iter(
1447 wc.predicates.iter().map(|predicate| this.lower_where_predicate(predicate)),
1454 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> {
1456 WherePredicate::BoundPredicate(WhereBoundPredicate {
1457 ref bound_generic_params,
1462 self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
1463 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
1464 bound_generic_params: this.lower_generic_params(
1465 bound_generic_params,
1466 &NodeMap::default(),
1467 ImplTraitContext::disallowed(),
1469 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
1470 bounds: this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| {
1472 // Ignore `?Trait` bounds.
1473 // They were copied into type parameters already.
1474 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1476 this.lower_param_bound(bound, ImplTraitContext::disallowed()),
1484 WherePredicate::RegionPredicate(WhereRegionPredicate {
1488 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
1490 lifetime: self.lower_lifetime(lifetime),
1491 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
1493 WherePredicate::EqPredicate(WhereEqPredicate { id, ref lhs_ty, ref rhs_ty, span }) => {
1494 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
1495 hir_id: self.lower_node_id(id),
1496 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
1497 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
1505 /// Helper struct for delayed construction of Generics.
1506 pub(super) struct GenericsCtor<'hir> {
1507 pub(super) params: SmallVec<[hir::GenericParam<'hir>; 4]>,
1508 where_clause: hir::WhereClause<'hir>,
1512 impl<'hir> GenericsCtor<'hir> {
1513 pub(super) fn into_generics(self, arena: &'hir Arena<'hir>) -> hir::Generics<'hir> {
1515 params: arena.alloc_from_iter(self.params),
1516 where_clause: self.where_clause,