1 use super::LoweringContext;
2 use super::ImplTraitContext;
3 use super::ImplTraitPosition;
4 use super::ImplTraitTypeIdVisitor;
5 use super::AnonymousLifetimeMode;
8 use crate::hir::{self, HirVec};
9 use crate::hir::ptr::P;
10 use crate::hir::def_id::DefId;
11 use crate::hir::def::{Res, DefKind};
12 use crate::util::nodemap::NodeMap;
14 use rustc_data_structures::thin_vec::ThinVec;
15 use rustc_target::spec::abi;
17 use std::collections::BTreeSet;
18 use smallvec::SmallVec;
21 use syntax::visit::{self, Visitor};
22 use syntax::source_map::{respan, DesugaringKind};
23 use syntax::symbol::{kw, sym};
26 use rustc_error_codes::*;
28 pub(super) struct ItemLowerer<'tcx, 'interner> {
29 pub(super) lctx: &'tcx mut LoweringContext<'interner>,
32 impl<'tcx, 'interner> ItemLowerer<'tcx, 'interner> {
33 fn with_trait_impl_ref<F>(&mut self, trait_impl_ref: &Option<TraitRef>, f: F)
37 let old = self.lctx.is_in_trait_impl;
38 self.lctx.is_in_trait_impl = if let &None = trait_impl_ref {
44 self.lctx.is_in_trait_impl = old;
48 impl<'tcx, 'interner> Visitor<'tcx> for ItemLowerer<'tcx, 'interner> {
49 fn visit_mod(&mut self, m: &'tcx Mod, _s: Span, _attrs: &[Attribute], n: NodeId) {
50 let hir_id = self.lctx.lower_node_id(n);
52 self.lctx.modules.insert(hir_id, hir::ModuleItems {
53 items: BTreeSet::new(),
54 trait_items: BTreeSet::new(),
55 impl_items: BTreeSet::new(),
58 let old = self.lctx.current_module;
59 self.lctx.current_module = hir_id;
60 visit::walk_mod(self, m);
61 self.lctx.current_module = old;
64 fn visit_item(&mut self, item: &'tcx Item) {
65 let mut item_hir_id = None;
66 self.lctx.with_hir_id_owner(item.id, |lctx| {
67 lctx.without_in_scope_lifetime_defs(|lctx| {
68 if let Some(hir_item) = lctx.lower_item(item) {
69 item_hir_id = Some(hir_item.hir_id);
70 lctx.insert_item(hir_item);
75 if let Some(hir_id) = item_hir_id {
76 self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
77 let this = &mut ItemLowerer { lctx: this };
78 if let ItemKind::Impl(.., ref opt_trait_ref, _, _) = item.kind {
79 this.with_trait_impl_ref(opt_trait_ref, |this| {
80 visit::walk_item(this, item)
83 visit::walk_item(this, item);
89 fn visit_trait_item(&mut self, item: &'tcx AssocItem) {
90 self.lctx.with_hir_id_owner(item.id, |lctx| {
91 let hir_item = lctx.lower_trait_item(item);
92 let id = hir::TraitItemId { hir_id: hir_item.hir_id };
93 lctx.trait_items.insert(id, hir_item);
94 lctx.modules.get_mut(&lctx.current_module).unwrap().trait_items.insert(id);
97 visit::walk_trait_item(self, item);
100 fn visit_impl_item(&mut self, item: &'tcx AssocItem) {
101 self.lctx.with_hir_id_owner(item.id, |lctx| {
102 let hir_item = lctx.lower_impl_item(item);
103 let id = hir::ImplItemId { hir_id: hir_item.hir_id };
104 lctx.impl_items.insert(id, hir_item);
105 lctx.modules.get_mut(&lctx.current_module).unwrap().impl_items.insert(id);
107 visit::walk_impl_item(self, item);
111 impl LoweringContext<'_> {
112 // Same as the method above, but accepts `hir::GenericParam`s
113 // instead of `ast::GenericParam`s.
114 // This should only be used with generics that have already had their
115 // in-band lifetimes added. In practice, this means that this function is
116 // only used when lowering a child item of a trait or impl.
117 fn with_parent_item_lifetime_defs<T>(
119 parent_hir_id: hir::HirId,
120 f: impl FnOnce(&mut LoweringContext<'_>) -> T,
122 let old_len = self.in_scope_lifetimes.len();
124 let parent_generics = match self.items.get(&parent_hir_id).unwrap().kind {
125 hir::ItemKind::Impl(_, _, _, ref generics, ..)
126 | hir::ItemKind::Trait(_, _, ref generics, ..) => {
131 let lt_def_names = parent_generics.iter().filter_map(|param| match param.kind {
132 hir::GenericParamKind::Lifetime { .. } => Some(param.name.modern()),
135 self.in_scope_lifetimes.extend(lt_def_names);
139 self.in_scope_lifetimes.truncate(old_len);
143 // Clears (and restores) the `in_scope_lifetimes` field. Used when
144 // visiting nested items, which never inherit in-scope lifetimes
145 // from their surrounding environment.
146 fn without_in_scope_lifetime_defs<T>(
148 f: impl FnOnce(&mut LoweringContext<'_>) -> T,
150 let old_in_scope_lifetimes = std::mem::replace(&mut self.in_scope_lifetimes, vec![]);
152 // this vector is only used when walking over impl headers,
153 // input types, and the like, and should not be non-empty in
155 assert!(self.lifetimes_to_define.is_empty());
159 assert!(self.in_scope_lifetimes.is_empty());
160 self.in_scope_lifetimes = old_in_scope_lifetimes;
165 pub(super) fn lower_mod(&mut self, m: &Mod) -> hir::Mod {
168 item_ids: m.items.iter().flat_map(|x| self.lower_item_id(x)).collect(),
172 pub(super) fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
173 let node_ids = match i.kind {
174 ItemKind::Use(ref use_tree) => {
175 let mut vec = smallvec![i.id];
176 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
179 ItemKind::MacroDef(..) => SmallVec::new(),
181 ItemKind::Impl(.., None, _, _) => smallvec![i.id],
182 ItemKind::Static(ref ty, ..) => {
183 let mut ids = smallvec![i.id];
184 if self.sess.features_untracked().impl_trait_in_bindings {
185 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
186 visitor.visit_ty(ty);
190 ItemKind::Const(ref ty, ..) => {
191 let mut ids = smallvec![i.id];
192 if self.sess.features_untracked().impl_trait_in_bindings {
193 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
194 visitor.visit_ty(ty);
198 _ => smallvec![i.id],
201 node_ids.into_iter().map(|node_id| hir::ItemId {
202 id: self.allocate_hir_id_counter(node_id)
206 fn lower_item_id_use_tree(
210 vec: &mut SmallVec<[NodeId; 1]>
213 UseTreeKind::Nested(ref nested_vec) => for &(ref nested, id) in nested_vec {
215 self.lower_item_id_use_tree(nested, id, vec);
217 UseTreeKind::Glob => {}
218 UseTreeKind::Simple(_, id1, id2) => {
219 for (_, &id) in self.expect_full_res_from_use(base_id)
221 .zip([id1, id2].iter())
229 pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item> {
230 let mut ident = i.ident;
231 let mut vis = self.lower_visibility(&i.vis, None);
232 let attrs = self.lower_attrs(&i.attrs);
234 if let ItemKind::MacroDef(ref def) = i.kind {
235 if !def.legacy || attr::contains_name(&i.attrs, sym::macro_export) {
236 let body = self.lower_token_stream(def.body.inner_tokens());
237 let hir_id = self.lower_node_id(i.id);
238 self.exported_macros.push(hir::MacroDef {
248 self.non_exported_macro_attrs.extend(attrs.into_iter());
253 let kind = self.lower_item_kind(i.span, i.id, &mut ident, &attrs, &mut vis, &i.kind);
256 hir_id: self.lower_node_id(i.id),
270 attrs: &hir::HirVec<Attribute>,
271 vis: &mut hir::Visibility,
275 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
276 ItemKind::Use(ref use_tree) => {
277 // Start with an empty prefix.
283 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
285 ItemKind::Static(ref t, m, ref e) => {
286 hir::ItemKind::Static(
289 if self.sess.features_untracked().impl_trait_in_bindings {
290 ImplTraitContext::OpaqueTy(None)
292 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
296 self.lower_const_body(span, Some(e)),
299 ItemKind::Const(ref t, ref e) => {
300 hir::ItemKind::Const(
303 if self.sess.features_untracked().impl_trait_in_bindings {
304 ImplTraitContext::OpaqueTy(None)
306 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
309 self.lower_const_body(span, Some(e))
312 ItemKind::Fn(FnSig { ref decl, header }, ref generics, ref body) => {
313 let fn_def_id = self.resolver.definitions().local_def_id(id);
314 self.with_new_scopes(|this| {
315 this.current_item = Some(ident.span);
317 // Note: we don't need to change the return type from `T` to
318 // `impl Future<Output = T>` here because lower_body
319 // only cares about the input argument patterns in the function
320 // declaration (decl), not the return types.
321 let body_id = this.lower_maybe_async_body(
324 header.asyncness.node,
328 let (generics, decl) = this.add_in_band_defs(
331 AnonymousLifetimeMode::PassThrough,
332 |this, idty| this.lower_fn_decl(
334 Some((fn_def_id, idty)),
336 header.asyncness.node.opt_return_id()
339 let sig = hir::FnSig { decl, header: this.lower_fn_header(header) };
340 hir::ItemKind::Fn(sig, generics, body_id)
343 ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
344 ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
345 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
346 ItemKind::TyAlias(ref ty, ref generics) => match ty.kind.opaque_top_hack() {
348 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
349 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
350 hir::ItemKind::TyAlias(ty, generics)
353 let ty = hir::OpaqueTy {
354 generics: self.lower_generics(generics, ImplTraitContext::OpaqueTy(None)),
355 bounds: self.lower_param_bounds(bounds, ImplTraitContext::OpaqueTy(None)),
357 origin: hir::OpaqueTyOrigin::TypeAlias,
359 hir::ItemKind::OpaqueTy(ty)
362 ItemKind::Enum(ref enum_definition, ref generics) => {
365 variants: enum_definition
368 .map(|x| self.lower_variant(x))
371 self.lower_generics(generics, ImplTraitContext::disallowed()),
374 ItemKind::Struct(ref struct_def, ref generics) => {
375 let struct_def = self.lower_variant_data(struct_def);
376 hir::ItemKind::Struct(
378 self.lower_generics(generics, ImplTraitContext::disallowed()),
381 ItemKind::Union(ref vdata, ref generics) => {
382 let vdata = self.lower_variant_data(vdata);
383 hir::ItemKind::Union(
385 self.lower_generics(generics, ImplTraitContext::disallowed()),
397 let def_id = self.resolver.definitions().local_def_id(id);
399 // Lower the "impl header" first. This ordering is important
400 // for in-band lifetimes! Consider `'a` here:
402 // impl Foo<'a> for u32 {
403 // fn method(&'a self) { .. }
406 // Because we start by lowering the `Foo<'a> for u32`
407 // part, we will add `'a` to the list of generics on
408 // the impl. When we then encounter it later in the
409 // method, it will not be considered an in-band
410 // lifetime to be added, but rather a reference to a
412 let lowered_trait_impl_id = self.lower_node_id(id);
413 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
416 AnonymousLifetimeMode::CreateParameter,
418 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
419 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
422 if let Some(ref trait_ref) = trait_ref {
423 if let Res::Def(DefKind::Trait, def_id) = trait_ref.path.res {
424 this.trait_impls.entry(def_id).or_default().push(
425 lowered_trait_impl_id);
429 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
431 (trait_ref, lowered_ty)
435 let new_impl_items = self.with_in_scope_lifetime_defs(
436 &ast_generics.params,
440 .map(|item| this.lower_impl_item_ref(item))
448 self.lower_defaultness(defaultness, true /* [1] */),
455 ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
456 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
459 .map(|item| self.lower_trait_item_ref(item))
461 hir::ItemKind::Trait(
464 self.lower_generics(generics, ImplTraitContext::disallowed()),
469 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
470 self.lower_generics(generics, ImplTraitContext::disallowed()),
471 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
473 ItemKind::MacroDef(..)
474 | ItemKind::Mac(..) => bug!("`TyMac` should have been expanded by now"),
477 // [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to
478 // not cause an assertion failure inside the `lower_defaultness` function.
486 vis: &mut hir::Visibility,
488 attrs: &hir::HirVec<Attribute>,
490 debug!("lower_use_tree(tree={:?})", tree);
491 debug!("lower_use_tree: vis = {:?}", vis);
493 let path = &tree.prefix;
494 let segments = prefix
497 .chain(path.segments.iter())
502 UseTreeKind::Simple(rename, id1, id2) => {
503 *ident = tree.ident();
505 // First, apply the prefix to the path.
506 let mut path = Path {
511 // Correctly resolve `self` imports.
512 if path.segments.len() > 1
513 && path.segments.last().unwrap().ident.name == kw::SelfLower
515 let _ = path.segments.pop();
516 if rename.is_none() {
517 *ident = path.segments.last().unwrap().ident;
521 let mut resolutions = self.expect_full_res_from_use(id);
522 // We want to return *something* from this function, so hold onto the first item
524 let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
526 // Here, we are looping over namespaces, if they exist for the definition
527 // being imported. We only handle type and value namespaces because we
528 // won't be dealing with macros in the rest of the compiler.
529 // Essentially a single `use` which imports two names is desugared into
531 for (res, &new_node_id) in resolutions.zip([id1, id2].iter()) {
533 let mut path = path.clone();
534 for seg in &mut path.segments {
535 seg.id = self.resolver.next_node_id();
537 let span = path.span;
539 self.with_hir_id_owner(new_node_id, |this| {
540 let new_id = this.lower_node_id(new_node_id);
541 let res = this.lower_res(res);
543 this.lower_path_extra(res, &path, ParamMode::Explicit, None);
544 let kind = hir::ItemKind::Use(P(path), hir::UseKind::Single);
545 let vis = this.rebuild_vis(&vis);
551 attrs: attrs.into_iter().cloned().collect(),
560 let path = P(self.lower_path_extra(ret_res, &path, ParamMode::Explicit, None));
561 hir::ItemKind::Use(path, hir::UseKind::Single)
563 UseTreeKind::Glob => {
564 let path = P(self.lower_path(
572 hir::ItemKind::Use(path, hir::UseKind::Glob)
574 UseTreeKind::Nested(ref trees) => {
575 // Nested imports are desugared into simple imports.
576 // So, if we start with
579 // pub(x) use foo::{a, b};
582 // we will create three items:
585 // pub(x) use foo::a;
586 // pub(x) use foo::b;
587 // pub(x) use foo::{}; // <-- this is called the `ListStem`
590 // The first two are produced by recursively invoking
591 // `lower_use_tree` (and indeed there may be things
592 // like `use foo::{a::{b, c}}` and so forth). They
593 // wind up being directly added to
594 // `self.items`. However, the structure of this
595 // function also requires us to return one item, and
596 // for that we return the `{}` import (called the
601 span: prefix.span.to(path.span),
604 // Add all the nested `PathListItem`s to the HIR.
605 for &(ref use_tree, id) in trees {
606 let new_hir_id = self.lower_node_id(id);
608 let mut prefix = prefix.clone();
610 // Give the segments new node-ids since they are being cloned.
611 for seg in &mut prefix.segments {
612 seg.id = self.resolver.next_node_id();
615 // Each `use` import is an item and thus are owners of the
616 // names in the path. Up to this point the nested import is
617 // the current owner, since we want each desugared import to
618 // own its own names, we have to adjust the owner before
619 // lowering the rest of the import.
620 self.with_hir_id_owner(id, |this| {
621 let mut vis = this.rebuild_vis(&vis);
622 let mut ident = *ident;
624 let kind = this.lower_use_tree(use_tree,
635 attrs: attrs.into_iter().cloned().collect(),
644 // Subtle and a bit hacky: we lower the privacy level
645 // of the list stem to "private" most of the time, but
646 // not for "restricted" paths. The key thing is that
647 // we don't want it to stay as `pub` (with no caveats)
648 // because that affects rustdoc and also the lints
649 // about `pub` items. But we can't *always* make it
650 // private -- particularly not for restricted paths --
651 // because it contains node-ids that would then be
652 // unused, failing the check that HirIds are "densely
655 hir::VisibilityKind::Public |
656 hir::VisibilityKind::Crate(_) |
657 hir::VisibilityKind::Inherited => {
658 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
660 hir::VisibilityKind::Restricted { .. } => {
661 // Do nothing here, as described in the comment on the match.
665 let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
666 let res = self.lower_res(res);
667 let path = P(self.lower_path_extra(res, &prefix, ParamMode::Explicit, None));
668 hir::ItemKind::Use(path, hir::UseKind::ListStem)
673 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
674 /// many times in the HIR tree; for each occurrence, we need to assign distinct
675 /// `NodeId`s. (See, e.g., #56128.)
676 fn rebuild_use_path(&mut self, path: &hir::Path) -> hir::Path {
677 debug!("rebuild_use_path(path = {:?})", path);
678 let segments = path.segments.iter().map(|seg| hir::PathSegment {
680 hir_id: seg.hir_id.map(|_| self.next_id()),
683 infer_args: seg.infer_args,
692 fn rebuild_vis(&mut self, vis: &hir::Visibility) -> hir::Visibility {
693 let vis_kind = match vis.node {
694 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
695 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
696 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
697 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
698 hir::VisibilityKind::Restricted {
699 path: P(self.rebuild_use_path(path)),
700 hir_id: self.next_id(),
704 respan(vis.span, vis_kind)
707 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem {
708 let def_id = self.resolver.definitions().local_def_id(i.id);
710 hir_id: self.lower_node_id(i.id),
712 attrs: self.lower_attrs(&i.attrs),
714 ForeignItemKind::Fn(ref fdec, ref generics) => {
715 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
718 AnonymousLifetimeMode::PassThrough,
721 // Disallow `impl Trait` in foreign items.
722 this.lower_fn_decl(fdec, None, false, None),
723 this.lower_fn_params_to_names(fdec),
728 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
730 ForeignItemKind::Static(ref t, m) => {
731 hir::ForeignItemKind::Static(
732 self.lower_ty(t, ImplTraitContext::disallowed()), m)
734 ForeignItemKind::Ty => hir::ForeignItemKind::Type,
735 ForeignItemKind::Macro(_) => panic!("macro shouldn't exist here"),
737 vis: self.lower_visibility(&i.vis, None),
742 fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod {
744 abi: fm.abi.map_or(abi::Abi::C, |abi| self.lower_abi(abi)),
747 .map(|x| self.lower_foreign_item(x))
752 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> P<hir::GlobalAsm> {
753 P(hir::GlobalAsm { asm: ga.asm })
756 fn lower_variant(&mut self, v: &Variant) -> hir::Variant {
758 attrs: self.lower_attrs(&v.attrs),
759 data: self.lower_variant_data(&v.data),
760 disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
761 id: self.lower_node_id(v.id),
767 fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData {
769 VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
770 fields.iter().enumerate().map(|f| self.lower_struct_field(f)).collect(),
773 VariantData::Tuple(ref fields, id) => {
774 hir::VariantData::Tuple(
778 .map(|f| self.lower_struct_field(f))
780 self.lower_node_id(id),
783 VariantData::Unit(id) => {
784 hir::VariantData::Unit(self.lower_node_id(id))
789 fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField {
790 let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
791 let t = self.lower_path_ty(
795 ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
796 ImplTraitContext::disallowed()
800 self.lower_ty(&f.ty, ImplTraitContext::disallowed())
804 hir_id: self.lower_node_id(f.id),
805 ident: match f.ident {
806 Some(ident) => ident,
807 // FIXME(jseyfried): positional field hygiene.
808 None => Ident::new(sym::integer(index), f.span),
810 vis: self.lower_visibility(&f.vis, None),
812 attrs: self.lower_attrs(&f.attrs),
816 fn lower_trait_item(&mut self, i: &AssocItem) -> hir::TraitItem {
817 let trait_item_def_id = self.resolver.definitions().local_def_id(i.id);
819 let (generics, kind) = match i.kind {
820 AssocItemKind::Const(ref ty, ref default) => (
821 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
822 hir::TraitItemKind::Const(
823 self.lower_ty(ty, ImplTraitContext::disallowed()),
826 .map(|x| self.lower_const_body(i.span, Some(x))),
829 AssocItemKind::Fn(ref sig, None) => {
830 let names = self.lower_fn_params_to_names(&sig.decl);
831 let (generics, sig) = self.lower_method_sig(
838 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Required(names)))
840 AssocItemKind::Fn(ref sig, Some(ref body)) => {
841 let body_id = self.lower_fn_body_block(i.span, &sig.decl, Some(body));
842 let (generics, sig) = self.lower_method_sig(
849 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Provided(body_id)))
851 AssocItemKind::TyAlias(ref bounds, ref default) => {
852 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
853 let kind = hir::TraitItemKind::Type(
854 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
857 .map(|x| self.lower_ty(x, ImplTraitContext::disallowed())),
862 AssocItemKind::Macro(..) => bug!("macro item shouldn't exist at this point"),
866 hir_id: self.lower_node_id(i.id),
868 attrs: self.lower_attrs(&i.attrs),
875 fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef {
876 let (kind, has_default) = match i.kind {
877 AssocItemKind::Const(_, ref default) => {
878 (hir::AssocItemKind::Const, default.is_some())
880 AssocItemKind::TyAlias(_, ref default) => {
881 (hir::AssocItemKind::Type, default.is_some())
883 AssocItemKind::Fn(ref sig, ref default) => (
884 hir::AssocItemKind::Method {
885 has_self: sig.decl.has_self(),
889 AssocItemKind::Macro(..) => unimplemented!(),
892 id: hir::TraitItemId { hir_id: self.lower_node_id(i.id) },
895 defaultness: self.lower_defaultness(Defaultness::Default, has_default),
900 /// Construct `ExprKind::Err` for the given `span`.
901 fn expr_err(&mut self, span: Span) -> hir::Expr {
902 self.expr(span, hir::ExprKind::Err, ThinVec::new())
905 fn lower_impl_item(&mut self, i: &AssocItem) -> hir::ImplItem {
906 let impl_item_def_id = self.resolver.definitions().local_def_id(i.id);
908 let (generics, kind) = match i.kind {
909 AssocItemKind::Const(ref ty, ref expr) => (
910 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
911 hir::ImplItemKind::Const(
912 self.lower_ty(ty, ImplTraitContext::disallowed()),
913 self.lower_const_body(i.span, expr.as_deref()),
916 AssocItemKind::Fn(ref sig, ref body) => {
917 self.current_item = Some(i.span);
918 let body_id = self.lower_maybe_async_body(
921 sig.header.asyncness.node,
924 let impl_trait_return_allow = !self.is_in_trait_impl;
925 let (generics, sig) = self.lower_method_sig(
929 impl_trait_return_allow,
930 sig.header.asyncness.node.opt_return_id(),
933 (generics, hir::ImplItemKind::Method(sig, body_id))
935 AssocItemKind::TyAlias(_, ref ty) => {
936 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
937 let kind = match ty {
939 hir::ImplItemKind::TyAlias(P(self.ty(i.span, hir::TyKind::Err)))
941 Some(ty) => match ty.kind.opaque_top_hack() {
943 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
944 hir::ImplItemKind::TyAlias(ty)
947 let bs = self.lower_param_bounds(bs, ImplTraitContext::disallowed());
948 hir::ImplItemKind::OpaqueTy(bs)
954 AssocItemKind::Macro(..) => bug!("`TyMac` should have been expanded by now"),
958 hir_id: self.lower_node_id(i.id),
960 attrs: self.lower_attrs(&i.attrs),
962 vis: self.lower_visibility(&i.vis, None),
963 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
968 // [1] since `default impl` is not yet implemented, this is always true in impls
971 fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef {
973 id: hir::ImplItemId { hir_id: self.lower_node_id(i.id) },
976 vis: self.lower_visibility(&i.vis, Some(i.id)),
977 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
978 kind: match &i.kind {
979 AssocItemKind::Const(..) => hir::AssocItemKind::Const,
980 AssocItemKind::TyAlias(_, ty) => match ty
982 .and_then(|ty| ty.kind.opaque_top_hack())
984 None => hir::AssocItemKind::Type,
985 Some(_) => hir::AssocItemKind::OpaqueTy,
987 AssocItemKind::Fn(sig, _) => hir::AssocItemKind::Method {
988 has_self: sig.decl.has_self(),
990 AssocItemKind::Macro(..) => unimplemented!(),
994 // [1] since `default impl` is not yet implemented, this is always true in impls
997 /// If an `explicit_owner` is given, this method allocates the `HirId` in
998 /// the address space of that item instead of the item currently being
999 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
1000 /// lower a `Visibility` value although we haven't lowered the owning
1001 /// `ImplItem` in question yet.
1002 fn lower_visibility(
1005 explicit_owner: Option<NodeId>,
1006 ) -> hir::Visibility {
1007 let node = match v.node {
1008 VisibilityKind::Public => hir::VisibilityKind::Public,
1009 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
1010 VisibilityKind::Restricted { ref path, id } => {
1011 debug!("lower_visibility: restricted path id = {:?}", id);
1012 let lowered_id = if let Some(owner) = explicit_owner {
1013 self.lower_node_id_with_owner(id, owner)
1015 self.lower_node_id(id)
1017 let res = self.expect_full_res(id);
1018 let res = self.lower_res(res);
1019 hir::VisibilityKind::Restricted {
1020 path: P(self.lower_path_extra(
1023 ParamMode::Explicit,
1029 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
1031 respan(v.span, node)
1034 fn lower_defaultness(&self, d: Defaultness, has_value: bool) -> hir::Defaultness {
1036 Defaultness::Default => hir::Defaultness::Default {
1037 has_value: has_value,
1039 Defaultness::Final => {
1041 hir::Defaultness::Final
1046 fn record_body(&mut self, params: HirVec<hir::Param>, value: hir::Expr) -> hir::BodyId {
1047 let body = hir::Body {
1048 generator_kind: self.generator_kind,
1053 self.bodies.insert(id, body);
1059 f: impl FnOnce(&mut LoweringContext<'_>) -> (HirVec<hir::Param>, hir::Expr),
1061 let prev_gen_kind = self.generator_kind.take();
1062 let (parameters, result) = f(self);
1063 let body_id = self.record_body(parameters, result);
1064 self.generator_kind = prev_gen_kind;
1068 fn lower_param(&mut self, param: &Param) -> hir::Param {
1070 attrs: self.lower_attrs(¶m.attrs),
1071 hir_id: self.lower_node_id(param.id),
1072 pat: self.lower_pat(¶m.pat),
1077 pub(super) fn lower_fn_body(
1080 body: impl FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
1082 self.lower_body(|this| (
1083 decl.inputs.iter().map(|x| this.lower_param(x)).collect(),
1088 fn lower_fn_body_block(
1092 body: Option<&Block>,
1094 self.lower_fn_body(decl, |this| this.lower_block_expr_opt(span, body))
1097 fn lower_block_expr_opt(&mut self, span: Span, block: Option<&Block>) -> hir::Expr {
1099 Some(block) => self.lower_block_expr(block),
1100 None => self.expr_err(span),
1104 pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
1105 self.lower_body(|this| (hir_vec![], match expr {
1106 Some(expr) => this.lower_expr(expr),
1107 None => this.expr_err(span),
1111 fn lower_maybe_async_body(
1116 body: Option<&Block>,
1118 let closure_id = match asyncness {
1119 IsAsync::Async { closure_id, .. } => closure_id,
1120 IsAsync::NotAsync => return self.lower_fn_body_block(span, decl, body),
1123 self.lower_body(|this| {
1124 let mut parameters: Vec<hir::Param> = Vec::new();
1125 let mut statements: Vec<hir::Stmt> = Vec::new();
1127 // Async function parameters are lowered into the closure body so that they are
1128 // captured and so that the drop order matches the equivalent non-async functions.
1132 // async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
1138 // fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
1140 // let __arg2 = __arg2;
1141 // let <pattern> = __arg2;
1142 // let __arg1 = __arg1;
1143 // let <pattern> = __arg1;
1144 // let __arg0 = __arg0;
1145 // let <pattern> = __arg0;
1146 // drop-temps { <body> } // see comments later in fn for details
1150 // If `<pattern>` is a simple ident, then it is lowered to a single
1151 // `let <pattern> = <pattern>;` statement as an optimization.
1153 // Note that the body is embedded in `drop-temps`; an
1154 // equivalent desugaring would be `return { <body>
1155 // };`. The key point is that we wish to drop all the
1156 // let-bound variables and temporaries created in the body
1157 // (and its tail expression!) before we drop the
1158 // parameters (c.f. rust-lang/rust#64512).
1159 for (index, parameter) in decl.inputs.iter().enumerate() {
1160 let parameter = this.lower_param(parameter);
1161 let span = parameter.pat.span;
1163 // Check if this is a binding pattern, if so, we can optimize and avoid adding a
1164 // `let <pat> = __argN;` statement. In this case, we do not rename the parameter.
1165 let (ident, is_simple_parameter) = match parameter.pat.kind {
1166 hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, ident, _) =>
1169 // Replace the ident for bindings that aren't simple.
1170 let name = format!("__arg{}", index);
1171 let ident = Ident::from_str(&name);
1177 let desugared_span =
1178 this.mark_span_with_reason(DesugaringKind::Async, span, None);
1180 // Construct a parameter representing `__argN: <ty>` to replace the parameter of the
1183 // If this is the simple case, this parameter will end up being the same as the
1184 // original parameter, but with a different pattern id.
1185 let mut stmt_attrs = ThinVec::new();
1186 stmt_attrs.extend(parameter.attrs.iter().cloned());
1187 let (new_parameter_pat, new_parameter_id) = this.pat_ident(desugared_span, ident);
1188 let new_parameter = hir::Param {
1189 attrs: parameter.attrs,
1190 hir_id: parameter.hir_id,
1191 pat: new_parameter_pat,
1192 span: parameter.span,
1196 if is_simple_parameter {
1197 // If this is the simple case, then we only insert one statement that is
1198 // `let <pat> = <pat>;`. We re-use the original argument's pattern so that
1199 // `HirId`s are densely assigned.
1200 let expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1201 let stmt = this.stmt_let_pat(
1206 hir::LocalSource::AsyncFn
1208 statements.push(stmt);
1210 // If this is not the simple case, then we construct two statements:
1213 // let __argN = __argN;
1214 // let <pat> = __argN;
1217 // The first statement moves the parameter into the closure and thus ensures
1218 // that the drop order is correct.
1220 // The second statement creates the bindings that the user wrote.
1222 // Construct the `let mut __argN = __argN;` statement. It must be a mut binding
1223 // because the user may have specified a `ref mut` binding in the next
1225 let (move_pat, move_id) = this.pat_ident_binding_mode(
1226 desugared_span, ident, hir::BindingAnnotation::Mutable);
1227 let move_expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1228 let move_stmt = this.stmt_let_pat(
1233 hir::LocalSource::AsyncFn
1236 // Construct the `let <pat> = __argN;` statement. We re-use the original
1237 // parameter's pattern so that `HirId`s are densely assigned.
1238 let pattern_expr = this.expr_ident(desugared_span, ident, move_id);
1239 let pattern_stmt = this.stmt_let_pat(
1242 Some(P(pattern_expr)),
1244 hir::LocalSource::AsyncFn
1247 statements.push(move_stmt);
1248 statements.push(pattern_stmt);
1251 parameters.push(new_parameter);
1254 let body_span = body.map_or(span, |b| b.span);
1255 let async_expr = this.make_async_expr(
1260 hir::AsyncGeneratorKind::Fn,
1262 // Create a block from the user's function body:
1263 let user_body = this.lower_block_expr_opt(body_span, body);
1265 // Transform into `drop-temps { <user-body> }`, an expression:
1266 let desugared_span = this.mark_span_with_reason(
1267 DesugaringKind::Async,
1271 let user_body = this.expr_drop_temps(
1277 // As noted above, create the final block like
1281 // let $param_pattern = $raw_param;
1283 // drop-temps { <user-body> }
1286 let body = this.block_all(
1291 this.expr_block(P(body), ThinVec::new())
1293 (HirVec::from(parameters), this.expr(body_span, async_expr, ThinVec::new()))
1297 fn lower_method_sig(
1299 generics: &Generics,
1302 impl_trait_return_allow: bool,
1303 is_async: Option<NodeId>,
1304 ) -> (hir::Generics, hir::FnSig) {
1305 let header = self.lower_fn_header(sig.header);
1306 let (generics, decl) = self.add_in_band_defs(
1309 AnonymousLifetimeMode::PassThrough,
1310 |this, idty| this.lower_fn_decl(
1312 Some((fn_def_id, idty)),
1313 impl_trait_return_allow,
1317 (generics, hir::FnSig { header, decl })
1320 fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
1322 unsafety: h.unsafety,
1323 asyncness: self.lower_asyncness(h.asyncness.node),
1324 constness: h.constness.node,
1325 abi: self.lower_extern(h.ext),
1329 pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
1330 abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
1331 self.error_on_invalid_abi(abi);
1336 pub(super) fn lower_extern(&mut self, ext: Extern) -> abi::Abi {
1338 Extern::None => abi::Abi::Rust,
1339 Extern::Implicit => abi::Abi::C,
1340 Extern::Explicit(abi) => self.lower_abi(abi),
1344 fn error_on_invalid_abi(&self, abi: StrLit) {
1349 "invalid ABI: found `{}`",
1352 .span_label(abi.span, "invalid ABI")
1353 .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
1357 fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
1359 IsAsync::Async { .. } => hir::IsAsync::Async,
1360 IsAsync::NotAsync => hir::IsAsync::NotAsync,
1364 pub(super) fn lower_generics(
1366 generics: &Generics,
1367 itctx: ImplTraitContext<'_>)
1370 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
1371 // FIXME: this could probably be done with less rightward drift. It also looks like two
1372 // control paths where `report_error` is called are the only paths that advance to after the
1373 // match statement, so the error reporting could probably just be moved there.
1374 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
1375 for pred in &generics.where_clause.predicates {
1376 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
1377 'next_bound: for bound in &bound_pred.bounds {
1378 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
1379 let report_error = |this: &mut Self| {
1380 this.diagnostic().span_err(
1381 bound_pred.bounded_ty.span,
1382 "`?Trait` bounds are only permitted at the \
1383 point where a type parameter is declared",
1386 // Check if the where clause type is a plain type parameter.
1387 match bound_pred.bounded_ty.kind {
1388 TyKind::Path(None, ref path)
1389 if path.segments.len() == 1
1390 && bound_pred.bound_generic_params.is_empty() =>
1392 if let Some(Res::Def(DefKind::TyParam, def_id)) = self.resolver
1393 .get_partial_res(bound_pred.bounded_ty.id)
1394 .map(|d| d.base_res())
1396 if let Some(node_id) =
1397 self.resolver.definitions().as_local_node_id(def_id)
1399 for param in &generics.params {
1401 GenericParamKind::Type { .. } => {
1402 if node_id == param.id {
1403 add_bounds.entry(param.id)
1405 .push(bound.clone());
1406 continue 'next_bound;
1416 _ => report_error(self),
1424 params: self.lower_generic_params(&generics.params, &add_bounds, itctx),
1425 where_clause: self.lower_where_clause(&generics.where_clause),
1426 span: generics.span,
1430 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause {
1431 self.with_anonymous_lifetime_mode(
1432 AnonymousLifetimeMode::ReportError,
1435 predicates: wc.predicates
1437 .map(|predicate| this.lower_where_predicate(predicate))
1445 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate {
1447 WherePredicate::BoundPredicate(WhereBoundPredicate {
1448 ref bound_generic_params,
1453 self.with_in_scope_lifetime_defs(
1454 &bound_generic_params,
1456 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
1457 bound_generic_params: this.lower_generic_params(
1458 bound_generic_params,
1459 &NodeMap::default(),
1460 ImplTraitContext::disallowed(),
1462 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
1465 .filter_map(|bound| match *bound {
1466 // Ignore `?Trait` bounds.
1467 // They were copied into type parameters already.
1468 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1469 _ => Some(this.lower_param_bound(
1471 ImplTraitContext::disallowed(),
1480 WherePredicate::RegionPredicate(WhereRegionPredicate {
1484 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
1486 lifetime: self.lower_lifetime(lifetime),
1487 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
1489 WherePredicate::EqPredicate(WhereEqPredicate {
1495 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
1496 hir_id: self.lower_node_id(id),
1497 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
1498 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),