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_target::spec::abi;
16 use std::collections::BTreeSet;
17 use smallvec::SmallVec;
20 use syntax::visit::{self, Visitor};
21 use syntax::source_map::{respan, DesugaringKind};
22 use syntax::symbol::{kw, sym};
25 use rustc_error_codes::*;
27 pub(super) struct ItemLowerer<'tcx, 'interner> {
28 pub(super) lctx: &'tcx mut LoweringContext<'interner>,
31 impl<'tcx, 'interner> ItemLowerer<'tcx, 'interner> {
32 fn with_trait_impl_ref<F>(&mut self, trait_impl_ref: &Option<TraitRef>, f: F)
36 let old = self.lctx.is_in_trait_impl;
37 self.lctx.is_in_trait_impl = if let &None = trait_impl_ref {
43 self.lctx.is_in_trait_impl = old;
47 impl<'tcx, 'interner> Visitor<'tcx> for ItemLowerer<'tcx, 'interner> {
48 fn visit_mod(&mut self, m: &'tcx Mod, _s: Span, _attrs: &[Attribute], n: NodeId) {
49 let hir_id = self.lctx.lower_node_id(n);
51 self.lctx.modules.insert(hir_id, hir::ModuleItems {
52 items: BTreeSet::new(),
53 trait_items: BTreeSet::new(),
54 impl_items: BTreeSet::new(),
57 let old = self.lctx.current_module;
58 self.lctx.current_module = hir_id;
59 visit::walk_mod(self, m);
60 self.lctx.current_module = old;
63 fn visit_item(&mut self, item: &'tcx Item) {
64 let mut item_hir_id = None;
65 self.lctx.with_hir_id_owner(item.id, |lctx| {
66 lctx.without_in_scope_lifetime_defs(|lctx| {
67 if let Some(hir_item) = lctx.lower_item(item) {
68 item_hir_id = Some(hir_item.hir_id);
69 lctx.insert_item(hir_item);
74 if let Some(hir_id) = item_hir_id {
75 self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
76 let this = &mut ItemLowerer { lctx: this };
77 if let ItemKind::Impl(.., ref opt_trait_ref, _, _) = item.kind {
78 this.with_trait_impl_ref(opt_trait_ref, |this| {
79 visit::walk_item(this, item)
82 visit::walk_item(this, item);
88 fn visit_trait_item(&mut self, item: &'tcx AssocItem) {
89 self.lctx.with_hir_id_owner(item.id, |lctx| {
90 let hir_item = lctx.lower_trait_item(item);
91 let id = hir::TraitItemId { hir_id: hir_item.hir_id };
92 lctx.trait_items.insert(id, hir_item);
93 lctx.modules.get_mut(&lctx.current_module).unwrap().trait_items.insert(id);
96 visit::walk_trait_item(self, item);
99 fn visit_impl_item(&mut self, item: &'tcx AssocItem) {
100 self.lctx.with_hir_id_owner(item.id, |lctx| {
101 let hir_item = lctx.lower_impl_item(item);
102 let id = hir::ImplItemId { hir_id: hir_item.hir_id };
103 lctx.impl_items.insert(id, hir_item);
104 lctx.modules.get_mut(&lctx.current_module).unwrap().impl_items.insert(id);
106 visit::walk_impl_item(self, item);
110 impl LoweringContext<'_> {
111 // Same as the method above, but accepts `hir::GenericParam`s
112 // instead of `ast::GenericParam`s.
113 // This should only be used with generics that have already had their
114 // in-band lifetimes added. In practice, this means that this function is
115 // only used when lowering a child item of a trait or impl.
116 fn with_parent_item_lifetime_defs<T>(
118 parent_hir_id: hir::HirId,
119 f: impl FnOnce(&mut LoweringContext<'_>) -> T,
121 let old_len = self.in_scope_lifetimes.len();
123 let parent_generics = match self.items.get(&parent_hir_id).unwrap().kind {
124 hir::ItemKind::Impl(_, _, _, ref generics, ..)
125 | hir::ItemKind::Trait(_, _, ref generics, ..) => {
130 let lt_def_names = parent_generics.iter().filter_map(|param| match param.kind {
131 hir::GenericParamKind::Lifetime { .. } => Some(param.name.modern()),
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 = std::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, m: &Mod) -> hir::Mod {
167 item_ids: m.items.iter().flat_map(|x| self.lower_item_id(x)).collect(),
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(),
180 ItemKind::Impl(.., None, _, _) => smallvec![i.id],
181 ItemKind::Static(ref ty, ..) => {
182 let mut ids = smallvec![i.id];
183 if self.sess.features_untracked().impl_trait_in_bindings {
184 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
185 visitor.visit_ty(ty);
189 ItemKind::Const(ref ty, ..) => {
190 let mut ids = smallvec![i.id];
191 if self.sess.features_untracked().impl_trait_in_bindings {
192 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
193 visitor.visit_ty(ty);
197 _ => smallvec![i.id],
200 node_ids.into_iter().map(|node_id| hir::ItemId {
201 id: self.allocate_hir_id_counter(node_id)
205 fn lower_item_id_use_tree(
209 vec: &mut SmallVec<[NodeId; 1]>
212 UseTreeKind::Nested(ref nested_vec) => for &(ref nested, id) in nested_vec {
214 self.lower_item_id_use_tree(nested, id, vec);
216 UseTreeKind::Glob => {}
217 UseTreeKind::Simple(_, id1, id2) => {
218 for (_, &id) in self.expect_full_res_from_use(base_id)
220 .zip([id1, id2].iter())
228 pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item> {
229 let mut ident = i.ident;
230 let mut vis = self.lower_visibility(&i.vis, None);
231 let attrs = self.lower_attrs(&i.attrs);
233 if let ItemKind::MacroDef(ref def) = i.kind {
234 if !def.legacy || attr::contains_name(&i.attrs, sym::macro_export) {
235 let body = self.lower_token_stream(def.body.inner_tokens());
236 let hir_id = self.lower_node_id(i.id);
237 self.exported_macros.push(hir::MacroDef {
247 self.non_exported_macro_attrs.extend(attrs.into_iter());
252 let kind = self.lower_item_kind(i.span, i.id, &mut ident, &attrs, &mut vis, &i.kind);
255 hir_id: self.lower_node_id(i.id),
269 attrs: &hir::HirVec<Attribute>,
270 vis: &mut hir::Visibility,
274 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
275 ItemKind::Use(ref use_tree) => {
276 // Start with an empty prefix.
282 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
284 ItemKind::Static(ref t, m, ref e) => {
285 hir::ItemKind::Static(
288 if self.sess.features_untracked().impl_trait_in_bindings {
289 ImplTraitContext::OpaqueTy(None)
291 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
295 self.lower_const_body(span, Some(e)),
298 ItemKind::Const(ref t, ref e) => {
299 hir::ItemKind::Const(
302 if self.sess.features_untracked().impl_trait_in_bindings {
303 ImplTraitContext::OpaqueTy(None)
305 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
308 self.lower_const_body(span, Some(e))
311 ItemKind::Fn(FnSig { ref decl, header }, ref generics, ref body) => {
312 let fn_def_id = self.resolver.definitions().local_def_id(id);
313 self.with_new_scopes(|this| {
314 this.current_item = Some(ident.span);
316 // Note: we don't need to change the return type from `T` to
317 // `impl Future<Output = T>` here because lower_body
318 // only cares about the input argument patterns in the function
319 // declaration (decl), not the return types.
320 let body_id = this.lower_maybe_async_body(
323 header.asyncness.node,
327 let (generics, decl) = this.add_in_band_defs(
330 AnonymousLifetimeMode::PassThrough,
331 |this, idty| this.lower_fn_decl(
333 Some((fn_def_id, idty)),
335 header.asyncness.node.opt_return_id()
338 let sig = hir::FnSig { decl, header: this.lower_fn_header(header) };
339 hir::ItemKind::Fn(sig, generics, body_id)
342 ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
343 ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
344 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
345 ItemKind::TyAlias(ref ty, ref generics) => match ty.kind.opaque_top_hack() {
347 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
348 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
349 hir::ItemKind::TyAlias(ty, generics)
352 let ty = hir::OpaqueTy {
353 generics: self.lower_generics(generics, ImplTraitContext::OpaqueTy(None)),
354 bounds: self.lower_param_bounds(bounds, ImplTraitContext::OpaqueTy(None)),
356 origin: hir::OpaqueTyOrigin::TypeAlias,
358 hir::ItemKind::OpaqueTy(ty)
361 ItemKind::Enum(ref enum_definition, ref generics) => {
364 variants: enum_definition
367 .map(|x| self.lower_variant(x))
370 self.lower_generics(generics, ImplTraitContext::disallowed()),
373 ItemKind::Struct(ref struct_def, ref generics) => {
374 let struct_def = self.lower_variant_data(struct_def);
375 hir::ItemKind::Struct(
377 self.lower_generics(generics, ImplTraitContext::disallowed()),
380 ItemKind::Union(ref vdata, ref generics) => {
381 let vdata = self.lower_variant_data(vdata);
382 hir::ItemKind::Union(
384 self.lower_generics(generics, ImplTraitContext::disallowed()),
396 let def_id = self.resolver.definitions().local_def_id(id);
398 // Lower the "impl header" first. This ordering is important
399 // for in-band lifetimes! Consider `'a` here:
401 // impl Foo<'a> for u32 {
402 // fn method(&'a self) { .. }
405 // Because we start by lowering the `Foo<'a> for u32`
406 // part, we will add `'a` to the list of generics on
407 // the impl. When we then encounter it later in the
408 // method, it will not be considered an in-band
409 // lifetime to be added, but rather a reference to a
411 let lowered_trait_impl_id = self.lower_node_id(id);
412 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
415 AnonymousLifetimeMode::CreateParameter,
417 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
418 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
421 if let Some(ref trait_ref) = trait_ref {
422 if let Res::Def(DefKind::Trait, def_id) = trait_ref.path.res {
423 this.trait_impls.entry(def_id).or_default().push(
424 lowered_trait_impl_id);
428 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
430 (trait_ref, lowered_ty)
434 let new_impl_items = self.with_in_scope_lifetime_defs(
435 &ast_generics.params,
439 .map(|item| this.lower_impl_item_ref(item))
447 self.lower_defaultness(defaultness, true /* [1] */),
454 ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
455 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
458 .map(|item| self.lower_trait_item_ref(item))
460 hir::ItemKind::Trait(
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(..)
473 | ItemKind::Mac(..) => bug!("`TyMac` should have been expanded by now"),
476 // [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to
477 // not cause an assertion failure inside the `lower_defaultness` function.
485 vis: &mut hir::Visibility,
487 attrs: &hir::HirVec<Attribute>,
489 debug!("lower_use_tree(tree={:?})", tree);
490 debug!("lower_use_tree: vis = {:?}", vis);
492 let path = &tree.prefix;
493 let segments = prefix
496 .chain(path.segments.iter())
501 UseTreeKind::Simple(rename, id1, id2) => {
502 *ident = tree.ident();
504 // First, apply the prefix to the path.
505 let mut path = Path {
510 // Correctly resolve `self` imports.
511 if path.segments.len() > 1
512 && path.segments.last().unwrap().ident.name == kw::SelfLower
514 let _ = path.segments.pop();
515 if rename.is_none() {
516 *ident = path.segments.last().unwrap().ident;
520 let mut resolutions = self.expect_full_res_from_use(id);
521 // We want to return *something* from this function, so hold onto the first item
523 let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
525 // Here, we are looping over namespaces, if they exist for the definition
526 // being imported. We only handle type and value namespaces because we
527 // won't be dealing with macros in the rest of the compiler.
528 // Essentially a single `use` which imports two names is desugared into
530 for (res, &new_node_id) in resolutions.zip([id1, id2].iter()) {
532 let mut path = path.clone();
533 for seg in &mut path.segments {
534 seg.id = self.resolver.next_node_id();
536 let span = path.span;
538 self.with_hir_id_owner(new_node_id, |this| {
539 let new_id = this.lower_node_id(new_node_id);
540 let res = this.lower_res(res);
542 this.lower_path_extra(res, &path, ParamMode::Explicit, None);
543 let kind = hir::ItemKind::Use(P(path), hir::UseKind::Single);
544 let vis = this.rebuild_vis(&vis);
550 attrs: attrs.into_iter().cloned().collect(),
559 let path = P(self.lower_path_extra(ret_res, &path, ParamMode::Explicit, None));
560 hir::ItemKind::Use(path, hir::UseKind::Single)
562 UseTreeKind::Glob => {
563 let path = P(self.lower_path(
571 hir::ItemKind::Use(path, hir::UseKind::Glob)
573 UseTreeKind::Nested(ref trees) => {
574 // Nested imports are desugared into simple imports.
575 // So, if we start with
578 // pub(x) use foo::{a, b};
581 // we will create three items:
584 // pub(x) use foo::a;
585 // pub(x) use foo::b;
586 // pub(x) use foo::{}; // <-- this is called the `ListStem`
589 // The first two are produced by recursively invoking
590 // `lower_use_tree` (and indeed there may be things
591 // like `use foo::{a::{b, c}}` and so forth). They
592 // wind up being directly added to
593 // `self.items`. However, the structure of this
594 // function also requires us to return one item, and
595 // for that we return the `{}` import (called the
600 span: prefix.span.to(path.span),
603 // Add all the nested `PathListItem`s to the HIR.
604 for &(ref use_tree, id) in trees {
605 let new_hir_id = self.lower_node_id(id);
607 let mut prefix = prefix.clone();
609 // Give the segments new node-ids since they are being cloned.
610 for seg in &mut prefix.segments {
611 seg.id = self.resolver.next_node_id();
614 // Each `use` import is an item and thus are owners of the
615 // names in the path. Up to this point the nested import is
616 // the current owner, since we want each desugared import to
617 // own its own names, we have to adjust the owner before
618 // lowering the rest of the import.
619 self.with_hir_id_owner(id, |this| {
620 let mut vis = this.rebuild_vis(&vis);
621 let mut ident = *ident;
623 let kind = this.lower_use_tree(use_tree,
634 attrs: attrs.into_iter().cloned().collect(),
643 // Subtle and a bit hacky: we lower the privacy level
644 // of the list stem to "private" most of the time, but
645 // not for "restricted" paths. The key thing is that
646 // we don't want it to stay as `pub` (with no caveats)
647 // because that affects rustdoc and also the lints
648 // about `pub` items. But we can't *always* make it
649 // private -- particularly not for restricted paths --
650 // because it contains node-ids that would then be
651 // unused, failing the check that HirIds are "densely
654 hir::VisibilityKind::Public |
655 hir::VisibilityKind::Crate(_) |
656 hir::VisibilityKind::Inherited => {
657 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
659 hir::VisibilityKind::Restricted { .. } => {
660 // Do nothing here, as described in the comment on the match.
664 let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
665 let res = self.lower_res(res);
666 let path = P(self.lower_path_extra(res, &prefix, ParamMode::Explicit, None));
667 hir::ItemKind::Use(path, hir::UseKind::ListStem)
672 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
673 /// many times in the HIR tree; for each occurrence, we need to assign distinct
674 /// `NodeId`s. (See, e.g., #56128.)
675 fn rebuild_use_path(&mut self, path: &hir::Path) -> hir::Path {
676 debug!("rebuild_use_path(path = {:?})", path);
677 let segments = path.segments.iter().map(|seg| hir::PathSegment {
679 hir_id: seg.hir_id.map(|_| self.next_id()),
682 infer_args: seg.infer_args,
691 fn rebuild_vis(&mut self, vis: &hir::Visibility) -> hir::Visibility {
692 let vis_kind = match vis.node {
693 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
694 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
695 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
696 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
697 hir::VisibilityKind::Restricted {
698 path: P(self.rebuild_use_path(path)),
699 hir_id: self.next_id(),
703 respan(vis.span, vis_kind)
706 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem {
707 let def_id = self.resolver.definitions().local_def_id(i.id);
709 hir_id: self.lower_node_id(i.id),
711 attrs: self.lower_attrs(&i.attrs),
713 ForeignItemKind::Fn(ref fdec, ref generics) => {
714 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
717 AnonymousLifetimeMode::PassThrough,
720 // Disallow `impl Trait` in foreign items.
721 this.lower_fn_decl(fdec, None, false, None),
722 this.lower_fn_params_to_names(fdec),
727 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
729 ForeignItemKind::Static(ref t, m) => {
730 hir::ForeignItemKind::Static(
731 self.lower_ty(t, ImplTraitContext::disallowed()), m)
733 ForeignItemKind::Ty => hir::ForeignItemKind::Type,
734 ForeignItemKind::Macro(_) => panic!("macro shouldn't exist here"),
736 vis: self.lower_visibility(&i.vis, None),
741 fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod {
743 abi: fm.abi.map_or(abi::Abi::C, |abi| self.lower_abi(abi)),
746 .map(|x| self.lower_foreign_item(x))
751 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> P<hir::GlobalAsm> {
752 P(hir::GlobalAsm { asm: ga.asm })
755 fn lower_variant(&mut self, v: &Variant) -> hir::Variant {
757 attrs: self.lower_attrs(&v.attrs),
758 data: self.lower_variant_data(&v.data),
759 disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
760 id: self.lower_node_id(v.id),
766 fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData {
768 VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
769 fields.iter().enumerate().map(|f| self.lower_struct_field(f)).collect(),
772 VariantData::Tuple(ref fields, id) => {
773 hir::VariantData::Tuple(
777 .map(|f| self.lower_struct_field(f))
779 self.lower_node_id(id),
782 VariantData::Unit(id) => {
783 hir::VariantData::Unit(self.lower_node_id(id))
788 fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField {
789 let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
790 let t = self.lower_path_ty(
794 ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
795 ImplTraitContext::disallowed()
799 self.lower_ty(&f.ty, ImplTraitContext::disallowed())
803 hir_id: self.lower_node_id(f.id),
804 ident: match f.ident {
805 Some(ident) => ident,
806 // FIXME(jseyfried): positional field hygiene.
807 None => Ident::new(sym::integer(index), f.span),
809 vis: self.lower_visibility(&f.vis, None),
811 attrs: self.lower_attrs(&f.attrs),
815 fn lower_trait_item(&mut self, i: &AssocItem) -> hir::TraitItem {
816 let trait_item_def_id = self.resolver.definitions().local_def_id(i.id);
818 let (generics, kind) = match i.kind {
819 AssocItemKind::Const(ref ty, ref default) => (
820 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
821 hir::TraitItemKind::Const(
822 self.lower_ty(ty, ImplTraitContext::disallowed()),
825 .map(|x| self.lower_const_body(i.span, Some(x))),
828 AssocItemKind::Fn(ref sig, None) => {
829 let names = self.lower_fn_params_to_names(&sig.decl);
830 let (generics, sig) = self.lower_method_sig(
837 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Required(names)))
839 AssocItemKind::Fn(ref sig, Some(ref body)) => {
840 let body_id = self.lower_fn_body_block(i.span, &sig.decl, Some(body));
841 let (generics, sig) = self.lower_method_sig(
848 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Provided(body_id)))
850 AssocItemKind::TyAlias(ref bounds, ref default) => {
851 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
852 let kind = hir::TraitItemKind::Type(
853 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
856 .map(|x| self.lower_ty(x, ImplTraitContext::disallowed())),
861 AssocItemKind::Macro(..) => bug!("macro item shouldn't exist at this point"),
865 hir_id: self.lower_node_id(i.id),
867 attrs: self.lower_attrs(&i.attrs),
874 fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef {
875 let (kind, has_default) = match i.kind {
876 AssocItemKind::Const(_, ref default) => {
877 (hir::AssocItemKind::Const, default.is_some())
879 AssocItemKind::TyAlias(_, ref default) => {
880 (hir::AssocItemKind::Type, default.is_some())
882 AssocItemKind::Fn(ref sig, ref default) => (
883 hir::AssocItemKind::Method {
884 has_self: sig.decl.has_self(),
888 AssocItemKind::Macro(..) => unimplemented!(),
891 id: hir::TraitItemId { hir_id: self.lower_node_id(i.id) },
894 defaultness: self.lower_defaultness(Defaultness::Default, has_default),
899 /// Construct `ExprKind::Err` for the given `span`.
900 fn expr_err(&mut self, span: Span) -> hir::Expr {
901 self.expr(span, hir::ExprKind::Err, AttrVec::new())
904 fn lower_impl_item(&mut self, i: &AssocItem) -> hir::ImplItem {
905 let impl_item_def_id = self.resolver.definitions().local_def_id(i.id);
907 let (generics, kind) = match i.kind {
908 AssocItemKind::Const(ref ty, ref expr) => (
909 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
910 hir::ImplItemKind::Const(
911 self.lower_ty(ty, ImplTraitContext::disallowed()),
912 self.lower_const_body(i.span, expr.as_deref()),
915 AssocItemKind::Fn(ref sig, ref body) => {
916 self.current_item = Some(i.span);
917 let body_id = self.lower_maybe_async_body(
920 sig.header.asyncness.node,
923 let impl_trait_return_allow = !self.is_in_trait_impl;
924 let (generics, sig) = self.lower_method_sig(
928 impl_trait_return_allow,
929 sig.header.asyncness.node.opt_return_id(),
932 (generics, hir::ImplItemKind::Method(sig, body_id))
934 AssocItemKind::TyAlias(_, ref ty) => {
935 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
936 let kind = match ty {
938 hir::ImplItemKind::TyAlias(P(self.ty(i.span, hir::TyKind::Err)))
940 Some(ty) => match ty.kind.opaque_top_hack() {
942 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
943 hir::ImplItemKind::TyAlias(ty)
946 let bs = self.lower_param_bounds(bs, ImplTraitContext::disallowed());
947 hir::ImplItemKind::OpaqueTy(bs)
953 AssocItemKind::Macro(..) => bug!("`TyMac` should have been expanded by now"),
957 hir_id: self.lower_node_id(i.id),
959 attrs: self.lower_attrs(&i.attrs),
961 vis: self.lower_visibility(&i.vis, None),
962 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
967 // [1] since `default impl` is not yet implemented, this is always true in impls
970 fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef {
972 id: hir::ImplItemId { hir_id: self.lower_node_id(i.id) },
975 vis: self.lower_visibility(&i.vis, Some(i.id)),
976 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
977 kind: match &i.kind {
978 AssocItemKind::Const(..) => hir::AssocItemKind::Const,
979 AssocItemKind::TyAlias(_, ty) => match ty
981 .and_then(|ty| ty.kind.opaque_top_hack())
983 None => hir::AssocItemKind::Type,
984 Some(_) => hir::AssocItemKind::OpaqueTy,
986 AssocItemKind::Fn(sig, _) => hir::AssocItemKind::Method {
987 has_self: sig.decl.has_self(),
989 AssocItemKind::Macro(..) => unimplemented!(),
993 // [1] since `default impl` is not yet implemented, this is always true in impls
996 /// If an `explicit_owner` is given, this method allocates the `HirId` in
997 /// the address space of that item instead of the item currently being
998 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
999 /// lower a `Visibility` value although we haven't lowered the owning
1000 /// `ImplItem` in question yet.
1001 fn lower_visibility(
1004 explicit_owner: Option<NodeId>,
1005 ) -> hir::Visibility {
1006 let node = match v.node {
1007 VisibilityKind::Public => hir::VisibilityKind::Public,
1008 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
1009 VisibilityKind::Restricted { ref path, id } => {
1010 debug!("lower_visibility: restricted path id = {:?}", id);
1011 let lowered_id = if let Some(owner) = explicit_owner {
1012 self.lower_node_id_with_owner(id, owner)
1014 self.lower_node_id(id)
1016 let res = self.expect_full_res(id);
1017 let res = self.lower_res(res);
1018 hir::VisibilityKind::Restricted {
1019 path: P(self.lower_path_extra(
1022 ParamMode::Explicit,
1028 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
1030 respan(v.span, node)
1033 fn lower_defaultness(&self, d: Defaultness, has_value: bool) -> hir::Defaultness {
1035 Defaultness::Default => hir::Defaultness::Default {
1036 has_value: has_value,
1038 Defaultness::Final => {
1040 hir::Defaultness::Final
1045 fn record_body(&mut self, params: HirVec<hir::Param>, value: hir::Expr) -> hir::BodyId {
1046 let body = hir::Body {
1047 generator_kind: self.generator_kind,
1052 self.bodies.insert(id, body);
1058 f: impl FnOnce(&mut LoweringContext<'_>) -> (HirVec<hir::Param>, hir::Expr),
1060 let prev_gen_kind = self.generator_kind.take();
1061 let (parameters, result) = f(self);
1062 let body_id = self.record_body(parameters, result);
1063 self.generator_kind = prev_gen_kind;
1067 fn lower_param(&mut self, param: &Param) -> hir::Param {
1069 attrs: self.lower_attrs(¶m.attrs),
1070 hir_id: self.lower_node_id(param.id),
1071 pat: self.lower_pat(¶m.pat),
1076 pub(super) fn lower_fn_body(
1079 body: impl FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
1081 self.lower_body(|this| (
1082 decl.inputs.iter().map(|x| this.lower_param(x)).collect(),
1087 fn lower_fn_body_block(
1091 body: Option<&Block>,
1093 self.lower_fn_body(decl, |this| this.lower_block_expr_opt(span, body))
1096 fn lower_block_expr_opt(&mut self, span: Span, block: Option<&Block>) -> hir::Expr {
1098 Some(block) => self.lower_block_expr(block),
1099 None => self.expr_err(span),
1103 pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
1104 self.lower_body(|this| (hir_vec![], match expr {
1105 Some(expr) => this.lower_expr(expr),
1106 None => this.expr_err(span),
1110 fn lower_maybe_async_body(
1115 body: Option<&Block>,
1117 let closure_id = match asyncness {
1118 IsAsync::Async { closure_id, .. } => closure_id,
1119 IsAsync::NotAsync => return self.lower_fn_body_block(span, decl, body),
1122 self.lower_body(|this| {
1123 let mut parameters: Vec<hir::Param> = Vec::new();
1124 let mut statements: Vec<hir::Stmt> = Vec::new();
1126 // Async function parameters are lowered into the closure body so that they are
1127 // captured and so that the drop order matches the equivalent non-async functions.
1131 // async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
1137 // fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
1139 // let __arg2 = __arg2;
1140 // let <pattern> = __arg2;
1141 // let __arg1 = __arg1;
1142 // let <pattern> = __arg1;
1143 // let __arg0 = __arg0;
1144 // let <pattern> = __arg0;
1145 // drop-temps { <body> } // see comments later in fn for details
1149 // If `<pattern>` is a simple ident, then it is lowered to a single
1150 // `let <pattern> = <pattern>;` statement as an optimization.
1152 // Note that the body is embedded in `drop-temps`; an
1153 // equivalent desugaring would be `return { <body>
1154 // };`. The key point is that we wish to drop all the
1155 // let-bound variables and temporaries created in the body
1156 // (and its tail expression!) before we drop the
1157 // parameters (c.f. rust-lang/rust#64512).
1158 for (index, parameter) in decl.inputs.iter().enumerate() {
1159 let parameter = this.lower_param(parameter);
1160 let span = parameter.pat.span;
1162 // Check if this is a binding pattern, if so, we can optimize and avoid adding a
1163 // `let <pat> = __argN;` statement. In this case, we do not rename the parameter.
1164 let (ident, is_simple_parameter) = match parameter.pat.kind {
1165 hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, ident, _) =>
1168 // Replace the ident for bindings that aren't simple.
1169 let name = format!("__arg{}", index);
1170 let ident = Ident::from_str(&name);
1176 let desugared_span =
1177 this.mark_span_with_reason(DesugaringKind::Async, span, None);
1179 // Construct a parameter representing `__argN: <ty>` to replace the parameter of the
1182 // If this is the simple case, this parameter will end up being the same as the
1183 // original parameter, but with a different pattern id.
1184 let mut stmt_attrs = AttrVec::new();
1185 stmt_attrs.extend(parameter.attrs.iter().cloned());
1186 let (new_parameter_pat, new_parameter_id) = this.pat_ident(desugared_span, ident);
1187 let new_parameter = hir::Param {
1188 attrs: parameter.attrs,
1189 hir_id: parameter.hir_id,
1190 pat: new_parameter_pat,
1191 span: parameter.span,
1195 if is_simple_parameter {
1196 // If this is the simple case, then we only insert one statement that is
1197 // `let <pat> = <pat>;`. We re-use the original argument's pattern so that
1198 // `HirId`s are densely assigned.
1199 let expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1200 let stmt = this.stmt_let_pat(
1205 hir::LocalSource::AsyncFn
1207 statements.push(stmt);
1209 // If this is not the simple case, then we construct two statements:
1212 // let __argN = __argN;
1213 // let <pat> = __argN;
1216 // The first statement moves the parameter into the closure and thus ensures
1217 // that the drop order is correct.
1219 // The second statement creates the bindings that the user wrote.
1221 // Construct the `let mut __argN = __argN;` statement. It must be a mut binding
1222 // because the user may have specified a `ref mut` binding in the next
1224 let (move_pat, move_id) = this.pat_ident_binding_mode(
1225 desugared_span, ident, hir::BindingAnnotation::Mutable);
1226 let move_expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1227 let move_stmt = this.stmt_let_pat(
1232 hir::LocalSource::AsyncFn
1235 // Construct the `let <pat> = __argN;` statement. We re-use the original
1236 // parameter's pattern so that `HirId`s are densely assigned.
1237 let pattern_expr = this.expr_ident(desugared_span, ident, move_id);
1238 let pattern_stmt = this.stmt_let_pat(
1241 Some(P(pattern_expr)),
1243 hir::LocalSource::AsyncFn
1246 statements.push(move_stmt);
1247 statements.push(pattern_stmt);
1250 parameters.push(new_parameter);
1253 let body_span = body.map_or(span, |b| b.span);
1254 let async_expr = this.make_async_expr(
1259 hir::AsyncGeneratorKind::Fn,
1261 // Create a block from the user's function body:
1262 let user_body = this.lower_block_expr_opt(body_span, body);
1264 // Transform into `drop-temps { <user-body> }`, an expression:
1265 let desugared_span = this.mark_span_with_reason(
1266 DesugaringKind::Async,
1270 let user_body = this.expr_drop_temps(
1276 // As noted above, create the final block like
1280 // let $param_pattern = $raw_param;
1282 // drop-temps { <user-body> }
1285 let body = this.block_all(
1290 this.expr_block(P(body), AttrVec::new())
1292 (HirVec::from(parameters), this.expr(body_span, async_expr, AttrVec::new()))
1296 fn lower_method_sig(
1298 generics: &Generics,
1301 impl_trait_return_allow: bool,
1302 is_async: Option<NodeId>,
1303 ) -> (hir::Generics, hir::FnSig) {
1304 let header = self.lower_fn_header(sig.header);
1305 let (generics, decl) = self.add_in_band_defs(
1308 AnonymousLifetimeMode::PassThrough,
1309 |this, idty| this.lower_fn_decl(
1311 Some((fn_def_id, idty)),
1312 impl_trait_return_allow,
1316 (generics, hir::FnSig { header, decl })
1319 fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
1321 unsafety: h.unsafety,
1322 asyncness: self.lower_asyncness(h.asyncness.node),
1323 constness: h.constness.node,
1324 abi: self.lower_extern(h.ext),
1328 pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
1329 abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
1330 self.error_on_invalid_abi(abi);
1335 pub(super) fn lower_extern(&mut self, ext: Extern) -> abi::Abi {
1337 Extern::None => abi::Abi::Rust,
1338 Extern::Implicit => abi::Abi::C,
1339 Extern::Explicit(abi) => self.lower_abi(abi),
1343 fn error_on_invalid_abi(&self, abi: StrLit) {
1348 "invalid ABI: found `{}`",
1351 .span_label(abi.span, "invalid ABI")
1352 .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
1356 fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
1358 IsAsync::Async { .. } => hir::IsAsync::Async,
1359 IsAsync::NotAsync => hir::IsAsync::NotAsync,
1363 pub(super) fn lower_generics(
1365 generics: &Generics,
1366 itctx: ImplTraitContext<'_>)
1369 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
1370 // FIXME: this could probably be done with less rightward drift. It also looks like two
1371 // control paths where `report_error` is called are the only paths that advance to after the
1372 // match statement, so the error reporting could probably just be moved there.
1373 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
1374 for pred in &generics.where_clause.predicates {
1375 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
1376 'next_bound: for bound in &bound_pred.bounds {
1377 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
1378 let report_error = |this: &mut Self| {
1379 this.diagnostic().span_err(
1380 bound_pred.bounded_ty.span,
1381 "`?Trait` bounds are only permitted at the \
1382 point where a type parameter is declared",
1385 // Check if the where clause type is a plain type parameter.
1386 match bound_pred.bounded_ty.kind {
1387 TyKind::Path(None, ref path)
1388 if path.segments.len() == 1
1389 && bound_pred.bound_generic_params.is_empty() =>
1391 if let Some(Res::Def(DefKind::TyParam, def_id)) = self.resolver
1392 .get_partial_res(bound_pred.bounded_ty.id)
1393 .map(|d| d.base_res())
1395 if let Some(node_id) =
1396 self.resolver.definitions().as_local_node_id(def_id)
1398 for param in &generics.params {
1400 GenericParamKind::Type { .. } => {
1401 if node_id == param.id {
1402 add_bounds.entry(param.id)
1404 .push(bound.clone());
1405 continue 'next_bound;
1415 _ => report_error(self),
1423 params: self.lower_generic_params(&generics.params, &add_bounds, itctx),
1424 where_clause: self.lower_where_clause(&generics.where_clause),
1425 span: generics.span,
1429 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause {
1430 self.with_anonymous_lifetime_mode(
1431 AnonymousLifetimeMode::ReportError,
1434 predicates: wc.predicates
1436 .map(|predicate| this.lower_where_predicate(predicate))
1444 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate {
1446 WherePredicate::BoundPredicate(WhereBoundPredicate {
1447 ref bound_generic_params,
1452 self.with_in_scope_lifetime_defs(
1453 &bound_generic_params,
1455 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
1456 bound_generic_params: this.lower_generic_params(
1457 bound_generic_params,
1458 &NodeMap::default(),
1459 ImplTraitContext::disallowed(),
1461 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
1464 .filter_map(|bound| match *bound {
1465 // Ignore `?Trait` bounds.
1466 // They were copied into type parameters already.
1467 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1468 _ => Some(this.lower_param_bound(
1470 ImplTraitContext::disallowed(),
1479 WherePredicate::RegionPredicate(WhereRegionPredicate {
1483 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
1485 lifetime: self.lower_lifetime(lifetime),
1486 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
1488 WherePredicate::EqPredicate(WhereEqPredicate {
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()),