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<'a, 'lowering, 'hir> {
28 pub(super) lctx: &'a mut LoweringContext<'lowering, 'hir>,
31 impl<'a, 'lowering, 'hir> ItemLowerer<'a, 'lowering, 'hir> {
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<'a, 'lowering, 'hir> Visitor<'a> for ItemLowerer<'a, 'lowering, 'hir> {
48 fn visit_mod(&mut self, m: &'a 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: &'a 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: &'a 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: &'a 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<'_, 'hir> {
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<'hir>> {
229 let mut ident = i.ident;
230 let mut vis = self.lower_visibility(&i.vis, None);
231 let attrs = self.lower_attrs_arena(&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.iter().cloned());
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 [Attribute],
270 vis: &mut hir::Visibility,
272 ) -> hir::ItemKind<'hir> {
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 let ty = self.lower_ty(
287 if self.sess.features_untracked().impl_trait_in_bindings {
288 ImplTraitContext::OpaqueTy(None)
290 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
293 hir::ItemKind::Static(
294 self.arena.alloc(ty.into_inner()),
296 self.lower_const_body(span, Some(e)),
299 ItemKind::Const(ref t, ref e) => {
300 let ty = self.lower_ty(
302 if self.sess.features_untracked().impl_trait_in_bindings {
303 ImplTraitContext::OpaqueTy(None)
305 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
308 hir::ItemKind::Const(
309 self.arena.alloc(ty.into_inner()),
310 self.lower_const_body(span, Some(e))
313 ItemKind::Fn(FnSig { ref decl, header }, ref generics, ref body) => {
314 let fn_def_id = self.resolver.definitions().local_def_id(id);
315 self.with_new_scopes(|this| {
316 this.current_item = Some(ident.span);
318 // Note: we don't need to change the return type from `T` to
319 // `impl Future<Output = T>` here because lower_body
320 // only cares about the input argument patterns in the function
321 // declaration (decl), not the return types.
322 let body_id = this.lower_maybe_async_body(
325 header.asyncness.node,
329 let (generics, decl) = this.add_in_band_defs(
332 AnonymousLifetimeMode::PassThrough,
333 |this, idty| this.lower_fn_decl(
335 Some((fn_def_id, idty)),
337 header.asyncness.node.opt_return_id()
340 let sig = hir::FnSig { decl, header: this.lower_fn_header(header) };
341 hir::ItemKind::Fn(sig, generics, body_id)
344 ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
345 ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
346 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
347 ItemKind::TyAlias(ref ty, ref generics) => match ty.kind.opaque_top_hack() {
349 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
350 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
351 hir::ItemKind::TyAlias(self.arena.alloc(ty.into_inner()), generics)
354 let ty = hir::OpaqueTy {
355 generics: self.lower_generics(generics, ImplTraitContext::OpaqueTy(None)),
356 bounds: self.lower_param_bounds(bounds, ImplTraitContext::OpaqueTy(None)),
358 origin: hir::OpaqueTyOrigin::TypeAlias,
360 hir::ItemKind::OpaqueTy(ty)
363 ItemKind::Enum(ref enum_definition, ref generics) => {
366 variants: self.arena.alloc_from_iter(
370 .map(|x| self.lower_variant(x))
373 self.lower_generics(generics, ImplTraitContext::disallowed()),
376 ItemKind::Struct(ref struct_def, ref generics) => {
377 let struct_def = self.lower_variant_data(struct_def);
378 hir::ItemKind::Struct(
380 self.lower_generics(generics, ImplTraitContext::disallowed()),
383 ItemKind::Union(ref vdata, ref generics) => {
384 let vdata = self.lower_variant_data(vdata);
385 hir::ItemKind::Union(
387 self.lower_generics(generics, ImplTraitContext::disallowed()),
399 let def_id = self.resolver.definitions().local_def_id(id);
401 // Lower the "impl header" first. This ordering is important
402 // for in-band lifetimes! Consider `'a` here:
404 // impl Foo<'a> for u32 {
405 // fn method(&'a self) { .. }
408 // Because we start by lowering the `Foo<'a> for u32`
409 // part, we will add `'a` to the list of generics on
410 // the impl. When we then encounter it later in the
411 // method, it will not be considered an in-band
412 // lifetime to be added, but rather a reference to a
414 let lowered_trait_impl_id = self.lower_node_id(id);
415 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
418 AnonymousLifetimeMode::CreateParameter,
420 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
421 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
424 if let Some(ref trait_ref) = trait_ref {
425 if let Res::Def(DefKind::Trait, def_id) = trait_ref.path.res {
426 this.trait_impls.entry(def_id).or_default().push(
427 lowered_trait_impl_id);
431 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
433 (trait_ref, lowered_ty)
437 let new_impl_items = self.with_in_scope_lifetime_defs(
438 &ast_generics.params,
440 this.arena.alloc_from_iter(
443 .map(|item| this.lower_impl_item_ref(item))
451 self.lower_defaultness(defaultness, true /* [1] */),
454 self.arena.alloc(lowered_ty.into_inner()),
458 ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
459 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
460 let items = self.arena.alloc_from_iter(items
462 .map(|item| self.lower_trait_item_ref(item))
464 hir::ItemKind::Trait(
467 self.lower_generics(generics, ImplTraitContext::disallowed()),
472 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
473 self.lower_generics(generics, ImplTraitContext::disallowed()),
474 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
476 ItemKind::MacroDef(..)
477 | ItemKind::Mac(..) => bug!("`TyMac` should have been expanded by now"),
480 // [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to
481 // not cause an assertion failure inside the `lower_defaultness` function.
489 vis: &mut hir::Visibility,
491 attrs: &'hir [Attribute],
492 ) -> hir::ItemKind<'hir> {
493 debug!("lower_use_tree(tree={:?})", tree);
494 debug!("lower_use_tree: vis = {:?}", vis);
496 let path = &tree.prefix;
497 let segments = prefix
500 .chain(path.segments.iter())
505 UseTreeKind::Simple(rename, id1, id2) => {
506 *ident = tree.ident();
508 // First, apply the prefix to the path.
509 let mut path = Path {
514 // Correctly resolve `self` imports.
515 if path.segments.len() > 1
516 && path.segments.last().unwrap().ident.name == kw::SelfLower
518 let _ = path.segments.pop();
519 if rename.is_none() {
520 *ident = path.segments.last().unwrap().ident;
524 let mut resolutions = self.expect_full_res_from_use(id);
525 // We want to return *something* from this function, so hold onto the first item
527 let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
529 // Here, we are looping over namespaces, if they exist for the definition
530 // being imported. We only handle type and value namespaces because we
531 // won't be dealing with macros in the rest of the compiler.
532 // Essentially a single `use` which imports two names is desugared into
534 for (res, &new_node_id) in resolutions.zip([id1, id2].iter()) {
536 let mut path = path.clone();
537 for seg in &mut path.segments {
538 seg.id = self.resolver.next_node_id();
540 let span = path.span;
542 self.with_hir_id_owner(new_node_id, |this| {
543 let new_id = this.lower_node_id(new_node_id);
544 let res = this.lower_res(res);
546 this.lower_path_extra(res, &path, ParamMode::Explicit, None);
547 let kind = hir::ItemKind::Use(this.arena.alloc(path), hir::UseKind::Single);
548 let vis = this.rebuild_vis(&vis);
563 let path = self.arena.alloc(self.lower_path_extra(ret_res, &path, ParamMode::Explicit, None));
564 hir::ItemKind::Use(path, hir::UseKind::Single)
566 UseTreeKind::Glob => {
567 let path = self.arena.alloc(self.lower_path(
575 hir::ItemKind::Use(path, hir::UseKind::Glob)
577 UseTreeKind::Nested(ref trees) => {
578 // Nested imports are desugared into simple imports.
579 // So, if we start with
582 // pub(x) use foo::{a, b};
585 // we will create three items:
588 // pub(x) use foo::a;
589 // pub(x) use foo::b;
590 // pub(x) use foo::{}; // <-- this is called the `ListStem`
593 // The first two are produced by recursively invoking
594 // `lower_use_tree` (and indeed there may be things
595 // like `use foo::{a::{b, c}}` and so forth). They
596 // wind up being directly added to
597 // `self.items`. However, the structure of this
598 // function also requires us to return one item, and
599 // for that we return the `{}` import (called the
604 span: prefix.span.to(path.span),
607 // Add all the nested `PathListItem`s to the HIR.
608 for &(ref use_tree, id) in trees {
609 let new_hir_id = self.lower_node_id(id);
611 let mut prefix = prefix.clone();
613 // Give the segments new node-ids since they are being cloned.
614 for seg in &mut prefix.segments {
615 seg.id = self.resolver.next_node_id();
618 // Each `use` import is an item and thus are owners of the
619 // names in the path. Up to this point the nested import is
620 // the current owner, since we want each desugared import to
621 // own its own names, we have to adjust the owner before
622 // lowering the rest of the import.
623 self.with_hir_id_owner(id, |this| {
624 let mut vis = this.rebuild_vis(&vis);
625 let mut ident = *ident;
627 let kind = this.lower_use_tree(use_tree,
647 // Subtle and a bit hacky: we lower the privacy level
648 // of the list stem to "private" most of the time, but
649 // not for "restricted" paths. The key thing is that
650 // we don't want it to stay as `pub` (with no caveats)
651 // because that affects rustdoc and also the lints
652 // about `pub` items. But we can't *always* make it
653 // private -- particularly not for restricted paths --
654 // because it contains node-ids that would then be
655 // unused, failing the check that HirIds are "densely
658 hir::VisibilityKind::Public |
659 hir::VisibilityKind::Crate(_) |
660 hir::VisibilityKind::Inherited => {
661 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
663 hir::VisibilityKind::Restricted { .. } => {
664 // Do nothing here, as described in the comment on the match.
668 let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
669 let res = self.lower_res(res);
670 let path = self.arena.alloc(self.lower_path_extra(res, &prefix, ParamMode::Explicit, None));
671 hir::ItemKind::Use(path, hir::UseKind::ListStem)
676 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
677 /// many times in the HIR tree; for each occurrence, we need to assign distinct
678 /// `NodeId`s. (See, e.g., #56128.)
679 fn rebuild_use_path(&mut self, path: &hir::Path) -> hir::Path {
680 debug!("rebuild_use_path(path = {:?})", path);
681 let segments = path.segments.iter().map(|seg| hir::PathSegment {
683 hir_id: seg.hir_id.map(|_| self.next_id()),
686 infer_args: seg.infer_args,
695 fn rebuild_vis(&mut self, vis: &hir::Visibility) -> hir::Visibility {
696 let vis_kind = match vis.node {
697 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
698 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
699 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
700 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
701 hir::VisibilityKind::Restricted {
702 path: P(self.rebuild_use_path(path)),
703 hir_id: self.next_id(),
707 respan(vis.span, vis_kind)
710 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem<'hir> {
711 let def_id = self.resolver.definitions().local_def_id(i.id);
713 hir_id: self.lower_node_id(i.id),
715 attrs: self.lower_attrs_arena(&i.attrs),
717 ForeignItemKind::Fn(ref fdec, ref generics) => {
718 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
721 AnonymousLifetimeMode::PassThrough,
724 // Disallow `impl Trait` in foreign items.
725 this.lower_fn_decl(fdec, None, false, None),
726 this.lower_fn_params_to_names(fdec),
730 let fn_dec = self.arena.alloc(fn_dec.into_inner());
731 let fn_args = self.arena.alloc_from_iter(fn_args.into_iter());
733 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
735 ForeignItemKind::Static(ref t, m) => {
736 hir::ForeignItemKind::Static(
737 self.arena.alloc(self.lower_ty(t, ImplTraitContext::disallowed()).into_inner()), m)
739 ForeignItemKind::Ty => hir::ForeignItemKind::Type,
740 ForeignItemKind::Macro(_) => panic!("macro shouldn't exist here"),
742 vis: self.lower_visibility(&i.vis, None),
747 fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod<'hir> {
749 abi: fm.abi.map_or(abi::Abi::C, |abi| self.lower_abi(abi)),
750 items: self.arena.alloc_from_iter(fm.items
752 .map(|x| self.lower_foreign_item(x))),
756 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> &'hir hir::GlobalAsm {
757 self.arena.alloc(hir::GlobalAsm { asm: ga.asm })
760 fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> {
762 attrs: self.lower_attrs_arena(&v.attrs),
763 data: self.lower_variant_data(&v.data),
764 disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
765 id: self.lower_node_id(v.id),
771 fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData<'hir> {
773 VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
774 self.arena.alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_struct_field(f))),
777 VariantData::Tuple(ref fields, id) => {
778 hir::VariantData::Tuple(
779 self.arena.alloc_from_iter(
783 .map(|f| self.lower_struct_field(f))
785 self.lower_node_id(id),
788 VariantData::Unit(id) => {
789 hir::VariantData::Unit(self.lower_node_id(id))
794 fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField {
795 let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
796 let t = self.lower_path_ty(
800 ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
801 ImplTraitContext::disallowed()
805 self.lower_ty(&f.ty, ImplTraitContext::disallowed())
809 hir_id: self.lower_node_id(f.id),
810 ident: match f.ident {
811 Some(ident) => ident,
812 // FIXME(jseyfried): positional field hygiene.
813 None => Ident::new(sym::integer(index), f.span),
815 vis: self.lower_visibility(&f.vis, None),
817 attrs: self.lower_attrs(&f.attrs),
821 fn lower_trait_item(&mut self, i: &AssocItem) -> hir::TraitItem<'hir> {
822 let trait_item_def_id = self.resolver.definitions().local_def_id(i.id);
824 let (generics, kind) = match i.kind {
825 AssocItemKind::Const(ref ty, ref default) => (
826 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
827 hir::TraitItemKind::Const(
828 self.arena.alloc(self.lower_ty(ty, ImplTraitContext::disallowed()).into_inner()),
831 .map(|x| self.lower_const_body(i.span, Some(x))),
834 AssocItemKind::Fn(ref sig, None) => {
835 let names = self.lower_fn_params_to_names(&sig.decl);
836 let (generics, sig) = self.lower_method_sig(
843 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Required(names)))
845 AssocItemKind::Fn(ref sig, Some(ref body)) => {
846 let body_id = self.lower_fn_body_block(i.span, &sig.decl, Some(body));
847 let (generics, sig) = self.lower_method_sig(
854 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Provided(body_id)))
856 AssocItemKind::TyAlias(ref bounds, ref default) => {
857 let ty = default.as_ref().map(|x| -> &'hir hir::Ty { self.arena.alloc(
858 self.lower_ty(x, ImplTraitContext::disallowed()).into_inner())
860 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
861 let kind = hir::TraitItemKind::Type(
862 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
868 AssocItemKind::Macro(..) => bug!("macro item shouldn't exist at this point"),
872 hir_id: self.lower_node_id(i.id),
874 attrs: self.lower_attrs_arena(&i.attrs),
881 fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef {
882 let (kind, has_default) = match i.kind {
883 AssocItemKind::Const(_, ref default) => {
884 (hir::AssocItemKind::Const, default.is_some())
886 AssocItemKind::TyAlias(_, ref default) => {
887 (hir::AssocItemKind::Type, default.is_some())
889 AssocItemKind::Fn(ref sig, ref default) => (
890 hir::AssocItemKind::Method {
891 has_self: sig.decl.has_self(),
895 AssocItemKind::Macro(..) => unimplemented!(),
898 id: hir::TraitItemId { hir_id: self.lower_node_id(i.id) },
901 defaultness: self.lower_defaultness(Defaultness::Default, has_default),
906 /// Construct `ExprKind::Err` for the given `span`.
907 fn expr_err(&mut self, span: Span) -> hir::Expr {
908 self.expr(span, hir::ExprKind::Err, AttrVec::new())
911 fn lower_impl_item(&mut self, i: &AssocItem) -> hir::ImplItem<'hir> {
912 let impl_item_def_id = self.resolver.definitions().local_def_id(i.id);
914 let (generics, kind) = match i.kind {
915 AssocItemKind::Const(ref ty, ref expr) => (
916 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
917 hir::ImplItemKind::Const(
918 self.arena.alloc(self.lower_ty(ty, ImplTraitContext::disallowed()).into_inner()),
919 self.lower_const_body(i.span, expr.as_deref()),
922 AssocItemKind::Fn(ref sig, ref body) => {
923 self.current_item = Some(i.span);
924 let body_id = self.lower_maybe_async_body(
927 sig.header.asyncness.node,
930 let impl_trait_return_allow = !self.is_in_trait_impl;
931 let (generics, sig) = self.lower_method_sig(
935 impl_trait_return_allow,
936 sig.header.asyncness.node.opt_return_id(),
939 (generics, hir::ImplItemKind::Method(sig, body_id))
941 AssocItemKind::TyAlias(_, ref ty) => {
942 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
943 let kind = match ty {
945 let ty = self.arena.alloc(self.ty(i.span, hir::TyKind::Err));
946 hir::ImplItemKind::TyAlias(ty)
948 Some(ty) => match ty.kind.opaque_top_hack() {
950 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
951 let ty = self.arena.alloc(ty.into_inner());
952 hir::ImplItemKind::TyAlias(ty)
955 let bs = self.lower_param_bounds(bs, ImplTraitContext::disallowed());
956 hir::ImplItemKind::OpaqueTy(bs)
962 AssocItemKind::Macro(..) => bug!("`TyMac` should have been expanded by now"),
966 hir_id: self.lower_node_id(i.id),
968 attrs: self.lower_attrs_arena(&i.attrs),
970 vis: self.lower_visibility(&i.vis, None),
971 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
976 // [1] since `default impl` is not yet implemented, this is always true in impls
979 fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef {
981 id: hir::ImplItemId { hir_id: self.lower_node_id(i.id) },
984 vis: self.lower_visibility(&i.vis, Some(i.id)),
985 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
986 kind: match &i.kind {
987 AssocItemKind::Const(..) => hir::AssocItemKind::Const,
988 AssocItemKind::TyAlias(_, ty) => match ty
990 .and_then(|ty| ty.kind.opaque_top_hack())
992 None => hir::AssocItemKind::Type,
993 Some(_) => hir::AssocItemKind::OpaqueTy,
995 AssocItemKind::Fn(sig, _) => hir::AssocItemKind::Method {
996 has_self: sig.decl.has_self(),
998 AssocItemKind::Macro(..) => unimplemented!(),
1002 // [1] since `default impl` is not yet implemented, this is always true in impls
1005 /// If an `explicit_owner` is given, this method allocates the `HirId` in
1006 /// the address space of that item instead of the item currently being
1007 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
1008 /// lower a `Visibility` value although we haven't lowered the owning
1009 /// `ImplItem` in question yet.
1010 fn lower_visibility(
1013 explicit_owner: Option<NodeId>,
1014 ) -> hir::Visibility {
1015 let node = match v.node {
1016 VisibilityKind::Public => hir::VisibilityKind::Public,
1017 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
1018 VisibilityKind::Restricted { ref path, id } => {
1019 debug!("lower_visibility: restricted path id = {:?}", id);
1020 let lowered_id = if let Some(owner) = explicit_owner {
1021 self.lower_node_id_with_owner(id, owner)
1023 self.lower_node_id(id)
1025 let res = self.expect_full_res(id);
1026 let res = self.lower_res(res);
1027 hir::VisibilityKind::Restricted {
1028 path: P(self.lower_path_extra(
1031 ParamMode::Explicit,
1037 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
1039 respan(v.span, node)
1042 fn lower_defaultness(&self, d: Defaultness, has_value: bool) -> hir::Defaultness {
1044 Defaultness::Default => hir::Defaultness::Default {
1045 has_value: has_value,
1047 Defaultness::Final => {
1049 hir::Defaultness::Final
1054 fn record_body(&mut self, params: HirVec<hir::Param>, value: hir::Expr) -> hir::BodyId {
1055 let body = hir::Body {
1056 generator_kind: self.generator_kind,
1061 self.bodies.insert(id, body);
1067 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> (HirVec<hir::Param>, hir::Expr),
1069 let prev_gen_kind = self.generator_kind.take();
1070 let (parameters, result) = f(self);
1071 let body_id = self.record_body(parameters, result);
1072 self.generator_kind = prev_gen_kind;
1076 fn lower_param(&mut self, param: &Param) -> hir::Param {
1078 attrs: self.lower_attrs(¶m.attrs),
1079 hir_id: self.lower_node_id(param.id),
1080 pat: self.lower_pat(¶m.pat),
1085 pub(super) fn lower_fn_body(
1088 body: impl FnOnce(&mut LoweringContext<'_, '_>) -> hir::Expr,
1090 self.lower_body(|this| (
1091 decl.inputs.iter().map(|x| this.lower_param(x)).collect(),
1096 fn lower_fn_body_block(
1100 body: Option<&Block>,
1102 self.lower_fn_body(decl, |this| this.lower_block_expr_opt(span, body))
1105 fn lower_block_expr_opt(&mut self, span: Span, block: Option<&Block>) -> hir::Expr {
1107 Some(block) => self.lower_block_expr(block),
1108 None => self.expr_err(span),
1112 pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
1113 self.lower_body(|this| (hir_vec![], match expr {
1114 Some(expr) => this.lower_expr(expr),
1115 None => this.expr_err(span),
1119 fn lower_maybe_async_body(
1124 body: Option<&Block>,
1126 let closure_id = match asyncness {
1127 IsAsync::Async { closure_id, .. } => closure_id,
1128 IsAsync::NotAsync => return self.lower_fn_body_block(span, decl, body),
1131 self.lower_body(|this| {
1132 let mut parameters: Vec<hir::Param> = Vec::new();
1133 let mut statements: Vec<hir::Stmt> = Vec::new();
1135 // Async function parameters are lowered into the closure body so that they are
1136 // captured and so that the drop order matches the equivalent non-async functions.
1140 // async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
1146 // fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
1148 // let __arg2 = __arg2;
1149 // let <pattern> = __arg2;
1150 // let __arg1 = __arg1;
1151 // let <pattern> = __arg1;
1152 // let __arg0 = __arg0;
1153 // let <pattern> = __arg0;
1154 // drop-temps { <body> } // see comments later in fn for details
1158 // If `<pattern>` is a simple ident, then it is lowered to a single
1159 // `let <pattern> = <pattern>;` statement as an optimization.
1161 // Note that the body is embedded in `drop-temps`; an
1162 // equivalent desugaring would be `return { <body>
1163 // };`. The key point is that we wish to drop all the
1164 // let-bound variables and temporaries created in the body
1165 // (and its tail expression!) before we drop the
1166 // parameters (c.f. rust-lang/rust#64512).
1167 for (index, parameter) in decl.inputs.iter().enumerate() {
1168 let parameter = this.lower_param(parameter);
1169 let span = parameter.pat.span;
1171 // Check if this is a binding pattern, if so, we can optimize and avoid adding a
1172 // `let <pat> = __argN;` statement. In this case, we do not rename the parameter.
1173 let (ident, is_simple_parameter) = match parameter.pat.kind {
1174 hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, ident, _) =>
1177 // Replace the ident for bindings that aren't simple.
1178 let name = format!("__arg{}", index);
1179 let ident = Ident::from_str(&name);
1185 let desugared_span =
1186 this.mark_span_with_reason(DesugaringKind::Async, span, None);
1188 // Construct a parameter representing `__argN: <ty>` to replace the parameter of the
1191 // If this is the simple case, this parameter will end up being the same as the
1192 // original parameter, but with a different pattern id.
1193 let mut stmt_attrs = AttrVec::new();
1194 stmt_attrs.extend(parameter.attrs.iter().cloned());
1195 let (new_parameter_pat, new_parameter_id) = this.pat_ident(desugared_span, ident);
1196 let new_parameter = hir::Param {
1197 attrs: parameter.attrs,
1198 hir_id: parameter.hir_id,
1199 pat: new_parameter_pat,
1200 span: parameter.span,
1204 if is_simple_parameter {
1205 // If this is the simple case, then we only insert one statement that is
1206 // `let <pat> = <pat>;`. We re-use the original argument's pattern so that
1207 // `HirId`s are densely assigned.
1208 let expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1209 let stmt = this.stmt_let_pat(
1214 hir::LocalSource::AsyncFn
1216 statements.push(stmt);
1218 // If this is not the simple case, then we construct two statements:
1221 // let __argN = __argN;
1222 // let <pat> = __argN;
1225 // The first statement moves the parameter into the closure and thus ensures
1226 // that the drop order is correct.
1228 // The second statement creates the bindings that the user wrote.
1230 // Construct the `let mut __argN = __argN;` statement. It must be a mut binding
1231 // because the user may have specified a `ref mut` binding in the next
1233 let (move_pat, move_id) = this.pat_ident_binding_mode(
1234 desugared_span, ident, hir::BindingAnnotation::Mutable);
1235 let move_expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1236 let move_stmt = this.stmt_let_pat(
1241 hir::LocalSource::AsyncFn
1244 // Construct the `let <pat> = __argN;` statement. We re-use the original
1245 // parameter's pattern so that `HirId`s are densely assigned.
1246 let pattern_expr = this.expr_ident(desugared_span, ident, move_id);
1247 let pattern_stmt = this.stmt_let_pat(
1250 Some(P(pattern_expr)),
1252 hir::LocalSource::AsyncFn
1255 statements.push(move_stmt);
1256 statements.push(pattern_stmt);
1259 parameters.push(new_parameter);
1262 let body_span = body.map_or(span, |b| b.span);
1263 let async_expr = this.make_async_expr(
1268 hir::AsyncGeneratorKind::Fn,
1270 // Create a block from the user's function body:
1271 let user_body = this.lower_block_expr_opt(body_span, body);
1273 // Transform into `drop-temps { <user-body> }`, an expression:
1274 let desugared_span = this.mark_span_with_reason(
1275 DesugaringKind::Async,
1279 let user_body = this.expr_drop_temps(
1285 // As noted above, create the final block like
1289 // let $param_pattern = $raw_param;
1291 // drop-temps { <user-body> }
1294 let body = this.block_all(
1299 this.expr_block(P(body), AttrVec::new())
1301 (HirVec::from(parameters), this.expr(body_span, async_expr, AttrVec::new()))
1305 fn lower_method_sig(
1307 generics: &Generics,
1310 impl_trait_return_allow: bool,
1311 is_async: Option<NodeId>,
1312 ) -> (hir::Generics, hir::FnSig) {
1313 let header = self.lower_fn_header(sig.header);
1314 let (generics, decl) = self.add_in_band_defs(
1317 AnonymousLifetimeMode::PassThrough,
1318 |this, idty| this.lower_fn_decl(
1320 Some((fn_def_id, idty)),
1321 impl_trait_return_allow,
1325 (generics, hir::FnSig { header, decl })
1328 fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
1330 unsafety: h.unsafety,
1331 asyncness: self.lower_asyncness(h.asyncness.node),
1332 constness: h.constness.node,
1333 abi: self.lower_extern(h.ext),
1337 pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
1338 abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
1339 self.error_on_invalid_abi(abi);
1344 pub(super) fn lower_extern(&mut self, ext: Extern) -> abi::Abi {
1346 Extern::None => abi::Abi::Rust,
1347 Extern::Implicit => abi::Abi::C,
1348 Extern::Explicit(abi) => self.lower_abi(abi),
1352 fn error_on_invalid_abi(&self, abi: StrLit) {
1357 "invalid ABI: found `{}`",
1360 .span_label(abi.span, "invalid ABI")
1361 .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
1365 fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
1367 IsAsync::Async { .. } => hir::IsAsync::Async,
1368 IsAsync::NotAsync => hir::IsAsync::NotAsync,
1372 pub(super) fn lower_generics(
1374 generics: &Generics,
1375 itctx: ImplTraitContext<'_>)
1378 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
1379 // FIXME: this could probably be done with less rightward drift. It also looks like two
1380 // control paths where `report_error` is called are the only paths that advance to after the
1381 // match statement, so the error reporting could probably just be moved there.
1382 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
1383 for pred in &generics.where_clause.predicates {
1384 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
1385 'next_bound: for bound in &bound_pred.bounds {
1386 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
1387 let report_error = |this: &mut Self| {
1388 this.diagnostic().span_err(
1389 bound_pred.bounded_ty.span,
1390 "`?Trait` bounds are only permitted at the \
1391 point where a type parameter is declared",
1394 // Check if the where clause type is a plain type parameter.
1395 match bound_pred.bounded_ty.kind {
1396 TyKind::Path(None, ref path)
1397 if path.segments.len() == 1
1398 && bound_pred.bound_generic_params.is_empty() =>
1400 if let Some(Res::Def(DefKind::TyParam, def_id)) = self.resolver
1401 .get_partial_res(bound_pred.bounded_ty.id)
1402 .map(|d| d.base_res())
1404 if let Some(node_id) =
1405 self.resolver.definitions().as_local_node_id(def_id)
1407 for param in &generics.params {
1409 GenericParamKind::Type { .. } => {
1410 if node_id == param.id {
1411 add_bounds.entry(param.id)
1413 .push(bound.clone());
1414 continue 'next_bound;
1424 _ => report_error(self),
1432 params: self.lower_generic_params(&generics.params, &add_bounds, itctx),
1433 where_clause: self.lower_where_clause(&generics.where_clause),
1434 span: generics.span,
1438 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause {
1439 self.with_anonymous_lifetime_mode(
1440 AnonymousLifetimeMode::ReportError,
1443 predicates: wc.predicates
1445 .map(|predicate| this.lower_where_predicate(predicate))
1453 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate {
1455 WherePredicate::BoundPredicate(WhereBoundPredicate {
1456 ref bound_generic_params,
1461 self.with_in_scope_lifetime_defs(
1462 &bound_generic_params,
1464 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
1465 bound_generic_params: this.lower_generic_params(
1466 bound_generic_params,
1467 &NodeMap::default(),
1468 ImplTraitContext::disallowed(),
1470 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
1473 .filter_map(|bound| match *bound {
1474 // Ignore `?Trait` bounds.
1475 // They were copied into type parameters already.
1476 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1477 _ => Some(this.lower_param_bound(
1479 ImplTraitContext::disallowed(),
1488 WherePredicate::RegionPredicate(WhereRegionPredicate {
1492 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
1494 lifetime: self.lower_lifetime(lifetime),
1495 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
1497 WherePredicate::EqPredicate(WhereEqPredicate {
1503 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
1504 hir_id: self.lower_node_id(id),
1505 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
1506 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),